What to Eat & Take While on a GLP-1: The Complete GLP-1 Nutrition & Supplement Guide

How Do GLP-1 Medications Work?

GLP-1 is a hormone that our bodies naturally make after we eat. It helps control blood sugar, digestion, hunger, and how much food we eat. GLP-1 medications work by mimicking this natural hormone in the body. Medications, such as tirzepatide and semaglutide, work to help control blood sugar and appetite.¹

One of the main ways GLP-1 medications work is by affecting the parts of the brain that control hunger and fullness. These medications can help reduce hunger and make you feel full sooner and for a longer period of time. As a result, many people find that they can eat smaller amounts of food without feeling as hungry as they might when trying to lose weight through dieting alone.³

GLP-1 medications also affect the stomach and digestive system. For example, semaglutide slows down how quickly food leaves the stomach. This can help you feel full longer after eating. These medications also help the body release insulin when blood sugar is elevated; providing better blood sugar control.³

Why Does Appetite Decrease?

One of the most noticeable effects of GLP-1 medications is that you may simply not feel as hungry. Foods that you used to crave may not seem as appealing, and you may find yourself eating smaller portions or going longer between meals.

This decrease in appetite is one of the reasons GLP-1 medications can be so effective for weight loss. Research shows that these medications can reduce the amount of food people eat, which is an important part of how they help with weight loss.²,⁴

When you are eating much less than you did before, you may also be getting less protein, vitamins, minerals, fiber, and other nutrients your body needs. This is especially important because some people may already have low levels of certain nutrients before starting a weight-loss medication.²,⁵

Why Can Nutrient Intake Decrease?

When your appetite decreases, you naturally eat less food. While this can help with weight loss, it can also make it harder to get all the nutrients your body needs.

Some people taking GLP-1 medications also experience side effects such as nausea, vomiting, constipation, or diarrhea. These symptoms may make eating more difficult or cause you to avoid certain foods.⁵,⁶

When you are not very hungry, you may choose foods that are easiest to eat rather than foods that provide the most nutrition. If this continues over time, you may not get enough protein, fiber, vitamins, or minerals.

Researchers are beginning to pay more attention to possible nutrient deficiencies in people taking GLP-1 medications. Nutrients that may be a concern include vitamin D, iron, calcium, magnesium, vitamin B12, folate, and thiamine.⁵,⁷

The risk may be more important for people who remain on these medications for a long time or who lose weight quickly. Regular discussions with your healthcare provider and appropriate nutrition monitoring can help identify potential problems early.

The Relationship Between Weight Loss and Nutrition

When it comes to weight loss, the number on the scale is only part of the story. What you lose is also important.

Your body weight is made up of several things, including body fat, muscle and other lean tissue, bone, and water. GLP-1 medications generally help people lose more body fat than lean tissue, but some muscle and other lean tissue can also be lost during weight loss.⁸

Muscle is important for strength, balance, movement, physical activity, and overall health. Eating enough protein and staying physically active, especially by doing resistance exercises such as strength training, can help support muscle during weight loss.⁶,⁸

When your appetite is less, the foods you choose become even more important. Instead of focusing only on eating less, focus on getting the most nutrition from the food you do eat.

Choose foods that provide protein, vitamins, minerals, fiber, and other important nutrients. Staying hydrated is also important. Protein-rich foods can help support muscle while you are losing weight, and strength-training exercises can provide additional support for maintaining muscle.⁶,⁸

If you are taking a GLP-1 medication and find that you are struggling to eat enough, experiencing ongoing nausea or vomiting, feeling unusually tired, or having difficulty getting enough food or fluids, talk with your healthcare provider or registered dietitian.

GLP-1 medications can be powerful tools for weight management because they help reduce hunger, increase feelings of fullness, and make it easier to eat less. However, eating less food also means there can be fewer opportunities to get the nutrients your body needs.

Why Nutrition Matters More on GLP-1 Therapy

GLP-1 medications have changed the way many people approach weight management. Medications such as semaglutide and tirzepatide can reduce appetite, increase feelings of fullness, slow gastric emptying, and support significant weight loss. For many people, these effects are an important part of successful treatment.

When appetite decreases, eating less is often expected. However, eating substantially less can also make it harder to consume enough protein, vitamins, minerals, fiber, and other nutrients the body needs. During active weight loss, nutrition becomes especially important because the goal is not simply to make the number on the scale smaller. The goal is to support fat loss while preserving muscle, maintaining physical function, protecting bone health, and providing the nutrients needed for long-term health. Current clinical guidance specifically recommends monitoring nutritional intake during obesity medication treatment, with particular attention to protein and micronutrient intake.⁹

Reduced Food Intake: Eating Less Can Mean Getting Less Nutrition

One of the primary ways GLP-1 medications work is by reducing appetite and food intake. This is an important component of their effectiveness, but it can also create a nutritional challenge.

Research examining semaglutide, tirzepatide, and other GLP-1 medications has found substantial reductions in energy intake. A recent systematic review found that energy intake decreased by approximately 24% to 39% across studies of semaglutide or tirzepatide, although the amount varied between individuals and studies.¹⁰ Another recent meta-analysis found that GLP-1 receptor agonist treatment significantly reduced energy intake during standardized meal testing.¹¹

The problem is that the body does not need fewer vitamins and minerals simply because fewer calories are being consumed. Someone who previously ate 2,000 calories per day and now consumes 1,200–1,400 calories may have less tolerance to intake the same amount of protein, calcium, iron, vitamin B12, vitamin D, magnesium, and other nutrients due to side effects.

Instead of relying primarily on low-calorie foods that provide relatively little nutrition, people taking GLP-1 medications should generally prioritize nutrient-dense foods. Lean protein, vegetables, fruits, legumes, whole grains, dairy or fortified alternatives, seafood, eggs, nuts, and seeds can help provide more nutrients in smaller amounts of food.

For people experiencing nausea, early fullness, constipation, or other gastrointestinal symptoms, working with a registered dietitian nutritionist can be particularly helpful in developing an eating pattern that meets nutritional needs without overwhelming the appetite or digestive system.⁹

How Much Protein Do I Need on Semaglutide?

One of the most common questions people ask is: “How much protein do I need on semaglutide?” There is not one protein number that applies to everyone taking semaglutide or other GLP-1 options. Protein needs depend on body size, age, activity level, kidney function, muscle mass, overall calorie intake, and the rate of weight loss.  However, protein becomes particularly important during active weight reduction because inadequate protein intake can make it more difficult to preserve lean tissue.

Current obesity-care guidance suggests that approximately 1.2–1.6 g of protein per kilogram per day may be appropriate for many adults during active weight reduction, although the appropriate calculation method for individuals with obesity remains an area of clinical discussion.^9,12 Some guidance also recommends a minimum intake of approximately 60 g per day, with higher amounts often appropriate during active weight loss.⁹  Another important point is that protein intake should not be viewed in isolation. Eating more protein while consuming too few total calories, having a highly restrictive diet, or doing no resistance exercise may not fully protect muscle.

Make Protein a Priority

Because appetite may be limited, it can help to eat protein-rich foods first during meals.

Examples include:

• Eggs
• Greek yogurt
• Cottage cheese
• Fish and seafood
• Chicken or turkey
• Lean meats
• Tofu and tempeh
• Beans and lentils
• Edamame
• Milk or fortified dairy alternatives
• Protein-rich smoothies or shakes when appropriate

Smaller portions may be easier to tolerate than large meals. For some people, dividing protein across three meals and one or two small snacks can make it easier to reach their daily target.

Micronutrient Deficiencies: Why They Deserve Attention

Protein is not the only nutritional concern during GLP-1 therapy.  When overall food intake decreases, variety in food choices can decrease as well. Gastrointestinal symptoms such as nausea, vomiting, diarrhea, or food intolerance may further reduce intake. Delayed gastric emptying may also affect eating patterns and tolerance. These factors can contribute to nutritional deficiencies, particularly in people who already have an inadequate diet or a history of nutritional deficiencies. ¹³

Potential concerns involving nutrients such as:

• Iron
• Vitamin B12
• Vitamin D
• Calcium
• Magnesium
• Zinc
• Thiamine
• Folate
• Vitamin A
• Potassium

This does not mean that everyone taking a GLP-1 medication will develop a vitamin or mineral deficiency. The evidence regarding the frequency and clinical significance of these deficiencies is still being investigated. Some recent reviews emphasize that much of the available evidence comes from observational studies, nutritional assessments, or populations with additional risk factors.^13,14. The risk may be greater for people who have very low food intake, prolonged nausea or vomiting, poor baseline nutrition, gastrointestinal conditions, older age, or a history of bariatric surgery.¹³

This is one reason routine medical follow-up matters. Depending on an individual's health history and symptoms, a healthcare professional may recommend laboratory testing to identify nutritional deficiencies rather than assuming that supplementation is necessary. A multivitamin or targeted supplement may be appropriate for some individuals, but supplements should complement—not replace—a nutrient-dense eating pattern.

Muscle Loss on GLP-1: How Can You Prevent It? 

The phrase “Muscle Loss GLP-1” has become an important topic because significant weight loss can involve both fat mass and lean mass. This is not unique to GLP-1 medications. Whenever someone loses a substantial amount of weight, some lean tissue may be lost along with fat. However, preserving as much functional muscle as possible is an important part of healthy weight management.

In the STEP 1 trial of semaglutide, participants experienced substantial reductions in body weight. Body-composition analysis found that approximately 62% of the weight lost was fat mass and approximately 38% was lean body mass.¹⁵ Lean body mass includes muscle as well as other non-fat tissues, such a bone, so it should not be interpreted as meaning that 38% of the weight lost was muscle.

A 2026 systematic review and meta-analysis similarly found that lean mass represented approximately 35% of total weight lost with semaglutide in the included randomized trials. The review also found that resistance training was associated with a more favorable lean-mass profile.¹⁶

So, how can you help protect muscle?

1. Prioritize adequate protein

Protein provides amino acids needed to maintain and build muscle tissue. Adequate intake is particularly important when calorie intake is reduced.^9,12

2. Perform resistance training

Strength training is one of the most important tools for maintaining muscle during weight loss. Exercises can include weight machines, free weights, resistance bands, body-weight exercises, or other appropriately prescribed resistance activities. Research and expert guidance suggest that protein alone is not enough. Adequate protein works together with resistance exercise to support muscle preservation.^9,12

3. Avoid unnecessarily restrictive eating

The goal of GLP-1 therapy is not to eat as little as possible. Very low energy intake can make it difficult to meet protein and micronutrient needs and may increase nutritional risk. Nutrition should therefore focus on adequate intake while supporting the individual's weight-loss goals.¹²

4. Pay attention to strength and function

The scale cannot tell you everything about what is happening inside your body. Changes in strength, endurance, ability to climb stairs, ability to rise from a chair, and performance during exercise can provide useful information about physical function. Healthcare professionals may also use body-composition assessments when clinically appropriate.

Nutrition Matters Beyond the Scale

One of the biggest misconceptions about weight-loss treatment is that success can be measured entirely by pounds lost; long-term health is more complicated. Preserving muscle supports physical function and independence. Maintaining adequate protein and micronutrient intake supports normal physiological processes. Adequate calcium and vitamin D intake, combined with appropriate physical activity, can contribute to skeletal health. A balanced diet also provides fiber and a wide range of plant compounds associated with overall health.

Rapid or substantial weight loss can affect bone health as well as muscle mass, making nutritional intake and physical activity particularly important during treatment.^9,12 At the same time, GLP-1 medications can provide important metabolic benefits. The goal is not to discourage their use or to suggest that nutritional concerns outweigh their benefits. Rather, medication and nutrition should work together. Think of GLP-1 therapy as one part of a larger treatment plan.

The medication can help reduce appetite and support weight loss. Nutrition provides the raw materials needed to maintain the body during that process. Resistance exercise provides a stimulus to preserve muscle. Medical monitoring helps identify problems before they become significant.

Building a Nutrition-First GLP-1 Routine

A practical approach is to focus on a few consistent priorities:

Prioritize protein. Include a protein source at each meal and snack as tolerated.

Choose nutrient-dense foods. When portions are small, make those portions count by emphasizing foods rich in vitamins, minerals, protein, fiber, and other beneficial nutrients.

Don't ignore hydration. Reduced appetite can sometimes coincide with reduced fluid intake, particularly when gastrointestinal symptoms are present.

Include resistance exercise. Muscle preservation requires more than protein alone.

Monitor symptoms. Persistent nausea, vomiting, diarrhea, severe constipation, food intolerance, or an inability to eat enough should be discussed with a healthcare professional.

Monitor nutritional status when appropriate. Individual laboratory monitoring may be warranted based on medical history, dietary intake, symptoms, and risk factors.

Think long term. The objective is not simply to lose weight quickly. It is to develop an eating and activity pattern that supports health during weight loss and after weight loss.

The Bottom Line

GLP-1 medications can make it easier to eat less, but eating less does not automatically mean eating well.

As appetite decreases, every meal and snack may become more nutritionally important. Adequate protein can help support lean tissue, resistance training can help preserve muscle, and nutrient-dense foods can help provide the vitamins and minerals needed for health.

For people taking semaglutide or another GLP-1-based medication, nutrition should be considered part of the treatment, not an afterthought. The most successful approach is not necessarily the one that produces the fastest drop on the scale. It is an approach that supports appropriate weight loss while also protecting muscle, strength, nutritional status, bone health, and long-term well-being.

If you are taking a GLP-1 medication and struggling to eat enough, meet your protein needs, or determine whether you need nutritional supplements, consider discussing your individual needs with your physician or a registered dietitian.

What to Eat and What to Avoid While Taking a GLP-1 Medication

GLP-1 medications such as semaglutide and tirzepatide have become an important tool for managing obesity and improving metabolic health. These medications can help reduce appetite, increase feelings of fullness, slow gastric emptying, and improve blood glucose levels. ^17,18

Because GLP-1 medications can substantially change appetite and eating patterns, what you eat becomes especially important. When you are eating smaller portions, each meal should provide as much nutritional value as possible. The goal is not simply to eat less, it is to make sure the foods you do eat provide adequate protein, vitamins, minerals, fiber, healthy fats, and fluids.

A balanced eating pattern can also help minimize some of the gastrointestinal symptoms that may occur with GLP-1 medications, including nausea, bloating, constipation, diarrhea, and reflux.

Start With High-Protein Foods

Protein should be one of the priorities when taking a GLP-1 medication. Reduced appetite can make it challenging to consume enough protein, particularly when meals become significantly smaller. Adequate protein intake is important for maintaining muscle mass during weight loss.¹⁹

Good protein choices include:

• Chicken and turkey
• Fish and seafood
• Eggs
• Greek yogurt
• Cottage cheese
• Low-fat or reduced-fat cheese
• Lean beef or pork
• Tofu and tempeh
• Edamame
• Beans and lentils
• Protein-rich milk or fortified dairy alternatives
• Protein shakes or smoothies when appropriate

Try incorporating a source of protein into each meal. For example, breakfast might include eggs and Greek yogurt, lunch could include grilled chicken or fish, and dinner might feature salmon, tofu, or lean meat.

Protein does not have to come from animal products. Beans, lentils, soy foods, and other plant proteins can contribute substantially to daily protein intake.

Your individual protein needs depend on factors such as body size, age, physical activity, kidney function, and weight-loss goals. A registered dietitian can help determine an appropriate target.

Don't Forget Fruits and Vegetables

When appetite is reduced, vegetables and fruits can help provide important vitamins, minerals, antioxidants, and fiber without requiring large portions.

Good vegetable choices include:

• Leafy greens
• Broccoli
• Cauliflower
• Bell peppers
• Carrots
• Green beans
• Zucchini
• Tomatoes
• Brussels sprout
• Squash

Fruits can also be part of a healthy GLP-1 eating pattern. Berries, apples, oranges, kiwi, melon, peaches, and pears provide nutrients and, depending on the fruit, varying amounts of fiber.

If you experience significant bloating or digestive discomfort, however, you may find that some raw vegetables or larger amounts of certain fruits are harder to tolerate. In that situation, cooked vegetables, peeled fruits, or smaller portions may be easier to digest. Rather than eliminating fruits and vegetables, experiment with portion size, preparation method, and individual tolerance.

Choose Fiber-Rich Carbohydrates

Carbohydrates do not need to be eliminated while taking a GLP-1 medication. In fact, high-quality carbohydrates can provide fiber, vitamins, minerals, and energy.

Examples of fiber-rich carbohydrates include:

• Oatmeal
• Quinoa
• Brown rice
• Barley
• Whole-grain bread
• Whole-grain pasta
• Beans
• Lentils
• Sweet potatoes

Fiber can be particularly helpful for maintaining regular bowel movements, especially because constipation is a commonly reported gastrointestinal issue with GLP-1 medications.²⁰ However, there is caution: increase fiber gradually.

If you suddenly increase your fiber intake while your fluid intake remains low, constipation, bloating, or abdominal discomfort may become worse. Gradually increasing fiber while drinking adequate fluids is generally a better strategy.

Include Healthy Fats—But Watch Portion Sizes

Healthy fats can be part of a nutritious GLP-1 meal plan. They provide essential fatty acids and help the body absorb fat-soluble vitamins.

Good choices include:

• Avocado
• Olive oil
• Nuts
• Seeds
• Natural nut butters
• Fatty fish such as salmon

Because GLP-1 medications slow gastric emptying, very large amounts of high-fat food may be difficult for some people to tolerate. Fat also contains more calories per gram than protein or carbohydrates, so portion size matters when weight loss is a goal.

Instead of eating a large, high-fat meal, try incorporating smaller amounts of healthy fats throughout the day.

For example, add a small amount of avocado to a meal, sprinkle nuts or seeds over yogurt, or use a modest amount of olive oil when preparing vegetables.

Hydration Matters

Drinking enough fluid is an important part of nutrition while taking a GLP-1 medication. Reduced appetite can sometimes be accompanied by reduced fluid intake. In addition, vomiting or diarrhea can increase fluid losses. Adequate hydration is also particularly important when increasing dietary fiber.

Water is an excellent primary choice. Other options can include unsweetened tea, sparkling water if tolerated, broth, and other low- or no-sugar beverages. Rather than drinking a large amount at once, some people find it easier to sip fluids throughout the day.

If nausea is an issue, drinking fluids slowly and choosing beverages that are well tolerated may be easier than consuming a large glass quickly. People with medical conditions that require fluid restriction should follow their healthcare provider's recommendations rather than general hydration advice.

What Foods Should You Limit?

There is no universal list of foods that every person taking a GLP-1 medication must completely avoid. However, certain foods are more likely to worsen gastrointestinal symptoms or make it difficult to meet nutritional goals.

Very high-fat or greasy foods

Fried foods, heavily buttered foods, creamy sauces, fatty cuts of meat, and other high-fat meals may cause or worsen nausea, reflux, bloating, or abdominal discomfort in some people. If these foods bother you, choose grilled, baked, roasted, or steamed alternatives.

Large meals

One of the simplest changes you can make is to reduce meal size. Because GLP-1 medications can slow gastric emptying and increase feelings of fullness, large meals may leave you feeling overly full or uncomfortable.17,18 Try eating smaller meals and stopping when you feel comfortably satisfied.

Highly processed and sugary foods

Candy, pastries, sugar-sweetened beverages, chips, and other highly processed foods can provide substantial calories without supplying much protein, fiber, vitamins, or minerals. These foods do not necessarily have to be completely eliminated, but they should generally not displace nutrient-dense foods—especially when appetite is limited.

Alcohol

Alcohol may worsen gastrointestinal symptoms for some individuals and can add calories without providing substantial nutritional value. It may also interact with other medications or be inappropriate for people with certain medical conditions. Discuss alcohol use with your healthcare provider, particularly if you are experiencing nausea, vomiting, reflux, or other digestive symptoms.

Foods to Limit When You Have Nausea

If nausea occurs, temporarily choosing simpler and lower-fat foods may help.

Options that some people tolerate better include:

• Crackers or toast
• Rice
• Oatmeal
• Bananas
• Applesauce
• Potatoes
• Broth-based soups
• Eggs
• Low-fat yogurt
• Lean chicken
• Small portions of cooked vegetables

You may want to temporarily limit greasy or fried foods, very spicy foods, large portions, strong odors, and very rich meals if they trigger symptoms. Eat slowly and avoid forcing yourself to finish a meal when you are already comfortably full. Persistent or severe nausea, repeated vomiting, inability to keep fluids down, or significant abdominal pain should be discussed promptly with your healthcare provider.

What About Bloating, Constipation, or Diarrhea?

Digestive symptoms can vary considerably from person to person. For constipation, adequate fluids, gradual increases in fiber, fruits and vegetables, and regular physical activity may help.²⁰

If diarrhea occurs, temporarily choosing easily tolerated foods and maintaining hydration may be helpful. Very greasy foods, excessive amounts of sugar alcohols, and large portions of high-fiber foods may worsen symptoms for some people. The key is to identify your personal triggers rather than unnecessarily eliminating entire food groups.

Build Your Plate Around Nutrition

A simple approach is to think about your meal in this order:

1. Protein: Start with chicken, fish, eggs, Greek yogurt, tofu, beans, or another protein source.
2. Produce: Add vegetables and/or fruit based on what you tolerate.
3. High-quality carbohydrates: Include whole grains, beans, or another fiber-rich carbohydrate.
4. Healthy fat: Add a modest amount of avocado, nuts, seeds, olive oil, or fatty fish.
5. Fluids: Drink consistently throughout the day.

Because appetite may be significantly reduced, you may not always be able to eat every component at every meal. Focus on the overall 

The Bottom Line

Taking a GLP-1 medication does not mean you need to follow an extremely restrictive diet. Instead, it is an opportunity to make the foods you eat more nutrient-dense. Prioritize protein to support muscle, fruits and vegetables for vitamins, minerals, antioxidants, and fiber, high-quality carbohydrates for energy and digestive health, healthy fats in appropriate portions, and adequate fluids for hydration.

At the same time, pay attention to how your body responds. Large meals, greasy foods, very high-fat meals, excessive alcohol, and certain spicy or highly processed foods may worsen gastrointestinal symptoms for some people. Most importantly, listen to your body's signals. Reduced appetite is an intended effect of GLP-1 therapy, but the goal should not be to eat as little as possible. The goal is to nourish your body while supporting healthy, sustainable weight management.

If you are having difficulty eating enough protein or getting adequate nutrition because of nausea, early fullness, or other digestive symptoms, a registered dietitian nutritionist can help create an individualized eating plan that works alongside your medication.

Vitamins and Minerals to Consider When Taking a GLP-1 Medication

GLP-1 medications have become an important tool for managing obesity and improving metabolic health. Medications such as semaglutide and tirzepatide can decrease appetite, increase feelings of fullness, and reduce overall intake. These effects can be helpful for weight management, but eating less can also make it more difficult to meet daily vitamin and mineral needs.

Recent research suggests that GLP-1 receptor agonist therapy may be associated with nutritional deficiencies, particularly when lack of appetite reduces food intake. Potential concerns include vitamin D, iron, calcium, magnesium, thiamin, vitamin B12, folate, and other micronutrients. However, much of the available evidence is observational, so it is not yet possible to say that GLP-1 medications directly cause deficiencies in every patient.^21˒22 For people taking semaglutide or another GLP-1 medication, individualized nutrition care can help determine whether supplementation is appropriate.

Why Can GLP-1 Medications Affect Nutrient Intake?

GLP-1 medications can reduce hunger and the amount of food consumed at meals. They can also slow gastric emptying, and gastrointestinal symptoms such as nausea, vomiting, diarrhea, constipation, and early fullness can affect dietary intake and food variety.

When someone eats substantially less food because they are lacking an appetite, there may be fewer opportunities to consume nutrient-rich foods. For example, someone who previously ate three full meals may begin eating much smaller portions and may avoid certain foods because they cause nausea or feel too heavy.

A 2026 narrative review found that vitamin D deficiency was a commonly reported abnormality among GLP-1 receptor agonist users, while iron depletion and inadequate calcium and iron intake were also observed. The researchers emphasized that current evidence is primarily observational and that individualized nutritional assessment is appropriate, particularly for people at increased risk.²¹

1. Iron

What does iron do?

Iron is essential for producing hemoglobin, the protein in red blood cells responsible for carrying oxygen throughout the body. Iron also supports muscle function, cellular energy production, and normal neurological development.²³

Why is iron important with GLP-1 medications?

People taking GLP-1 medications may consume smaller portions and less dietary variety. If iron-rich foods such as meat, seafood, beans, lentils, and fortified grains are eaten less frequently, iron intake can decline.  Iron status may be especially important for menstruating women, who have higher iron requirements.

Signs of iron deficiency

Possible symptoms include:

• Fatigue
• Weakness
• Headaches
• Dizziness
• Pale skin
• Shortness of breath
• Reduced exercise tolerance
• Difficulty concentrating
• Brittle nails

Food sources

Good sources include lean beef, poultry, seafood, beans, lentils, spinach, peas, nuts, seeds, and iron-fortified cereals. Vitamin C-rich foods can help improve absorption of nonheme iron from plant foods.

Should you take an iron supplement?

Iron supplementation is best guided by dietary intake and laboratory testing, such as a complete blood count and ferritin when clinically indicated. Unnecessary iron supplementation can cause gastrointestinal side effects and excessive intake can be harmful.

 Start the Quiz 

2. Vitamin B12

What does vitamin B12 do?

Vitamin B12 supports DNA synthesis, healthy red blood cell production, and normal development and function of the nervous system.²⁴

Why is B12 important with GLP-1 medications?

When appetite is reduced, people may eat less meat, fish, eggs, and dairy products, the primary natural dietary sources of vitamin B12.  People following vegetarian or vegan diets may also require special attention to B12 intake.

Signs of B12 deficiency

Symptoms may include:

• Fatigue
• Weakness
• Pale skin
• Sore or swollen tongue
• Numbness or tingling
• Balance problems
• Cognitive changes

Neurological symptoms deserve prompt medical attention because prolonged B12 deficiency can cause permanent neurological issues.

Food sources

Vitamin B12 is found naturally in:

• Fish
• Meat
• Poultry
• Eggs
• Milk
• Yogurt
• Cheese

Fortified foods can provide B12 for people who consume few or no animal products.

Supplementation

The adult RDA is 2.4 mcg per day.²⁴ A standard multivitamin containing B12 may help cover dietary gaps, especially for vegetarians, while individuals with documented deficiency or absorption problems may require a higher-dose supplement under medical supervision.

3. Vitamin D

What does vitamin D do?

Vitamin D helps the body absorb calcium and maintain healthy bones. It also plays roles in muscle and neuromuscular function and immune health.²⁵

Why is vitamin D important with GLP-1 therapy?

Reduced food intake can mean fewer servings of vitamin D-fortified foods and fatty fish. Vitamin D is particularly relevant during weight loss because maintaining adequate vitamin D and calcium intake supports skeletal health.

Signs of deficiency

Vitamin D deficiency may contribute to:

• Bone pain
• Muscle weakness
• Reduced bone mineralization
• Increased risk of fragile bones

Food sources

Food sources include:

• Salmon
• Tuna
• Egg yolks
• Fortified milk
• Fortified plant-based beverages
• Fortified cereals

Supplementation

The RDA is 600 IU (15 mcg) daily for adults through age 70 and 800 IU (20 mcg) after age 70.²⁵ Higher doses may be appropriate for documented deficiency, but should be individualized. A 25-hydroxyvitamin D blood test can help determine vitamin D status when testing is clinically appropriate.

4. Calcium

What does calcium do?

Calcium is essential for bones and teeth, but it also supports muscle contraction, nerve transmission, blood clotting, and other physiological processes.²⁶

Why is calcium important with GLP-1 medications?

A reduced appetite may result in fewer servings of dairy products or calcium-fortified alternatives. Calcium is particularly important during weight loss because inadequate intake can compromise long-term bone health.

Signs of inadequate calcium

Long-term inadequate intake can contribute to reduced bone strength and osteoporosis. Significant abnormalities in blood calcium can cause muscle cramps, tingling, and muscle spasms.

Food sources

Excellent sources include:

• Milk
• Yogurt
• Cheese
• Calcium-fortified plant beverages
• Calcium-fortified orange juice
• Calcium-set tofu
• Sardines with bones
• Canned salmon with bones
• Kale and other vegetables

Supplementation

Most adults ages 19–50 need approximately 1,000 mg of calcium daily. Women ages 51–70 generally need 1,200 mg, and adults over 70 need 1,200 mg.²⁶

 Start the Quiz 

5. Folate

What does folate do?

Folate, or vitamin B9, is required for DNA synthesis, cell division, amino acid metabolism, and normal red blood cell production.²⁷

Why is folate important?

Reduced intake of vegetables, beans, legumes, fruits, and fortified grains can reduce folate intake.

Signs of folate deficiency

Deficiency may cause megaloblastic anemia and symptoms such as:

• Fatigue
• Weakness
• Difficulty concentrating
• Headaches
• Irritability
• Shortness of breath
• Sore tongue

Food sources

Good sources include:

• Spinach
• Asparagus
• Brussels sprouts
• Beans
• Peas
• Citrus fruits
• Avocados
• Eggs
• Fortified grains and cereals

Supplementation

The adult RDA is 400 mcg dietary folate equivalents (DFE) daily.²⁷ Individuals who could become pregnant have additional folic acid recommendations.

6. Magnesium

What does magnesium do?

Magnesium is involved in hundreds of biochemical reactions. It supports energy metabolism, protein synthesis, muscle and nerve function, blood glucose regulation, blood pressure regulation, and normal heart rhythm.²⁸

Why is magnesium important with GLP-1 therapy?

If someone is eating fewer nuts, seeds, whole grains, beans, and vegetables, magnesium intake may decline.

Signs of deficiency

Early symptoms can include:

• Loss of appetite
• Nausea
• Vomiting
• Fatigue
• Weakness

More severe deficiency can cause:

• Muscle cramps
• Numbness
• Tingling
• Abnormal heart rhythms
• Seizures

Food sources

Good sources include:

• Pumpkin seeds
• Chia seeds
• Almonds
• Cashews
• Spinach
• Black beans
• Edamame
• Whole grains

Supplementation

Adult magnesium requirements generally range from 310–320 mg for women and 400–420 mg for men, depending on age.²⁸ Supplementation should be individualized because excessive supplemental magnesium can cause diarrhea and gastrointestinal discomfort.

7. Thiamin

What does thiamin do?

Thiamin, or vitamin B1, plays an essential role in energy metabolism and supports normal cellular growth and function.²⁹

Why is thiamin important with GLP-1 medications?

Thiamin deserves particular attention when food intake becomes extremely low or when persistent vomiting occurs.

The body stores relatively little thiamin, so prolonged inadequate intake can become clinically important.

Signs of deficiency

Possible symptoms include:

• Loss of appetite
• Weight loss
• Weakness
• Confusion
• Memory problems
• Numbness or tingling
• Poor reflexes
• Cardiovascular problems

Severe deficiency can result in beriberi or Wernicke-Korsakoff syndrome.

Food sources

Good sources include:

• Pork
• Fish
• Whole grains
• Fortified cereals
• Fortified breads
• Beans
• Nuts
• Seeds

Supplementation

The adult RDA is 1.2 mg for men and 1.1 mg for women.²⁹ A standard multivitamin usually provides thiamin. Individuals experiencing persistent vomiting or extremely limited intake should contact their healthcare provider rather than relying solely on over-the-counter supplementation.

8. Vitamin A

What does vitamin A do?

Vitamin A supports:

• Vision
• Immune function
• Cell growth
• Reproduction
• Tissue maintenance
• Normal development

It is also essential for the function of the retina.³⁰

Why is vitamin A important with GLP-1 medications?

If overall food intake and dietary variety decline, intake of colorful vegetables and other vitamin A sources may decrease.

Signs of deficiency

One classic sign is difficulty seeing in low-light conditions or night blindness. More severe deficiency can affect immune function and eye health.

Food sources

Preformed vitamin A is found in:

• Eggs
• Dairy products
• Some fish

Provitamin A carotenoids are found in:

• Sweet potatoes
• Carrots
• Spinach
• Kale
• Winter squash
• Other orange, yellow, and dark green vegetables

Supplementation

Adult recommendations are approximately 900 mcg RAE daily for men and 700 mcg RAE for women.³⁰ Vitamin A supplements should be used cautiously because excessive preformed vitamin A can cause toxicity.

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References

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22. Kerlikowsky F, Krämer K, Eggersdorfer M, Hahn A. GLP-1 receptor agonists—good for body weight, bad for micronutrient status? Curr Dev Nutr. 2025;9(11):107587. (PubMed)

    National Institutes of Health, Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

23. National Institutes of Health, Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

24. National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

25. National Institutes of Health, Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

26. National Institutes of Health, Office of Dietary Supplements. Folate: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

27. National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

28. National Institutes of Health, Office of Dietary Supplements. Thiamin: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

29. National Institutes of Health, Office of Dietary Supplements. Vitamin A and Carotenoids: Fact Sheet for Health Professionals. (Office of Dietary Supplements)

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