GLP-1 Medications: Understanding Nutritional Gaps & How to Support Your Nutrition

GLP-1 receptor agonist medicines are increasingly used in the management of type 2 diabetes and, for certain medicines and patients, weight management.

These medicines can reduce appetite and food intake. As a result, people taking GLP-1 medicines may find that they eat smaller portions or consume less food overall. Emerging research suggests that this can make it more difficult for some people to achieve recommended intakes of certain nutrients.¹˒²

This does not mean that everyone taking a GLP-1 medicine will develop a nutritional deficiency. However, maintaining a balanced, nutrient-dense diet remains important, particularly when overall food intake is reduced.

Why Can Nutrient Intake Be Lower When Taking GLP-1 Medicines?

1. Reduced Food Intake

GLP-1 medicines can reduce appetite and overall energy intake. When someone is eating considerably less food, careful food choices can become increasingly important for maintaining adequate nutritional intake.

A 2025 multidisciplinary advisory on nutrition during GLP-1 therapy identified reduced calorie intake and the potential for inadequate nutrient intake among the nutritional considerations associated with treatment.¹

2. Gastrointestinal Side Effects

Gastrointestinal symptoms can occur with GLP-1 medicines. These may include nausea, vomiting, diarrhoea, constipation and feelings of fullness, depending on the individual medicine.

These symptoms may sometimes make it more difficult to maintain normal food and fluid intake. A 2025 BMJ article highlighted the importance of assessing nutritional status in people using GLP-1 medicines where there is a risk of inadequate nutrition.²

If side effects are persistent, severe or are making it difficult to eat or drink normally, speak to your doctor or pharmacist rather than changing or stopping prescribed treatment yourself.

What Does the Research Say About Nutrient Intake?

Research in this area is still developing.

A 2025 cross-sectional study examined the dietary intake of 69 people who had been using a GLP-1 receptor agonist for at least one month. Average dietary intakes were below the study's reference values for several nutrients, including:

Fibre
Calcium
Iron
Magnesium
Potassium
Choline
Vitamin A
Vitamin C
Vitamin D
Vitamin E³

Importantly, this was a relatively small observational study. It demonstrates that inadequate dietary intake can occur in people taking GLP-1 medicines, but it does not establish that the medicines themselves directly cause depletion or deficiency of these nutrients.

A larger 2026 review discussed by Harvard Health also reported nutritional deficiencies among some GLP-1 medicine users, while highlighting the need for attention to nutritional status during treatment.⁴

Important Nutrients to Consider

Calcium & Vitamin D

Calcium and vitamin D are important nutrients, particularly when considering normal bone health.

Calcium is needed for the maintenance of normal bones.
Vitamin D contributes to the maintenance of normal bones.
Vitamin D contributes to normal absorption and utilisation of calcium and phosphorus.
Vitamin D contributes to normal blood calcium levels.⁵

Food sources of calcium can include milk, yoghurt, cheese and calcium-fortified alternatives.

Vitamin D is naturally present in relatively few foods. Sources include oily fish, egg yolks and appropriately fortified foods.

Iron

Iron intake may require attention where overall food intake or consumption of iron-containing foods is reduced.

Iron contributes to normal energy-yielding metabolism.
Iron contributes to the normal formation of red blood cells and haemoglobin.
Iron contributes to normal oxygen transport in the body.
Iron contributes to the reduction of tiredness and fatigue.⁵

Sources include meat, fish, legumes, fortified cereals, nuts, seeds and some green vegetables.

Iron supplements should not automatically be taken simply because someone is using a GLP-1 medicine. Speak to a healthcare professional if iron deficiency is suspected.

Magnesium

The 2025 dietary study found average magnesium intake below the relevant reference level among participants.³

Magnesium contributes to normal energy-yielding metabolism.
Magnesium contributes to normal muscle function.
Magnesium contributes to normal functioning of the nervous system.
Magnesium contributes to the reduction of tiredness and fatigue.
Magnesium contributes to the maintenance of normal bones.⁵

Food sources include nuts, seeds, wholegrains, legumes and green leafy vegetables.

B Vitamins

B vitamins perform a range of normal functions in the body. It is important not to group all B vitamins under the same health claim because authorised claims differ between individual vitamins.

For example:

Vitamin B12 contributes to normal energy-yielding metabolism.
Vitamin B12 contributes to normal functioning of the nervous system.
Vitamin B12 contributes to the reduction of tiredness and fatigue.
Thiamine contributes to normal energy-yielding metabolism.⁵

The 2025 dietary study did not find inadequate average intake of all B vitamins, so it would be misleading to state that B-vitamin deficiency is universal or expected in GLP-1 users.³

Vitamins A, C & E

The 2025 study reported average dietary intakes below the relevant reference values for vitamins A, C and E in its study population.³

Vitamin A contributes to the maintenance of normal skin.
Vitamin A contributes to the normal function of the immune system.
Vitamin C contributes to the normal function of the immune system.
Vitamin C contributes to the protection of cells from oxidative stress.
Vitamin C contributes to the reduction of tiredness and fatigue.
Vitamin E contributes to the protection of cells from oxidative stress.⁵

Fruit, vegetables, nuts, seeds and other nutrient-dense foods can contribute to the intake of these vitamins.

How Can You Support Good Nutrition While Taking a GLP-1 Medicine?

Prioritise Nutrient-Dense Foods

When appetite is reduced, choosing foods that provide protein, vitamins, minerals and other important nutrients can help maximise the nutritional value of the food you are able to eat.

Depending on individual dietary requirements, examples can include:

Eggs
Fish
Lean meat or poultry
Greek or natural yoghurt
Beans and lentils
Tofu
Fruit and vegetables
Nuts and seeds
Wholegrains
Fortified dairy alternatives

Your individual requirements may differ, particularly if you have diabetes, kidney disease, gastrointestinal conditions or another medical condition requiring dietary management.

Include an Appropriate Source of Protein

Adequate protein intake is an important consideration during weight loss. The 2025 multidisciplinary GLP-1 nutrition advisory specifically identifies preservation of lean mass as an important part of nutritional and lifestyle management during GLP-1 therapy.¹

Rather than applying the same protein target to everybody, requirements should be individualised according to factors such as body size, age, activity, overall health and medical conditions.

Include Fibre as Part of a Balanced Diet

Foods containing fibre include:

Wholegrains
Oats
Beans and lentils
Fruit
Vegetables
Nuts and seeds

If your usual fibre intake is low, increasing it gradually may be more comfortable. Adequate fluid intake is also important.

People experiencing persistent gastrointestinal symptoms while taking GLP-1 medicines should discuss these with their healthcare professional.

What About Vitamin and Mineral Supplements?

A food supplement should complement rather than replace a varied, balanced diet and healthy lifestyle.

Taking a GLP-1 medicine does not automatically mean that you need a multivitamin, iron supplement or other nutritional supplement.

The most appropriate approach depends on your diet, symptoms, medical history, other medicines and, where clinically appropriate, blood-test results.

If reduced appetite is making it difficult to maintain a balanced diet, or if you are concerned about a particular nutrient deficiency, speak to your doctor, pharmacist or dietitian.

Can Supplements Treat GLP-1 Side Effects?

Food supplements should not be regarded as treatments for the adverse effects of GLP-1 medicines.

Under Irish and EU food law, food supplements cannot be presented as preventing, treating or curing a human disease. Health claims made for foods and food supplements must comply with the applicable EU-authorised health-claims legislation.⁵˒⁶

If you experience troublesome or persistent side effects from a GLP-1 medicine, contact your doctor or pharmacist for advice.

Final Thoughts

GLP-1 medicines can substantially reduce appetite and food intake. Emerging evidence suggests that some people using these medicines may have dietary intakes below recommended levels for certain nutrients.¹˒³

This should not be interpreted as evidence that every person taking a GLP-1 medicine will develop a nutritional deficiency or that GLP-1 medicines directly “deplete” vitamins and minerals.

A varied, balanced and nutrient-dense diet remains the foundation of good nutrition. Where food intake is significantly reduced, a healthcare professional can help assess whether dietary changes, nutritional monitoring or supplementation are appropriate.

If you are taking a GLP-1 medicine, do not stop or change your prescribed treatment without speaking to your prescriber.

Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle.

Sources

Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional priorities to support GLP-1 therapy for obesity: a joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. American Journal of Clinical Nutrition. 2025;122(1):344–367. DOI: 10.1016/j.ajcnut.2025.04.023.
Fallows E. Malnutrition with use of GLP-1 agonists is an underestimated real world harm. BMJ. 2025;390. DOI: 10.1136/bmj.r1512.
Johnson B, Milstead M, Thomas O, et al. Investigating nutrient intake during use of glucagon-like peptide-1 receptor agonist: a cross-sectional study. Frontiers in Nutrition. 2025;12:1566498. DOI: 10.3389/fnut.2025.1566498.
Harvard Health Publishing. Study: Taking GLP-1 drugs may increase risk of key nutrient deficiencies. Published 18 March 2026.
Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods, as amended.
Regulation (EC) No 1924/2006 on nutrition and health claims made on foods.