What Supplements Should You Take on a GLP-1 Medicine?

On a GLP-1 medicine the supplements worth considering are the ones that stand in for what a smaller appetite no longer supplies: protein, fibre, electrolytes on sick days and magnesium, with vitamin D, vitamin B12, iron and folate as the nutrients to ask your GP to test rather than guess at. Tirzepatide (Mounjaro), semaglutide (Wegovy, Ozempic) and liraglutide (Saxenda) cut food intake by about a quarter in trials, and a quarter less food carries a quarter less of everything in it unless the plate changes.¹ Nothing here replaces the medicine or adds to its effect; the question is nutritional, and food answers most of it.

• Protein first: the nutrient a small appetite drops furthest, and the one that protects muscle
• Fibre: 30 g a day is the UK target; most people on the medicine sit under 20 g
• Test, don't guess: vitamin D, B12, ferritin and folate after months of eating less

Why does a GLP-1 medicine change what you need from supplements?

The medicines copy the gut hormone GLP-1, hold its receptors stimulated all week, slow stomach emptying and quieten appetite; in the trial that measured it, people on semaglutide ate about 24% less at a free-choice meal than people on placebo, without being told to.¹ Nobody plans to eat a quarter less protein, fibre or magnesium, but that is what happens when every portion shrinks and the bulky foods go first. Weight that comes off quickly includes muscle unless protein and resistance training protect it: in the tirzepatide body-composition sub-study about a quarter of the weight lost was lean mass.² What GLP-1 is explains the hormone; this page is one chapter of our guide to living well on Mounjaro.

Do you need a protein supplement on a GLP-1 medicine?

Often, in the first months, because protein is the hardest target to hit on a small plate. The UK reference nutrient intake for adults is 0.75 g per kilogram of body weight a day, about 55 g for a man and 45 g for a woman.⁴ During deliberate weight loss the trials that protected muscle best used 1.2 to 1.6 g per kilogram, in portions of 25 to 30 g at each meal.⁵ Food first: eggs, Greek yoghurt, cottage cheese, chicken, fish, tofu, lentils and milk. A shake fits the meal you cannot face: 20 g of protein in a glass goes down on a nauseous morning when 100 g of chicken will not. Wellgard's Vegan Protein provides 20.28 g of protein in a 26 g serving, and protein contributes to growth in muscle mass and to the maintenance of muscle mass. How much protein you need on Mounjaro sets the target by body weight.

Should you take a fibre supplement on a GLP-1 medicine?

If food cannot get you to 30 g a day, yes, slowly. The UK target is 30 g and the average adult manages 18 to 20 g; a smaller appetite drops it further, because vegetables, pulses and wholegrains leave the plate first.^{4, 6} Fibre keeps stools soft when the gut is moving slowly, which is why constipation affected about one person in six in the tirzepatide trials, and it extends fullness between small meals.³ Oats, chia, pulses, pears and seeded bread come first; a supplement is a top-up, not a swap, and pace matters more than type: add about 5 g every few days with 1.5 to 2 litres of fluid, because fibre without water makes constipation worse. Psyllium husk is the best-studied option. Wellgard's High Fibre Gummies carry 4 g of soluble fibre, mostly inulin, in a three-gummy serving. How much fibre you need on Mounjaro has the food list and the build-up plan.

Do you need electrolytes on a GLP-1 medicine?

On ordinary days, no: food and water supply the sodium, potassium and magnesium your body runs on. The days that change the answer are the ones with vomiting or diarrhoea, which lose fluid and salts together, hot weather, or a day when intake is so low that the salts went missing with the calories. The UK reference intake for potassium is 3,500 mg a day, which a 900 kcal day does not reach.⁴ A banana and a glass of milk for potassium, a pinch of salt in soup, nuts and seeds for magnesium fix most of it; an electrolyte sachet is the sick-day tool and never a reason to drink less water. Wellgard's ElectroMight Daily Electrolytes provides 300 mg of sodium, 200 mg of potassium and 62.5 mg of magnesium in a 5 g sachet, and magnesium contributes to electrolyte balance. Ask your pharmacist first if you take a blood-pressure medicine or have a kidney condition. Headaches on Mounjaro covers how much water to drink.

Is magnesium worth taking on a GLP-1 medicine?

The UK reference intake is 300 mg a day for men and 270 mg for women, and magnesium lives in nuts, seeds, wholegrains, pulses and leafy greens, exactly the foods a narrowed diet squeezes out.⁷ There is no trial of magnesium in people taking a GLP-1 medicine, so the case rests on intake, not on the drug. Magnesium contributes to the reduction of tiredness and fatigue and to normal muscle function; if your diet has narrowed, a supplement covers the intake while the food is not going in. Wellgard's Mag 1200 Magnesium Glycinate provides 240 mg of elemental magnesium in two capsules; do not exceed the stated dose, and more than your body needs can have a laxative effect, worth knowing on a medicine that already causes diarrhoea.³

Which vitamins should you ask your GP to test?

Vitamin D, vitamin B12, ferritin and folate, with a full blood count, after a few months of eating less, or sooner if you are tired, breathless or shedding hair. Test rather than guess, because each shortfall looks exactly like the medicine's own tiredness.

• Vitamin D. The NHS advises every adult to consider 10 micrograms a day from October to March, and not to exceed 100 micrograms a day from supplements.⁸ Wellgard's Vitamin D Capsules provide 75 micrograms (3,000 IU) per capsule, and vitamin D contributes to the maintenance of normal bones and to normal muscle function.
• Vitamin B12. The reference intake is 1.5 micrograms a day from animal or fortified foods, so it matters if meat, fish, eggs and dairy have dropped out, if you are vegan, or if you take metformin, which lowers B12 over years of use.^{4, 9} Wellgard's Vitamin B12 Capsules provide 500 micrograms of methylcobalamin per capsule, and vitamin B12 contributes to the reduction of tiredness and fatigue and to normal red blood cell formation.
• Iron and folate. Iron is the one never to take just in case: unneeded iron causes constipation and stomach upset, and overload is a real risk, so a ferritin test decides it.¹⁰ Folate comes from leafy greens and pulses.

Why am I so tired on Mounjaro names the six tests to ask for, and the sub-hub which vitamins to take on Mounjaro goes nutrient by nutrient, including calcium and zinc.

Is there a best all-in-one supplement for a GLP-1 medicine?

No single product covers the list, because the list is mostly food: protein by the hundred grams and fibre by the tens of grams do not fit in a capsule, and a multivitamin supplies neither. The real shape of a "GLP-1 stack" is a protein powder for the meals you cannot face, a fibre source if food falls short, an electrolyte sachet for sick days, magnesium if your diet has narrowed, vitamin D in winter, and B12 or iron when a test says so. Products sold as GLP-1 boosters are a different category, and do GLP-1 supplements work goes through their ingredients one by one.

What should you not take, or space from a GLP-1 medicine?

No vitamin or mineral is banned because of the medicine, but the slowed stomach changes timing: anything you swallow can be absorbed later or less completely, and the NHS advice is to tell your prescriber about every supplement and herbal remedy you take.¹¹ Four rules. Keep psyllium and other bulk fibres two hours away from anything else you swallow, because they can slow its absorption. Take iron and calcium at different times from each other. Do not add iron, vitamin A above the reference intake or high-dose biotin without a reason, and tell whoever takes your blood about any biotin supplement, because it can distort thyroid and other test results. And treat berberine as a prescriber conversation, not a GLP-1 add-on: berberine with or after Mounjaro explains why. Report side effects through the MHRA Yellow Card scheme; GLP-1 side effects: what is common and what helps puts the food fixes first.

Frequently asked questions

What supplements should you not take while on a GLP-1 medicine?

None is forbidden, but iron without a test, vitamin A above the reference intake, high-dose biotin before a blood test, and anything claiming to copy the medicine are the ones to leave out. Tell your prescriber what you take.¹¹

Which GLP-1 companion supplement is the best?

The one that fills your own gap: for most people protein, then fibre, then an electrolyte sachet kept for sick days. A test decides the vitamins.

Does magnesium make you hungry?

No trial shows that. Magnesium contributes to normal muscle function and to the reduction of tiredness and fatigue; it has no measured effect on appetite in either direction.

Is the advice the same on Wegovy, Ozempic and Saxenda?

Yes. Semaglutide and liraglutide reduce intake and slow the stomach the same way, so the nutrition is the same. What the GLP-1 diet is covers the eating pattern itself.

Sources

1. Blundell J, et al. Effects of once-weekly semaglutide on appetite, energy intake, control of eating, food preference and body weight in subjects with obesity. Diabetes, Obesity and Metabolism, 2017. PubMed 28266779.
2. Look M, et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight. Diabetes, Obesity and Metabolism, 2025. PubMed 39996356.
3. Jastreboff AM, et al. Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine, 2022. PubMed 35658024.
4. Public Health England. Government dietary recommendations: energy and nutrients, 2016. assets.publishing.service.gov.uk.
5. Leidy HJ, et al. The role of protein in weight loss and maintenance. American Journal of Clinical Nutrition, 2015. PubMed 25926512.
6. NHS. How to get more fibre into your diet. nhs.uk.
7. NHS. Vitamins and minerals: others, including magnesium. nhs.uk.
8. NHS. Vitamin D. nhs.uk.
9. de Jager J, et al. Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial. BMJ, 2010. PubMed 20488910.
10. NHS. Iron deficiency anaemia. nhs.uk.
11. NHS. Tirzepatide. nhs.uk/medicines/tirzepatide.

This article is general information, not medical advice. Mounjaro, Wegovy, Ozempic and Saxenda are prescription medicines: follow your prescriber's instructions and speak to your prescriber or pharmacist before adding any supplement.