Vitamins and Supplements on Mounjaro: What to Take and Avoid

What vitamins should I take on Mounjaro?

On Mounjaro (tirzepatide), take 10 micrograms of vitamin D a day, October to March, like every UK adult; add B12, iron or calcium when a test shows a gap.^{1, 5}

In short

• Take vitamin D, 10 micrograms a day, from October to March; add B12, iron or calcium when a blood test shows a gap.^{2, 5}
• Avoid St John's wort, herbs sold for blood sugar, caffeine fat burners, vitamin A over 1.5 mg and iron without a blood test.^{6, 13, 15, 19}
• For hair loss, a common side effect, secure protein, iron, zinc and the B vitamins; no vitamin has been tested for it on tirzepatide.^{1, 14}

Evidence at a glance

• Nutrient status on GLP-1 medicines: one 2026 review, 6 studies, 480,825 adults, mainly observational; vitamin D deficiency in 7.5% at six months and 13.6% at twelve; ferritin 26% to 30% lower than in a comparison group.²
• Body composition: in the 160-person substudy of the main tirzepatide trial (six of its eight authors were manufacturer employees), about a quarter of the weight lost was lean tissue, as with placebo.³
• Common side effects on the NHS list include feeling tired and hair loss, alongside the gut effects.¹

Sources checked on 2 November 2026. Checked by the Wellgard Scientific Editorial Team, 1 November 2026.

This page is the hub of the Mounjaro guides. Living well on Mounjaro is the nutrition chapter, and what supplements to take on a GLP-1 medicine is the medicine-neutral version.

Does Mounjaro cause vitamin deficiency?

Not directly, on the evidence so far. The product information says tirzepatide delays stomach emptying and may change how quickly oral medicines are absorbed. No study has measured vitamin or mineral absorption, and the NHS lists no deficiency among its side effects.^{1, 18} What the medicine clearly does is cut appetite, so meals shrink and over months a smaller plate becomes a narrower one.¹ In the 2026 review, vitamin D intake averaged about 20% of the recommended amount and more than 60% of users were below their calcium and iron requirements. Ferritin ran 26% to 30% lower than in people on a different class of diabetes medicine, and B12 deficits grew with time on treatment.² The studies were mainly observational, so they cannot prove the medicine caused the gaps; eating much less, of fewer foods, is the obvious route.²

Do I need to take vitamins on Mounjaro?

Vitamin D in autumn and winter, yes, because that advice is for every adult in the UK.⁵ Beyond that, a supplement earns its place when the food that carried a nutrient has gone. That means eating far less than you used to or skipping meals, having dropped a whole food group, being vegan or vegetarian, taking metformin, being older (B12 is harder to absorb with age), or having had bariatric surgery.^{10, 17} Symptoms overlap with the medicine's own tiredness, so a blood test is the only way to know. A full blood count, ferritin, B12, folate, vitamin D and thyroid function are the ones GPs use, and why am I so tired on Mounjaro walks through the medicine-or-under-eating check.

Which supplements are worth taking on Mounjaro?

Can you take vitamin D with Mounjaro?

Yes. The NHS advice to every adult applies: consider 10 micrograms (400 IU) a day from October to early March, all year if you are rarely outdoors, cover your skin or have dark skin. Take no more than 100 micrograms (4,000 IU) a day.⁵ No interaction with tirzepatide is listed.¹ Vitamin D contributes to the maintenance of normal bones, the maintenance of normal muscle function and the normal function of the immune system.¹⁶ The vitamin D guide sets out D2, D3 and the plant sources with the trials behind each.

Does Mounjaro cause B12 deficiency?

Not in any study so far: no trial has measured B12 absorption on tirzepatide, and the medicine known to lower B12 is metformin.^{10, 18} In the Diabetes Prevention Program follow-up, 2,155 adults randomised to metformin or placebo, low or borderline B12 was found in 19.1% of the metformin group at five years against 9.5% on placebo.¹⁰ B12 comes from meat, fish, eggs, dairy and fortified foods, so months of eating far less of them is the other route. Adults need about 1.5 micrograms a day.^{2, 17} Vitamin B12 contributes to normal red blood cell formation, normal functioning of the nervous system and the reduction of tiredness and fatigue.¹⁶ Tiredness, pins and needles or a sore tongue are among the NHS symptoms, and a B12 level is the test that settles it; signs of B12 deficiency lists the rest.⁹

Mounjaro and iron deficiency

Iron is the one nutrient to test before you supplement. The NHS amounts are 14.8 mg a day for women aged 19 to 49 and 8.7 mg for men and for women over 50. More than 20 mg a day commonly causes constipation, nausea, vomiting and stomach pain.⁶ Iron contributes to normal formation of red blood cells and haemoglobin and to the reduction of tiredness and fatigue.¹⁶ Tiredness, breathlessness, palpitations and paler skin are the NHS symptoms of iron deficiency anaemia; a GP confirms it with a full blood count and ferritin.⁷ Iron supplement side effects covers the rest.

Can you take magnesium with Mounjaro?

Yes. No interaction between magnesium and tirzepatide is documented and no trial has tested the pair; the NHS asks only that a doctor or pharmacist knows what you take.¹ Adults need 300 mg a day (men) or 270 mg (women), from nuts, seeds, wholegrains and leafy greens. More than 400 mg a day from supplements can cause diarrhoea.¹¹ Magnesium contributes to normal muscle function, normal functioning of the nervous system, normal psychological function and the reduction of tiredness and fatigue.¹⁶

Calcium and zinc

Calcium: adults need 700 mg a day, most of it from dairy or fortified plant milk, and the 2026 review recorded more than 60% of users below that.^{2, 12} Calcium is needed for the maintenance of normal bones;¹⁶ do you need a calcium supplement works through the decision. Zinc: 9.5 mg (men) or 7 mg (women) a day, from meat, shellfish, pulses and seeds;¹¹ zinc contributes to the normal function of the immune system and to the maintenance of normal skin.¹⁶

How much protein do you need on Mounjaro?

Keep protein up as food volume falls: the UK reference intake is 0.75 g per kilogram a day, set for people who are not losing weight.²⁰ About a quarter of the weight lost on tirzepatide was lean tissue in the substudy above, and a pooled analysis of 22 trials in 2,258 adults found the same share across GLP-1 medicines.^{3, 4} How much protein you need on Mounjaro gives the per-kilogram targets for weight loss, and does Mounjaro cause muscle loss the trial detail.

Do you need a fibre supplement on Mounjaro?

Adults are advised 30 g of fibre a day and most eat about 20 g; a fibre supplement is reasonable when constipation is a side effect and food cannot get you there.²¹ Constipation is on the NHS list of common tirzepatide side effects, and a smaller plate drops the vegetables, wholegrains and pulses first.¹ How much fibre you need on Mounjaro sets the pace for raising it without bloating.

Do you need electrolytes on Mounjaro?

Only when vomiting or diarrhoea are part of the picture; on an ordinary day food and water cover sodium and potassium.¹ Adults need 3,500 mg of potassium a day, and older people should not take potassium supplements unless a doctor advises it.¹¹ Do you need electrolytes on Mounjaro has the figures for sick days, and for sodium if you watch your blood pressure.

Which vitamins help with hair loss on Mounjaro?

Hair loss is on the NHS list of common tirzepatide side effects, does Mounjaro cause hair loss has the timeline, and the nutrients to secure are protein, iron, zinc and the B vitamins.^{1, 14} The usual mechanism is telogen effluvium, a diffuse shedding set off by a physiological shock such as sudden weight loss, which usually remits.¹⁴ Biotin contributes to the maintenance of normal hair, and zinc contributes to the maintenance of normal hair.¹⁶ Does zinc help with hair loss has the zinc trials, and should you take collagen on Mounjaro where collagen fits.

What vitamins should you NOT take with Mounjaro?

Nothing is off limits because of Mounjaro (tirzepatide) itself: its UK product information names no vitamin, mineral or supplement it must not be taken with, and the NHS asks only that you tell your doctor or pharmacist about any medicines, herbal remedies, vitamins or supplements you take.^{1, 18} The cautions are about amounts and timing: iron without a blood test, vitamin A above 1.5 mg a day and high-dose biotin before a blood test; iron and calcium at different meals; the fat-soluble vitamins A, D, E and K with a meal that contains some fat; and a fibre supplement such as psyllium kept apart from other tablets.^{6, 13, 23} The rest are about what a product carries and what else you take: sugar, alcohol and sugar alcohols in gummies, tonics and syrups (the NHS says it is best to avoid alcohol on tirzepatide); herbs sold for blood sugar, a prescriber conversation if you also take a sulphonylurea or insulin, the one combination the product information flags for low blood sugar; St John's wort, which the NHS says can cause serious problems with anticoagulants and the contraceptive pill; and caffeine products, since coffee is on the NHS list of heartburn triggers.^{1, 15, 18, 19, 22} What vitamins should you not take with Mounjaro is the full answer, item by item, with the product information's own words and the NHS amounts.

Lion's mane and ashwagandha have no study with tirzepatide; lion's mane side effects and what you can take with ashwagandha carry the detail. Stay within the NHS supplement figures across every product you take.¹¹

Do you need a multivitamin on Mounjaro?

A multivitamin covers several nutrients at around the reference intake each. No trial has given one to people on tirzepatide and measured an outcome, so the case rests on the 2026 review's intake findings above.² Read the vitamin A, iron and biotin lines above, and take it with a small snack. "Best multivitamin for women on Mounjaro" has no trial answer; how to choose a multivitamin for women explains what a women's formula should contain at each age. There is no tirzepatide gummy: tirzepatide is a prescription injection, and anything sold as a gummy under the medicine's name is a different product; do GLP-1 supplements work covers what those contain.¹

Every guide in this series

This page is the hub. Nutrition: living well on Mounjaro, what to eat, the 7-day meal plan, what to avoid, alcohol and foods that raise your own GLP-1. Side effects: tiredness, hair loss, Mounjaro face, constipation and diarrhoea, sulphur burps, heartburn and how long side effects last. Women: side effects in women, the pill, HRT and menopause and pregnancy. Also: how Mounjaro works and what happens when you stop.

What we don't know

• No randomised trial has given a vitamin or mineral to people taking tirzepatide and measured deficiency, symptoms or weight.²
• Whether the delayed stomach emptying changes how much of a vitamin or mineral is absorbed, not only when; the product information covers oral medicines, not nutrients.¹⁸
• Whether protein, a multivitamin or both reduce the hair shedding or the lean-tissue share.^{3, 14}

Frequently asked questions

Can you take magnesium glycinate or citrate on tirzepatide?

Yes, either. No interaction with tirzepatide is documented and no trial has tested the pair; the NHS asks only that a doctor or pharmacist knows what you take.¹ Glycinate (bisglycinate) and citrate both deliver magnesium. Compare the label's elemental figure against the 400 mg a day the NHS says is unlikely to cause harm; more than that can cause diarrhoea.¹¹ What is magnesium glycinate and what is magnesium citrate cover each form; neither is ranked above the other.

What vitamins are recommended for GLP-1 users?

The same short list, whichever GLP-1 medicine you take: vitamin D from October to March as for every UK adult, then B12, iron, calcium or a multivitamin when a blood test or a narrowed diet shows the need, with protein and fibre kept up as meals shrink.^{2, 5} The evidence is the same 2026 review of 480,825 adults on GLP-1 medicines, mainly observational; what supplements to take on a GLP-1 medicine is the medicine-neutral guide.²

Can tirzepatide cause anaemia?

Anaemia is not among the side effects the NHS lists for tirzepatide; feeling tired is.¹ Eating much less meat, fish, eggs, dairy and fortified cereal for months can lower iron, B12 and folate. The 2026 review did record lower ferritin and rising B12 deficits.² Iron contributes to normal formation of red blood cells and haemoglobin and vitamin B12 to normal red blood cell formation; neither is a reason to take iron without a result.¹⁶

Should you take a probiotic on tirzepatide?

No trial has tested live cultures in people taking tirzepatide, so there is no evidence that picks one out, and no live-culture product carries a UK authorised health claim.¹⁶ If you already take a live-culture product and it suits you, nothing about tirzepatide changes that; what are probiotics sets out the trials in which live cultures were tested, and for whom.

Do you need B12 injections on tirzepatide?

Only if a blood test shows a deficiency with a cause that tablets cannot fix, and a GP decides. No study has measured B12 absorption on tirzepatide; the risk is months of eating far less animal food.¹⁸ The NHS treats B12 deficiency anaemia with hydroxocobalamin injections when the cause is not dietary, "every 2 to 3 months for the rest of your life" in pernicious anaemia, and with daily tablets, or an injection twice a year, when diet is the cause.⁸ None of the studies cited here gave B12 injections to people with normal levels and measured energy or weight. A test shows whether yours is a B12 question.⁸

Sources

1. NHS. Tirzepatide. Reviewed 15 May 2026. nhs.uk.
2. Urbina J, et al. Micronutrient and nutritional deficiencies associated with GLP-1 receptor agonist therapy: a narrative review. Clinical Obesity, 2026. Narrative review, 6 studies, 480,825 adults, mainly observational; no funding or conflicts listed on PubMed. PubMed 41549912.
3. 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. Scan substudy of a randomised trial, 160 adults, 72 weeks; manufacturer-funded. PubMed 39996356.
4. Karakasis P, et al. Effect of GLP-1 receptor agonists and co-agonists on body composition: systematic review and network meta-analysis. Metabolism, 2025. Pooled analysis, 22 randomised trials, 2,258 adults; authors declare industry fees. PubMed 39719170.
5. NHS. Vitamin D. Reviewed 3 August 2020. nhs.uk.
6. NHS. Vitamins and minerals: iron. Reviewed 3 August 2020. nhs.uk.
7. NHS. Iron deficiency anaemia. Reviewed 26 January 2024. nhs.uk.
8. NHS. Vitamin B12 or folate deficiency anaemia: treatment. Reviewed 20 February 2023 (review overdue). nhs.uk.
9. NHS. Vitamin B12 or folate deficiency anaemia: symptoms. Reviewed 20 February 2023 (review overdue). nhs.uk.
10. Aroda VR, et al. Long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study. Journal of Clinical Endocrinology and Metabolism, 2016. Follow-up of a randomised trial, 2,155 adults, 5 and 13 years; US government funding. PubMed 26900641.
11. NHS. Vitamins and minerals: others (magnesium, potassium, zinc). Reviewed 3 August 2020. nhs.uk.
12. NHS. Vitamins and minerals: calcium. Reviewed 3 August 2020. nhs.uk.
13. NHS. Vitamins and minerals: vitamin A. Reviewed 3 August 2020. nhs.uk.
14. Chien Yin GO, et al. Telogen effluvium: a review of the science and current obstacles. Journal of Dermatological Science, 2021. Narrative review; no funding or conflicts listed on PubMed. PubMed 33541773.
15. NHS. Herbal medicines and complementary therapies. Reviewed 1 May 2026. nhs.uk.
16. Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register, last updated 19 May 2026. gov.uk.
17. NHS. Vitamins and minerals: B vitamins and folic acid. Reviewed 3 August 2020. nhs.uk.
18. Tirzepatide Summary of Product Characteristics, sections 4.4 (hypoglycaemia with a sulphonylurea or insulin) and 4.5 (interactions), electronic medicines compendium, date of revision of the text 29 August 2026. medicines.org.uk.
19. NHS. Depression in adults: treatment (St John's wort). Reviewed 5 July 2023 (review overdue). nhs.uk.
20. Public Health England. Government dietary recommendations: energy and nutrients for males and females aged 1 to 18 years and 19+ years, 2016 (protein 0.75 g per kilogram a day). assets.publishing.service.gov.uk.
21. NHS. How to get more fibre into your diet. Reviewed 2 March 2026. nhs.uk.
22. NHS. Heartburn and acid reflux. Reviewed 20 November 2023. nhs.uk.
23. MHRA. Safety Roundup, May 2025: biotin interference on thyroid function laboratory tests. Issued 29 May 2025. gov.uk.

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General information, not personal medical advice. Mounjaro is a prescription medicine: follow your prescriber's instructions, and speak to your GP or pharmacist before starting a supplement if you take other medicines or have a health condition.