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, 2} The real cautions are about amounts, about timing around a stomach that empties more slowly, about side effects that stack with the medicine's own, and about what a product's label says it contains.

In short

• The product information covers oral medicines, not nutrients: tirzepatide delays stomach emptying, so a tablet may be absorbed later, with the effect strongest when you start.²
• Space iron from calcium and from fibre supplements, keep zinc off an empty stomach, and hold magnesium to 400 mg a day while the gut is unsettled.^{4, 6, 15}
• Berberine, cinnamon and chromium: the product information flags low blood sugar only with a sulphonylurea or insulin, and the NHS asks anyone on a diabetes medicine to check herbal products with a pharmacist first.^{2, 19}

Sources checked on 1 November 2026.

This page is one spoke of the hub which vitamins to take on Mounjaro, which covers what is worth taking; what supplements to take on a GLP-1 medicine is the medicine-neutral version.

What does the Mounjaro product information say about interactions?

The UK product information lists no vitamin, mineral or food supplement as an interaction; its general statement is that tirzepatide delays gastric emptying and so has the potential to affect the rate of absorption of oral medicines taken at the same time.² It adds that the effect, a lower peak and a later peak, is most pronounced when treatment starts, that no dose adjustments are expected for most oral medicines, and that people on medicines with a narrow therapeutic index, warfarin and digoxin are its examples, should be monitored at the start and after each dose increase.² The one oral product it singles out is the combined contraceptive pill: a single dose lowered the pill's hormone levels, a change the product information calls not clinically relevant in women of normal BMI, but because reduced efficacy cannot be excluded in women who are overweight or obese it advises a non-oral method or an added barrier method for four weeks after starting and after each dose increase; the NHS gives that four-week barrier advice to everyone on the medicine.^{1, 2} Does Mounjaro affect the pill, HRT and menopause has that study and what it means for oral HRT.

The NHS list of medicines that may not mix well is short: other diabetes medicines such as gliclazide, glimepiride, metformin and tolbutamide, insulin (the dose may need adjusting), warfarin and other anti-clotting medicines, and a general anaesthetic or sedative for an operation.¹ Nothing on either list is a vitamin. What follows is the case for care with each supplement people ask about, and where the case is thin.

Which vitamins and minerals need spacing or timing on Mounjaro?

Iron and calcium, which block each other in the gut; zinc, which makes people feel sick on an empty stomach; and magnesium, whose loose-stool threshold matters more on a medicine that already causes diarrhoea.^{2, 4, 6, 7} None of these is a tirzepatide interaction; they are the ordinary rules of the minerals, which matter more when meals are small and few.

Iron and calcium apart. The licensed product information for a standard iron tablet says absorption of oral iron is reduced by calcium salts and magnesium salts, that tea, eggs and milk can inhibit it, and that iron in turn reduces the absorption of zinc.⁴ So a calcium tablet, a magnesium tablet and an iron tablet go at different meals, and iron does not go down with the milky coffee. The NHS amounts are 14.8 mg of iron a day for women aged 19 to 49 and 8.7 mg for men and for women aged 50 and over; more than 20 mg a day commonly causes constipation, nausea, vomiting and stomach pain, which are the medicine's side effects too, and 17 mg or less is unlikely to cause harm.³ Iron contributes to normal formation of red blood cells and haemoglobin, and calcium is needed for the maintenance of normal bones;²⁷ the NHS calcium figures are 700 mg a day, with more than 1,500 mg linked to stomach pain and diarrhoea.⁵ Iron is the one nutrient to test before you take it; how to choose an iron supplement reads the elemental figure on a label.

Zinc with food. In a double-blind crossover trial, 47 healthy volunteers took 150 mg of zinc a day or placebo for six weeks; symptoms including nausea, abdominal cramps, loss of appetite and vomiting were reported by 84% of the women and 18% of the men, and five women withdrew for gastric irritation.⁷ That dose is six times the NHS line, which is not to take more than 25 mg of zinc a day from supplements unless a doctor advises it, because high doses also reduce the copper the body can absorb.⁶ Zinc contributes to the normal function of the immune system;²⁷ on a medicine where nausea affected 25 to 29% of people in the weight-management trials against 8.5% on placebo, a zinc tablet goes with a meal, not before one.² What should you not take with zinc has the iron-to-zinc ratio and the antibiotic gaps.

Magnesium at 400 mg or less. The NHS says more than 400 mg of magnesium a day from supplements for a short time can cause diarrhoea and that 400 mg or less is unlikely to cause harm; adults need 300 mg (men) or 270 mg (women) a day, most of it from food.⁶ Diarrhoea affected 19 to 23% of people on tirzepatide in the weight-management trials against 7.8% on placebo, so the elemental magnesium on the label is the number to read, whichever form you choose; the forms differ in how much elemental magnesium a capsule carries, so the elemental figure, not the form name, is the number to compare.² Magnesium contributes to normal electrolyte balance.²⁷ What should you not take with magnesium covers the antibiotics and thyroid medicine it binds.

Do fat-soluble vitamins still absorb when you eat much less fat?

Yes, but less efficiently when a dose goes down without any fat, so vitamins A, D, E and K are best taken with the meal that contains some, and their NHS upper figures are the ones to watch, because the body stores what it does not need.^{8, 9, 10, 11, 12} In a trial of 50 healthy older adults, a single vitamin D3 dose taken with a meal containing 30% of its calories as fat produced a peak blood level 32% higher (95% confidence interval 11% to 52%) than the same dose with a fat-free meal, and the type of fat made no difference.⁹ We found no study measuring vitamin absorption in people on tirzepatide, and the NHS lists no deficiency among its side effects; the point is practical, not a warning.^{1, 2}

• Vitamin D: 10 micrograms a day in autumn and winter for every UK adult, and no more than 100 micrograms (4,000 IU) a day, because too much can cause calcium to build up and weaken bones and damage the kidneys and heart.⁸ Vitamin D contributes to normal absorption and utilisation of calcium and phosphorus.²⁷ What should you not take with vitamin D lists the seven medicine groups the NHS names.
• Vitamin A: some research suggests more than an average of 1.5 mg a day over many years may make bones more likely to fracture, and many multivitamins and fish liver oils carry it, so add the two before taking both.¹⁰
• Vitamin E: what the body does not need immediately is stored, there is not enough evidence on high doses, and 540 mg (800 IU) or less a day is unlikely to cause harm.¹¹
• Vitamin K: about 1 microgram a day for each kilogram of body weight, stored in the liver, with 1 mg or less a day from supplements unlikely to cause harm.¹² Vitamin K contributes to normal blood clotting, which is why the NHS tells people on warfarin not to take vitamin K supplements at all, and the tirzepatide page flags warfarin too.^{1, 13, 27}

Should you avoid fibre supplements on Mounjaro?

No, but a bulk fibre such as psyllium (ispaghula husk) has timing rules of its own: at least half an hour to an hour away from other medicines, always in a full glass of water, and not immediately before bed.¹⁵ The licensed product information for ispaghula husk says the absorption of medicines taken with it, minerals and vitamin B12 among them, may be delayed, which is why the gap exists; it warns that a bulk fibre taken without enough fluid can obstruct the throat or oesophagus; and it says people with diabetes should take it only under medical supervision because their diabetes treatment may need adjusting.¹⁵ Tirzepatide is an injection, so the gap is for the tablets and the minerals you take, not the medicine.²

The reason to keep fibre up is stronger than the reason to be careful. Constipation is on the NHS list of common tirzepatide side effects, the UK target is 30 g of fibre a day and most adults eat about 20 g, and a smaller plate loses the vegetables, pulses and wholegrains first.^{1, 14} A supplement is a top-up when food cannot get you there, taken each time in a full glass of water, because the licensed product information warns that a bulk fibre with too little fluid can obstruct the throat or oesophagus; the NHS constipation advice is to increase fibre gradually and to drink plenty of water and other fluids.^{15, 30} How much fibre do you need on Mounjaro has the food list, and why Mounjaro causes constipation and diarrhoea the kiwi, prune and psyllium trial.

Are electrolyte drinks and salt products a problem on Mounjaro?

Not on a sick day, which is what they are for; the caution is the sodium total on an ordinary day, read against the NHS limit of 6 g of salt, around one level teaspoon.¹⁶ The product information says nausea, vomiting and diarrhoea may lead to dehydration, which could worsen kidney function, and asks patients to take precautions to avoid fluid depletion and electrolyte disturbances, particularly older people.² On a day with vomiting or diarrhoea an electrolyte sachet does that job. On a day without, food and water cover sodium and potassium, and a high-sodium sports sachet taken daily adds salt to a diet the NHS already wants lower, which matters most if you watch your blood pressure.¹⁶ Read the sodium per sachet and the potassium if you take a blood-pressure medicine; the NHS says older people should not take potassium supplements unless a doctor advises it.⁶ Do you need electrolytes on Mounjaro sizes a sachet for a light-eating day against one for heavy sweating.

What about sugar, alcohol and sugar alcohols in gummies, tonics and syrups?

Check three label lines: free sugars against the NHS limit of 30 g a day for adults, alcohol in a tonic or tincture because the NHS says it is best to avoid alcohol on tirzepatide, and polyols such as sorbitol or maltitol, which carry a legal laxative warning above 10% of the product.^{1, 17, 18} Free sugars include any sugar added to a product and the sugars in honey and syrups, so a syrupy tonic or a sugared gummy counts towards the 30 g.¹⁷ The NHS advises avoiding alcohol while using tirzepatide because it can increase feeling or being sick; can you drink alcohol on Mounjaro has the 14-unit line.¹ A product with more than 10% added polyols must state that excessive consumption may produce laxative effects, a sensible thing to know on a medicine on which diarrhoea is already common, although the tolerance trials behind that statement used tens of grams, far more than a gummy serving, as sugar and sweeteners in gummy vitamins sets out.^{2, 18} Gummies themselves are not the problem: do vitamin gummies actually work has the two trials in which a gummy matched or beat a tablet.

Can you take berberine, cinnamon, chromium or bitter melon with Mounjaro?

The product information flags low blood sugar for one combination only, tirzepatide with a sulphonylurea or insulin; if you take either, anything sold for blood sugar is a prescriber conversation first, and even if you take neither, the NHS asks anyone on a diabetes medicine to check a herbal product with a pharmacist before starting it.^{2, 19} Its words are that patients receiving tirzepatide in combination with an insulin secretagogue (for example, a sulphonylurea) or insulin "may have an increased risk of hypoglycaemia", and that the risk "may be lowered by a reduction in the dose of the insulin secretagogue or insulin".² The NHS puts medicines for diabetes among those that do not mix well with herbal medicines, which may cause harmful effects or stop your medicine working, and says to check with a pharmacist first if you already take other medicine.¹⁹ Ispaghula husk's own product information carries the same supervision note for people with diabetes.¹⁵

Chromium has an authorised claim, chromium contributes to the maintenance of normal blood glucose levels, and the NHS says 10 mg or less a day from food and supplements is unlikely to cause harm, far above the 25 micrograms adults need.^{6, 27} Berberine, cinnamon and bitter melon have no UK authorised claim, bitter melon's blood-glucose claim is on the register's non-authorised list, and we found none tested alongside tirzepatide; can you take berberine with or after Mounjaro sets out berberine's own trials, what it adds on the medicine, and the hypo risk that belongs to gliclazide and insulin rather than to berberine. St John's wort is a different case: the NHS says taking it with other medicines such as anticoagulants and the contraceptive pill can cause serious problems, and tells people on warfarin not to take it; the NHS adds that doctors do not recommend it because the amount of active ingredient varies between brands and batches, so it stays off the list.^{13, 20}

Should you avoid caffeine, energy drinks and fat burners on Mounjaro?

No interaction between caffeine and tirzepatide is documented; the case for care is that coffee and cola sit on the NHS lists of things that cause or worsen heartburn and indigestion, both in the medicine's list of adverse reactions, and a concentrated caffeine product delivers more of the same.^{1, 2, 22, 23} The NHS names coffee among the food and drink that cause or worsen heartburn and tells people with indigestion to cut down on tea, coffee, cola or alcohol; gastro-oesophageal reflux disease and dyspepsia are both in the tirzepatide product information's list of adverse reactions.^{2, 22, 23} For nausea the NHS advice is smaller, more frequent meals, regular sips of a cold drink and no hot, fried or greasy food, none of which describes a strong black coffee before breakfast.²⁴

The European Food Safety Authority put single doses of caffeine up to 200 mg, about three milligrams per kilogram of body weight, and daily intakes up to 400 mg as raising no safety concerns for healthy adults other than pregnant women; a drink with more than 150 mg of caffeine per litre must be labelled high caffeine content and not recommended for children or pregnant or breastfeeding women.^{18, 21} Many "fat burner" or "metabolism" capsules carry caffeine: read the caffeine line, add it to your coffee and tea before deciding, take one with food if you take it at all, and know that we found no such product tested with tirzepatide.²¹ Energy drinks, unless labelled sugar-free, combine the caffeine with the free sugars above.^{17, 18}

Is protein powder something to avoid on Mounjaro?

No; protein is the nutrient a small appetite most needs to protect, because protein contributes to the maintenance of muscle mass, and a powder is one way to reach a target that food is failing to meet.²⁷ The UK reference intake is 55.5 g of protein a day for men and 45 g for women aged 19 to 64, set for people who are not losing weight.²⁵ Nothing in the product information bears on protein, and a shake is often the meal a nauseous morning can manage; the one timing point is the ispaghula gap above if your powder also carries bulk fibre.^{2, 15} How much protein do you need on Mounjaro gives the per-kilogram targets for weight loss and the trial behind them, and should you take collagen on Mounjaro covers where collagen fits beside it.

What should you do instead of guessing?

Test rather than guess, tell the pharmacist what you take, and treat a supplement as the answer to a measured gap or a named side effect rather than as insurance.¹ The NHS line for tirzepatide is to tell your doctor or a pharmacist about any other medicines, herbal remedies, vitamins or supplements; a pharmacist with your full list can space the minerals and spot the one combination that matters.¹ Vitamin D in autumn and winter is the standing advice for every UK adult; iron, B12, folate and ferritin are the tests to ask for after months of eating less.^{1, 8} What supplements to take on a GLP-1 medicine works through protein, fibre, electrolytes, magnesium and the tests, and the hub which vitamins to take on Mounjaro has the UK amount and NHS supplement figure for each nutrient in one table.

When should you ask the pharmacist or prescriber first?

Before adding anything if you take warfarin, digoxin, insulin or a sulphonylurea; before an iron or potassium supplement without a blood result; before a high-dose biotin product if a blood test is coming; and on any day you cannot keep fluids down.^{1, 2, 3, 6, 26} The product information names warfarin and digoxin as the narrow-therapeutic-index medicines to monitor when tirzepatide starts or steps up, and the sulphonylurea and insulin combination as the one with a hypoglycaemia risk.² The MHRA says biotin may interfere with thyroid immunoassays, more so at higher doses, and asks clinicians to check biotin intake because it can produce falsely high or low results, so tell whoever takes your blood.²⁶ The NHS says very high doses of iron can be fatal, particularly for children, so the jar stays out of reach.³ And the product information's dehydration warning is the reason a day of vomiting or diarrhoea is a call to the pharmacist or prescriber, not a day to experiment.²

Mounjaro is a medicine, so a suspected side effect of the medicine itself goes to the MHRA Yellow Card scheme, which also takes reports on herbal remedies. A problem with a food supplement is reported to your local authority's food safety team.^{28, 29}

What we don't know

Searched 1 November 2026: PubMed, the NHS tirzepatide page and the product information.

• Whether tirzepatide changes how much of a vitamin or mineral is absorbed, rather than when: the product information documents the effect for oral medicines, and we found no study measuring nutrient absorption on the medicine.²
• Whether the half-hour to one-hour gap in the ispaghula product information is enough when the stomach is also emptying more slowly; we found nothing testing the two together.^{2, 15}
• Whether berberine, cinnamon, chromium or bitter melon alter blood sugar in people taking tirzepatide without insulin or a sulphonylurea; we found no trial that gave any of them to medicine users.²
• Whether caffeine worsens tirzepatide's nausea or reflux beyond what it does in anyone; the NHS lists are general, not medicine-specific.^{22, 23}

Frequently asked questions

What supplements can you not take with Mounjaro?

None is forbidden by the product information. The ones to leave out without a reason are iron without a blood result, vitamin A above 1.5 mg a day in total, more than 25 mg of zinc or 400 mg of magnesium from supplements, high-dose biotin before a blood test, St John's wort if you take warfarin or the pill, and anything sold for blood sugar if you also take a sulphonylurea or insulin.^{2, 3, 6, 10, 13, 26}

Does Mounjaro interact with caffeine?

No interaction is documented in the product information or on the NHS page.^{1, 2} Coffee and cola are on the NHS lists of things that cause or worsen heartburn and indigestion, which are also side effects of the medicine, so caffeine lands harder on an empty, slow stomach; with food, within EFSA's 400 mg a day, it is a comfort question rather than a safety one.^{21, 22, 23}

Can you drink energy drinks on Mounjaro?

Nothing bans them, but they stack the caffeine, the free sugars and sometimes the polyols this page covers, and a drink over 150 mg of caffeine per litre carries a legal high-caffeine warning.^{17, 18} A sugar-free version taken with food and counted into your 400 mg of caffeine for the day is the compromise if you want one.²¹

Which two vitamins or minerals should not be taken together?

Iron and calcium, because calcium salts reduce iron absorption; iron and zinc, because iron reduces zinc absorption; and a bulk fibre with any mineral tablet, because the fibre delays its absorption.^{4, 15} None of these pairs is harmful together; they are simply less well absorbed, so a different meal solves it.

What medication can you not take with Mounjaro?

That is a question for your prescriber or pharmacist with your full list, not for a supplement page. The NHS names other diabetes medicines, insulin (the dose may need adjusting), warfarin and other anti-clotting medicines, and anaesthetics or sedatives for an operation, and the product information asks for monitoring of narrow-therapeutic-index medicines such as warfarin and digoxin when the medicine starts or steps up.^{1, 2}

Sources

1. NHS. Tirzepatide. Page last reviewed 15 May 2026. nhs.uk.
2. Tirzepatide Summary of Product Characteristics, sections 4.2, 4.4, 4.5 and 4.8, electronic medicines compendium, date of revision of the text 29 August 2026. Licensed product information; manufacturer document. medicines.org.uk.
3. NHS. Vitamins and minerals: iron. Page last reviewed 3 August 2020 (review overdue). nhs.uk.
4. Ferrous fumarate 210 mg tablets, Summary of Product Characteristics, section 4.5, electronic medicines compendium, date of revision of the text October 2025. Licensed product information; manufacturer document. medicines.org.uk.
5. NHS. Vitamins and minerals: calcium. Page last reviewed 3 August 2020 (review overdue). nhs.uk.
6. NHS. Vitamins and minerals: others (magnesium, zinc, potassium, chromium). Page last reviewed 3 August 2020 (review overdue). nhs.uk.
7. Samman S, Roberts DC. The effect of zinc supplements on plasma zinc and copper levels and the reported symptoms in healthy volunteers. Medical Journal of Australia, 1987. Double-blind crossover trial, 47 adults, 150 mg of zinc a day for six weeks; non-US government research support recorded on PubMed, funder not named. PubMed 3547053.
8. NHS. Vitamin D. Page last reviewed 3 August 2020 (review overdue). nhs.uk.
9. Dawson-Hughes B, et al. Dietary fat increases vitamin D-3 absorption. Journal of the Academy of Nutrition and Dietetics, 2015. Randomised three-group absorption trial, single 50,000 IU dose, 50 healthy older adults; funding not stated on PubMed. PubMed 25441954.
10. NHS. Vitamins and minerals: vitamin A. Page last reviewed 3 August 2020 (review overdue). nhs.uk.
11. NHS. Vitamins and minerals: vitamin E. Page last reviewed 3 August 2020 (review overdue). nhs.uk.
12. NHS. Vitamins and minerals: vitamin K. Page last reviewed 3 August 2020 (review overdue). nhs.uk.
13. NHS. Warfarin. Page last reviewed 24 February 2026. nhs.uk.
14. NHS. How to get more fibre into your diet. Page last reviewed 2 March 2026. nhs.uk.
15. Ispaghula husk granules, Summary of Product Characteristics, sections 4.2, 4.4 and 4.5, electronic medicines compendium, date of revision of the text 1 December 2020. Licensed product information; manufacturer document. medicines.org.uk.
16. NHS. Salt in your diet. Page last reviewed 17 April 2023 (review overdue). nhs.uk.
17. NHS. How does sugar in our diet affect our health? Page last reviewed 19 May 2023 (review overdue). nhs.uk.
18. Regulation (EU) No 1169/2011 on the provision of food information to consumers, as retained in UK law, Annex III (polyols; high caffeine content). Legislation. legislation.gov.uk.
19. NHS. Herbal medicines and complementary therapies. Page last reviewed 1 May 2026. nhs.uk.
20. NHS. Depression in adults: treatment (St John's wort). Page last reviewed 5 July 2023 (review overdue). nhs.uk.
21. European Food Safety Authority. Caffeine: scientific opinion on the safety of caffeine, published 27 May 2015. Agency opinion. efsa.europa.eu.
22. NHS. Indigestion. Page last reviewed 5 May 2023 (review overdue). nhs.uk.
23. NHS. Heartburn and acid reflux. Page last reviewed 20 November 2023. nhs.uk.
24. NHS. Feeling sick (nausea). Page last reviewed 17 November 2023. nhs.uk.
25. Public Health England. Government dietary recommendations: energy and nutrients for males and females aged 1 to 18 years and 19+ years, 2016, Table 2 (protein 55.5 g and 45 g a day; salt less than 6 g; fibre 30 g). Government reference tables. assets.publishing.service.gov.uk.
26. MHRA. Safety Roundup, May 2025: biotin interference on thyroid function laboratory tests. Regulator safety communication, issued 29 May 2025 (published on gov.uk 13 June 2025). gov.uk.
27. Department of Health and Social Care. Great Britain nutrition and health claims (NHC) register. Register of authorised claims. gov.uk.
28. Food Standards Agency. How to report a food safety or hygiene issue for members of the public. Updated 5 August 2026. gov.uk.
29. MHRA. The Yellow Card scheme: guidance for healthcare professionals, patients and the public (reports accepted for all medicines including herbal medicines and homeopathic remedies). Last updated 24 July 2025. gov.uk.
30. NHS. Constipation. Page last reviewed 26 October 2023. nhs.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.