What vitamins should I take on Mounjaro?

The core decision: do you need supplements, or just a better plate?

When appetite drops sharply in the first weeks on tirzepatide, many people find they are eating perhaps half what they previously managed. Less food means fewer vitamins arriving naturally. The question is not really "which supplements should I add" but a prior one: is your diet, at its reduced volume, actually covering your bases?

A simple food diary for a week can be revealing. If you are regularly eating less than around 1,200 calories a day, or skipping whole food groups because nothing sounds appealing, micronutrient gaps become likely rather than theoretical. That is the point at which a supplement makes practical sense, not as a substitute for eating well but as a safety net while your appetite recalibrates. For a closer look at which specific supplements are most discussed in this context, the vitamins to take on Mounjaro page goes through each one in detail.

The tirzepatide overview on this site covers how the medicine works and what to expect across the dose-titration period, which is also the period when appetite suppression tends to be strongest and dietary intake most disrupted.

The nutrients most likely to fall short on a reduced-calorie diet

Vitamin D is the UK's most commonly deficient nutrient even without appetite suppression. The NHS recommends all adults consider a daily 10 micrograms supplement, particularly from October through March, and on Mounjaro, when oily fish, eggs, and fortified foods may be eaten less often, the case is stronger. You will find this NHS guidance on diet and healthy weight a useful reference alongside your treatment.

Vitamin B12 matters because it is found almost exclusively in animal products. People who reduce red meat, fish, or dairy while on treatment (whether by choice or because their appetite simply does not draw them there) can see B12 levels drift over several months. B12 deficiency develops slowly and the early symptoms (fatigue, mild tingling) can be mistaken for ordinary tiredness on a lower calorie intake.

Iron and folate follow a similar logic. Folate is plentiful in leafy greens, but those are not always the foods that remain appealing at a reduced appetite. Iron is particularly relevant for women with heavy periods, who may already be borderline. If you are considering changes to your current supplement routine, the page covering what vitamins you need on Mounjaro addresses this in more depth.

Protein is not a vitamin, but it deserves mention here. Preserving lean muscle while losing weight requires adequate protein at each meal, and on a smaller appetite that becomes harder. Prioritising protein-rich foods at every sitting is a consistent piece of clinical advice on GLP-1 medicines.

Timing, absorption, and the gastric-emptying factor

Tirzepatide slows the rate at which food leaves the stomach. That is central to how it reduces appetite, but it also has a practical implication for supplements taken orally: some nutrients and medications may be absorbed more slowly, or at a slightly different rate, than they would be without the medicine. This is not usually a clinical problem for standard vitamins, but it is why prescribers often suggest spacing fat-soluble vitamins (A, D, E, K) across a meal rather than on an empty stomach, and why iron is typically taken separately from calcium-containing supplements anyway.

A practical tip that patients find useful: keep your supplements next to something you reliably reach for every morning. Some people use the fridge door, where the Mounjaro pen already lives, as a prompt to take their vitamin D alongside it before breakfast. Simple, and it removes the "did I take it?" doubt from your day.

For supplements that should be avoided or treated with caution alongside tirzepatide, the page on vitamins that should not be taken with Mounjaro is worth reading before you add anything new to your routine.

What your prescriber should know

Before starting any supplement, tell the prescriber who manages your Mounjaro treatment what you already take. This includes vitamins that feel routine, high-dose vitamin A, for instance, carries teratogenicity risks relevant to women of childbearing age; and high-dose calcium supplements can interfere with iron absorption. More detail on reproductive health considerations is covered in the Mounjaro and birth defects page.

Baseline bloodwork before starting treatment, or shortly after, can catch deficiencies early and give you a number to track. If your GP practice is one of those now participating in the expanded tirzepatide prescribing programme, they may already include some of these checks. Private patients can request a basic micronutrient screen privately or through their GP.

Private treatment costs, including what is included in a consultation, are set out on the Mounjaro cost page, relevant if you are weighing up where to manage your treatment and what ongoing support looks like. A prescriber at a well-run service will ask about your diet and supplements at each clinical review, not just at the start. That is the kind of review our prescribers carry out before every repeat. Our clinical team is GPhC-registered and reviews every consultation personally.