What vitamins do you need to take on Mounjaro?

Does Mounjaro itself deplete vitamins?

Tirzepatide does not directly strip the body of vitamins. The mechanism is appetite suppression and slower gastric emptying, not malabsorption. That distinction matters, because it means supplementation is not automatically necessary in the way it is after bariatric surgery, for example. The NHS tirzepatide medicines page does not list a required supplement regimen, and the prescribing information does not mandate one either.

What the medicine does do is meaningfully reduce how much most people want to eat. If a person moves from 2,000 calories a day to 1,200 on tirzepatide, they are also eating roughly 40% fewer micronutrients unless they are very careful about food quality. That is the real risk, and it is dietary rather than pharmacological. The practical upshot: the better your food choices on treatment, the lower your supplementation burden. Prioritising nutrient-dense meals (vegetables, lean protein, wholegrains, dairy or alternatives) goes a long way.

Still, some people's intake drops far enough to create gaps. Others were already low in certain nutrients before starting. A baseline blood test before or shortly after starting treatment is a sensible step, and it gives your prescriber something concrete to act on rather than speculate about.

Which specific nutrients are worth watching on tirzepatide?

Vitamin D tops the list for most people in the UK regardless of whether they are on tirzepatide. The NHS recommends that everyone in the UK consider a daily 10 microgram supplement during autumn and winter, and people with darker skin tones or limited sun exposure may need it year-round. On a reduced-calorie diet, hitting even the modest dietary contribution from oily fish, eggs and fortified foods becomes harder. This one is practical and inexpensive to address.

Vitamin B12 is worth monitoring if red meat, fish, eggs and dairy are becoming harder to eat in meaningful quantities. B12 is absorbed in the small intestine and is not stored indefinitely; low levels develop slowly, but the consequences (fatigue, neurological symptoms) are real. People who were already vegetarian or vegan before starting treatment should discuss B12 proactively.

Iron, particularly for women of reproductive age, deserves attention if appetite suppression is reducing red meat or fortified-cereal intake. Fatigue on Mounjaro can have several causes; low iron is one of them and is simple to screen for. Calcium and magnesium round out the list for people whose dairy or nut intake has fallen substantially. Our practical guide to vitamins to take on Mounjaro sets out the reasoning behind each nutrient in more detail.

Protein is not a vitamin, but it belongs in this conversation. During weight loss, preserving lean muscle mass depends heavily on adequate protein intake, generally at least 1.2–1.6 g per kg of body weight daily, though your prescriber or dietitian will give you a personal target. When appetite falls sharply, protein is often the first macronutrient to suffer. Prioritising protein at each meal, before filling up on carbohydrates or fats, is the most consistent piece of advice given to people on GLP-1 treatment.

Should I just take a multivitamin to cover everything?

A multivitamin is not harmful for most people, and for some it is a reasonable safety net. However, it is not a substitute for understanding your actual nutritional status. Some multivitamins contain iron, which can cause constipation (already a possible side effect of tirzepatide) so reading labels is worthwhile. Others contain amounts of fat-soluble vitamins (A, D, E, K) that can accumulate if taken alongside food sources, so more is not always better.

The more targeted approach is to identify which nutrients you are actually likely to fall short on, based on your diet before and during treatment, then supplement selectively. If you are eating well and your diet includes a reasonable variety of vegetables, protein sources and dairy or alternatives, a targeted vitamin D supplement and perhaps a B-complex may be all that is realistically needed. If your intake has dropped substantially and you are struggling with fatigue or brain fog, a blood panel will give you a clearer picture than a multivitamin label will. You can explore whether taking vitamins with Mounjaro is actually necessary for your situation, it depends on factors specific to you.

One thing many people on tirzepatide tell our clinical team: they wish they had set up good dietary habits in the first few weeks of treatment, before the appetite suppression became marked. That window, while food still feels accessible and manageable, is the best time to build a routine around protein and micronutrient-rich foods that will carry forward through the dose-increase stages. If you want guidance on which vitamins tend to work best when you are on Mounjaro, that page brings together the options most worth considering. Information on Mounjaro and how it works as a treatment covers the dose schedule in more detail.

How should I get personalised advice on vitamins during treatment?

The honest answer is: from your prescriber. This page gives you a framework, but whether you personally need iron, B12 or anything else depends on a blood test and a conversation about your eating pattern. That is not a deflection, it is the difference between guessing and knowing. The NHS England guidance on weight-management injections emphasises wraparound support including dietary advice as part of responsible treatment, and that principle applies whether you are seen privately or on the NHS.

At nume, every treatment cycle includes a clinical review before any repeat is approved. If you are finding that fatigue or other symptoms are affecting your experience on Mounjaro, that is a conversation worth having. You can also browse what vitamins other people on Mounjaro are advised to consider to see which supplements come up most often in clinical contexts, and our dedicated page on vitamins to take while on Mounjaro goes into further practical detail for people at different stages of treatment. For a broader look at what is involved in starting treatment, our weight-loss treatment overview sets out the options and the process clearly. And if you have questions ready and want to speak to a prescriber directly, you can start your free consultation today.