There is no single branded multivitamin that is officially the "best" for women taking Mounjaro. For many people, a simple multivitamin that provides sensible amounts of essential vitamins and minerals can be a practical option, particularly if eating less has made it harder to get a wide range of nutrients from food.
For women in the UK taking Mounjaro (tirzepatide) for weight management, the main question is not which supplement has the strongest marketing claims. It is whether you are getting enough essential nutrients from your diet and whether a supplement is actually needed.
Mounjaro is a Prescription Only Medicine. Tirzepatide acts on GIP and GLP 1 receptors and can reduce appetite, which may lead to lower food intake. Supplements are regulated as foods rather than medicines in the UK, so a multivitamin is not a treatment for Mounjaro side effects and is not proven to make Mounjaro work better. The useful approach is to understand when a supplement might help, which nutrients are worth checking, and when a blood test or advice from a healthcare professional is more appropriate.
Key things to know
- There is no single "best" branded multivitamin for women taking Mounjaro
- Eating less during treatment can make it harder to get enough of some vitamins and minerals from food
- Vitamin D, iron and calcium are among the nutrients worth paying attention to, particularly if your diet has become more limited
- Protein and overall food quality matter too. A multivitamin cannot replace a balanced diet
- Electrolyte drinks may be useful when you have significant fluid losses from vomiting or diarrhoea, but they are not normally needed as a daily replacement for water
- Contraception and pregnancy planning are important to discuss with your prescriber when taking Mounjaro
Do You Need a Multivitamin on Mounjaro?
Not automatically. Mounjaro can reduce appetite, so you may eat less overall. If your meals become smaller or less varied, your intake of some vitamins and minerals can also fall.
A multivitamin can be useful if your diet is limited, but it is not a requirement for everyone taking Mounjaro. Ideally, it should complement a varied diet rather than replace it.
It is also worth paying attention to protein, fibre and fluids while you are losing weight. If you have vomiting or diarrhoea, replacing lost fluids is more important than simply taking an electrolyte supplement.
What the Evidence Actually Shows
A 2026 review in Clinical Obesity looked at six studies involving more than 480,000 adults taking GLP 1 receptor agonists, including medicines such as tirzepatide. It found that vitamin D deficiency became more common over time, iron stores were lower in GLP 1 users than in one comparison group, and more than 60% of participants had calcium and iron intakes below estimated requirements. Vitamin D intake was also relatively low.
However, this research does not prove that Mounjaro directly causes vitamin or mineral deficiencies. The studies were mainly observational, and people's diets and health conditions can also affect nutrient levels.
The findings do give a useful reason to pay attention to nutrition during treatment, particularly if your appetite is much lower or you are struggling to eat a varied diet. If you have symptoms of a possible deficiency, a blood test may be more useful than simply adding several supplements.
Choosing a Multivitamin: What to Check on the Label
You do not need a multivitamin specifically marketed for people taking weight loss injections. Instead, look at the actual nutrient amounts on the label.
| Look for | Be wary of |
|---|---|
| Clear amounts for each vitamin and mineral | "Proprietary blends" where individual amounts are not clear |
| Sensible amounts of essential vitamins and minerals | Very high doses without a clear reason |
| Vitamin D and other nutrients that may be missing from your diet | Claims that the product makes Mounjaro work better |
| Iron if you need it and have no reason to avoid it | Taking extra iron without knowing whether you need it |
| Folic acid if you could become pregnant | Several products containing the same nutrients |
| Clear instructions and a reputable UK manufacturer | Products making broad medical or weight loss claims |
| A form you can tolerate without worsening nausea | Supplements that make your stomach symptoms noticeably worse |
A standard multivitamin can be a reasonable choice if your diet is limited, but more is not necessarily better. High dose supplements can sometimes cause side effects or lead to excessive intake when several products are taken together.
Nutrients Worth Paying Attention to for Women
The amounts you need depend on your age, diet, health and whether you could become pregnant. The figures below are useful UK reference points rather than instructions to take a particular supplement.
| Nutrient | UK Reference Amount |
|---|---|
| Vitamin D | 10 micrograms (400 IU) a day |
| Iron | 14.8mg a day for women aged 19 to 50 |
| Calcium | 700mg a day for adults |
| Folic acid | 200 micrograms a day for adults; 400 micrograms a day when trying to conceive and during the first 12 weeks of pregnancy |
| Vitamin C | 40mg a day for adults |
| Zinc | 7mg a day for women |
These are reference amounts, not targets that everyone needs to reach through supplements. Your needs can be different if you have a diagnosed deficiency, a restricted diet, heavy periods, a medical condition or another reason for increased nutritional requirements.
Vitamin B12 is another nutrient worth considering, particularly if you eat little or no meat, fish, eggs or dairy. The UK reference nutrient intake for adults is 1.5 micrograms a day.
Protein also matters during weight loss. A multivitamin cannot provide protein or replace foods such as eggs, fish, lean meat, dairy products, beans, lentils and other protein rich foods.
Women Over 40: Bone Health
Calcium and vitamin D are important for maintaining normal bones throughout adulthood. This is not specific to Mounjaro, but it becomes increasingly useful to pay attention to bone health as you get older.
Vitamin D intake is particularly relevant in the UK because sunlight exposure is limited during part of the year. UK guidance recommends that adults consider taking 10 micrograms of vitamin D a day during autumn and winter. Some people may need it throughout the year, depending on their circumstances.
You can also get calcium from foods such as milk, yoghurt, cheese and calcium fortified alternatives. A supplement is not automatically needed if your diet already provides enough.
If you have concerns about bone health, repeated fractures or a known vitamin D or calcium deficiency, speak to your GP or another healthcare professional rather than simply increasing your supplement dose.
Iron: What Women Need to Know
Women who have periods generally need more iron than men because of monthly blood loss. The UK reference nutrient intake for women aged 19 to 50 is 14.8mg a day. After menopause, the reference amount is lower.
Taking extra iron is not automatically a good idea, though. Iron supplements can cause constipation, stomach pain, nausea and other digestive problems, which may be particularly unpleasant if Mounjaro already affects your digestion.
If you have persistent tiredness, weakness, breathlessness, heavy periods or other symptoms that could suggest iron deficiency, a blood test can help establish whether you actually need iron.
If iron deficiency is confirmed, your healthcare professional can recommend an appropriate treatment and dose. New iron deficiency after menopause, or in men, may also need investigation to find the underlying cause rather than simply treating it with a supplement.
Contraception, Pregnancy and Folic Acid
Mounjaro should not be used during pregnancy. If you are planning a pregnancy, current product information advises stopping tirzepatide at least 1 month before the planned pregnancy. The MHRA also advises people using GLP 1 medicines to avoid pregnancy while taking treatment.
Mounjaro can reduce the effectiveness of oral contraception in people who are overweight or obese. If you use the contraceptive pill, current guidance recommends adding a barrier method such as condoms for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. Another option is to discuss a non oral contraceptive method with a healthcare professional.
If you could become pregnant, folic acid is also important. The usual UK recommendation is 400 micrograms a day when trying to conceive and during the first 12 weeks of pregnancy. Speak to your GP, pharmacist or prescriber if you need advice about which pregnancy supplement is suitable for you.
Does This Apply if You Are on Wegovy Instead?
Many of the general nutrition points also apply to people taking Wegovy (semaglutide). Both medicines can reduce appetite, which may mean you eat less and have a smaller overall intake of some nutrients.
However, the evidence discussed above looked at a mixed group of GLP 1 medicines rather than tirzepatide alone. It therefore should not be treated as proof that everyone taking Mounjaro or Wegovy will develop a vitamin or mineral deficiency.
If you take Wegovy, check the advice for your own medicine and speak to your healthcare professional if you have symptoms or concerns about your diet.
What About Vitamin Injections?
Vitamin injections are not a routine requirement simply because you take Mounjaro.
For example, vitamin B12 injections are generally used when there is a confirmed or strongly suspected deficiency or another clinical reason for treatment. They are not a general replacement for a multivitamin and are not needed simply to make Mounjaro treatment more effective.
If you are considering a vitamin injection because you feel tired or unwell, it is better to discuss the symptoms with a healthcare professional. Depending on your symptoms and medical history, they may recommend blood tests before deciding whether treatment is needed.
Symptoms That May Need a Blood Test, Not a Guess
Feeling tired can happen for many reasons, including eating less, poor sleep, stress or weight loss. It can also be linked to conditions such as iron deficiency or vitamin B12 deficiency.
Other symptoms such as hair thinning, mouth ulcers, muscle weakness or pins and needles can also have several possible causes. They should not automatically be blamed on Mounjaro or treated with supplements without checking what is going on.
If symptoms are persistent, getting worse or affecting your daily life, speak to your GP, pharmacist or prescriber. A blood test may be more useful than trying several supplements at the same time.
If you develop severe or persistent stomach pain, particularly pain that spreads to your back, seek urgent medical advice because this can be a symptom of acute pancreatitis, which is an uncommon but serious side effect of tirzepatide.
Medical Disclaimer
This article is for general information only and does not constitute medical advice. Mounjaro (tirzepatide) is a Prescription Only Medicine and should only be used under the supervision of an appropriate healthcare professional.
Supplements are regulated as foods rather than medicines in the UK. They may not be suitable for everyone, and taking several products together can result in excessive intake of some nutrients.
Speak to your GP, pharmacist or prescriber before starting a new supplement if you are pregnant, planning a pregnancy, breastfeeding, taking other medicines, or have a diagnosed medical condition or nutritional deficiency.
