If you are wondering what supplements you should take while on Mounjaro, the short answer is that you may not need many, or any, extra supplements. A good starting point is to get enough protein from food, follow UK guidance on vitamin D, and make sure you are still getting a varied diet while eating less.
Mounjaro does not create a general requirement for vitamins or minerals. However, because it can reduce appetite and food intake, some people may find it harder to get all the nutrients they need from food.
That is why it makes more sense to look at your diet, symptoms and, where appropriate, blood test results before buying a shelf full of supplements.
This guide covers protein, vitamin D, multivitamins, magnesium and iron, as well as some common supplements that may not be worth buying. It also explains when blood tests may be more useful than guessing.
Key takeaways
- Protein from food should be a priority during weight loss, particularly if you are trying to maintain muscle.
- Vitamin D is recommended for many people in the UK during autumn and winter, regardless of whether they take Mounjaro. Some people may need it all year round.
- A multivitamin is not essential for everyone. It may be useful if you are eating less or your diet has become less varied.
- Blood tests can be more useful than guessing, particularly when there is a concern about iron, B12 or vitamin D.
- Be careful about taking several products together. A multivitamin, B complex and separate mineral supplements can contain the same nutrients.
- No supplement has been shown to make Mounjaro work better. Be cautious of products that make claims about improving or enhancing its effects.
Start With Protein, Not Pills
Before reaching for a supplement, look at how much protein you are getting from your normal diet.
Weight loss can involve a reduction in both body fat and lean tissue. In a body composition study of tirzepatide, most of the weight lost was fat mass, while around a quarter was lean mass. This does not mean everyone will have the same result.
Getting enough protein and doing regular resistance exercise can be useful parts of a weight management plan, but neither can guarantee that you will maintain all of your muscle.
The UK reference nutrient intake for protein is 0.75g per kilogram of body weight for adults. This is a general reference amount and is not specifically designed for people who are actively losing weight or doing regular strength training.
Some people may need more protein depending on their age, body size, activity level and health. If you are unsure how much you need, a dietitian or healthcare professional can give you advice based on your circumstances.
Protein powder can be useful if you find it difficult to get enough protein from food, especially when your appetite is low. It is a convenience product rather than a requirement, and there is no need to use it if you are already getting enough protein from your diet.
Collagen should not be treated as a replacement for a complete protein source. It does not provide the same range of essential amino acids as many complete protein sources.
The Priority Order
You do not need to buy all of these supplements. Think of the list as a way to decide what may be worth looking at first.
| Priority | What | Why |
|---|---|---|
| 1 | Protein from food | Supports a balanced diet and helps provide the building blocks needed for muscle |
| 2 | Vitamin D | Recommended for many people in the UK, particularly during autumn and winter |
| 3 | A basic multivitamin | May be useful if you are eating less or your diet has become less varied |
| 4 | Magnesium, if appropriate | May be useful in some situations, but it is not automatically needed because you take Mounjaro |
| 5 | Other supplements | Consider these when there is a specific reason, such as a confirmed deficiency |
Vitamin D
Vitamin D is worth thinking about, but this is not because Mounjaro causes a vitamin D deficiency.
UK guidance recommends that adults consider taking 10 micrograms (400 IU) of vitamin D each day during autumn and winter. People who are at higher risk of vitamin D deficiency may be advised to take it throughout the year.
Vitamin D is important for healthy bones and muscles. It can be difficult to get enough from food alone, particularly during the months when sunlight is weaker in the UK.
The usual daily amount is 10 micrograms (400 IU). Do not assume that a higher dose is better. The NHS advises adults not to take more than 100 micrograms (4,000 IU) of vitamin D a day unless a healthcare professional has advised a different dose.
If you have been diagnosed with vitamin D deficiency, your clinician may recommend a different dose for a period of time. Follow their advice rather than trying to treat a deficiency yourself.
Is a Multivitamin Worth It?
Not necessarily. A multivitamin is not a requirement when taking Mounjaro.
However, it may be something to discuss with a pharmacist or healthcare professional if you are eating much less than usual or your diet has become less varied. It can be a simpler option than taking several separate supplements.
If you are choosing one, check the label rather than automatically choosing the highest strength product.
| Check | What to look for |
|---|---|
| Vitamin D | Around 10 micrograms unless a healthcare professional has advised a different amount |
| Vitamin B6 | Avoid unnecessarily high doses, particularly if you are already taking other products containing B6 |
| Zinc | Check the total amount if you are taking more than one supplement |
| Magnesium | Check the amount from supplements and avoid adding products together without checking the total |
| "High strength" labelling | A higher dose is not automatically more useful |
| Amounts for each nutrient | Avoid products that do not clearly state how much of each nutrient they contain |
A basic multivitamin usually contains a mixture of vitamins and minerals. The main thing to watch is duplication.
For example, you could take a multivitamin that already contains B6 and then add a B complex and another B6 supplement without realising how much you are taking altogether.
B Vitamins and the Metformin Point
Vitamin B12 is worth paying attention to in some people, particularly if you take metformin.
Metformin can reduce vitamin B12 levels, and the MHRA states that vitamin B12 deficiency is a common side effect. It may affect up to 1 in 10 people taking metformin, with the risk increasing with higher doses and longer treatment.
If you take metformin and have symptoms such as unexplained tiredness, a sore or red tongue, or pins and needles, speak to your healthcare professional. They may decide that a blood test is appropriate.
Do not assume that these symptoms are caused by Mounjaro or a vitamin deficiency. There can be several possible causes.
You do not usually need a B complex simply because you are taking Mounjaro. B vitamins are important nutrients, but taking more does not automatically give you more energy.
B6 also deserves some attention because it can be present in several different supplements. Check the amount in your multivitamin, B complex and any other products you take so that you are not unknowingly taking a high total amount.
Magnesium and Iron
Magnesium
Magnesium is not something everyone needs to supplement while taking Mounjaro.
Some people take magnesium because they have constipation or want to support normal muscle function. However, the type and amount matter.
Some forms, including magnesium citrate, can have a laxative effect. This may be useful for some people with constipation but may make diarrhoea worse in others.
Mounjaro can cause gastrointestinal side effects such as nausea, vomiting and diarrhoea. These can also lead to dehydration and electrolyte disturbances. If you have ongoing vomiting or diarrhoea, it is more important to deal with the cause and maintain adequate fluid intake than to simply add a magnesium supplement.
If you are considering magnesium because of ongoing constipation, diarrhoea or another symptom, speak to a pharmacist or healthcare professional about the most suitable option.
Iron
Iron is best taken when there is a clear reason for it, such as confirmed iron deficiency or advice from a healthcare professional.
Taking iron when you do not need it can cause side effects such as nausea, constipation and stomach discomfort.
If blood tests show that you have iron deficiency, your healthcare professional can advise you on the appropriate treatment and dose. Do not change the dose or schedule yourself just because you have read that alternate day dosing may be better tolerated.
If iron deficiency is found, the reason for the deficiency may also need to be investigated. This is particularly important in men and women who have gone through menopause.
What's Not Worth Buying
- Digestive enzymes. Mounjaro delays gastric emptying, which can contribute to feelings of fullness. That does not mean you have an enzyme deficiency, and there is no good reason to routinely take digestive enzymes because you use Mounjaro.
- Probiotics for nutrient absorption. Probiotics may have a role in some digestive problems, but they should not be used as a general replacement for treating a confirmed nutrient deficiency.
- Fat burners and thermogenic supplements. These products are often marketed for weight loss, but that does not mean they are suitable or effective for someone taking Mounjaro. Some concentrated herbal ingredients can also have safety concerns.
- Chromium, cinnamon extract, bitter melon and similar products. These are often marketed for blood sugar or weight management, but evidence for meaningful weight loss benefits is limited.
- Products claiming to boost Mounjaro. There is no supplement that you need to add to make tirzepatide work. Be cautious of products making strong claims about increasing its effects.
Herbal supplements also deserve some caution. St John's wort can interact with several medicines and can reduce the effectiveness of some hormonal contraceptives. Berberine can also affect blood sugar and may interact with medicines.
If you take prescription medicines, check with a pharmacist before adding herbal supplements.
Ask for a Blood Test
You do not need a blood test for every supplement you might consider. However, testing can be useful when there is a genuine reason to suspect a deficiency.
For example, your healthcare professional may consider tests such as vitamin B12, ferritin, full blood count, folate or vitamin D depending on your symptoms, diet and medical history.
This is usually more useful than buying several supplements and hoping one of them solves the problem.
If you are eating very little, losing weight quickly, or having ongoing nausea or vomiting, speak to your healthcare professional. Persistent vomiting can lead to dehydration and other nutritional problems and may need medical assessment. Mounjaro is known to cause gastrointestinal side effects, including nausea, vomiting and diarrhoea.
Medical Disclaimer
This article is for general information only and does not replace individual medical advice.
You do not automatically need supplements because you take Mounjaro. Your needs can depend on your diet, health, medicines, symptoms and, where appropriate, blood test results.
Speak to a GPhC registered pharmacist, prescriber or another healthcare professional before starting a supplement, particularly if you take other medicines or have an existing health condition.
Do not start, stop or change prescribed medicines based on information in this article.
If you are eating very little or have persistent vomiting or diarrhoea, seek medical advice rather than trying to manage the problem with supplements alone.