The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
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What Supplements Should You Take With Mounjaro?
If you're taking Mounjaro (tirzepatide) for weight management in the UK, you may wonder whether additional supplements are necessary to support your health. Mounjaro works as a GLP-1 and GIP receptor agonist, and some people experience changes in appetite and nutrient absorption that might warrant supplementation. This guide covers evidence-based supplement considerations, what your GP recommends, and how to maintain nutritional balance alongside your Mounjaro KwikPen injections. Always consult your prescriber before starting any new supplements, as some may interact with your medication.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
Key Supplements to Consider When Taking Mounjaro
When taking Mounjaro, certain supplements may help maintain nutritional health, particularly if appetite reduction leads to lower food intake. B vitamins (especially B12) are commonly recommended, as reduced food consumption can sometimes lower intake of this essential nutrient. Iron supplements may be considered, particularly for women, as appetite suppression can reduce dietary iron. Calcium and vitamin D are important for bone health and often underconsumed when calorie intake drops significantly.
- Consider a daily multivitamin formulated for adults to cover micronutrient gaps
- Electrolyte supplementation may be relevant if experiencing diarrhoea or vomiting (common Mounjaro side effects)
- Fibre supplements can help manage constipation, a frequent side effect of tirzepatide
- Discuss any existing supplement routine with your prescriber before continuing
Individual needs vary significantly — your GP or weight management clinic can assess whether you need specific supplements based on your diet, health status, and any deficiencies detected through blood tests.
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
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Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Safety and Interactions — What You Must Know
Not all supplements are safe to take with Mounjaro. Oral contraceptives are less effective when taken with tirzepatide — switching to a barrier method or non-oral contraceptive is recommended. Some supplements may affect medication absorption or efficacy, and herbal products can interact unpredictably with GLP-1 receptor agonists.
- Always inform your prescriber of all supplements, vitamins, and herbal products you take
- Avoid starting supplements without clinical guidance while on Mounjaro dose titration
- Allow at least 4 hours between taking Mounjaro and other oral medications or supplements when possible
- Blood tests may reveal specific nutrient deficiencies — address these with targeted supplementation rather than general multivitamins
Your weight management clinic or GP is the best source for personalised supplement recommendations based on your individual health needs and Mounjaro tolerance.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Can I take a multivitamin with Mounjaro?
Yes, a standard daily multivitamin is generally safe to take with Mounjaro, but timing matters — separate it from your weekly injection by several hours if possible. Discuss your specific multivitamin formula with your GP or prescriber to ensure it won't interact with tirzepatide. Some people find a multivitamin helpful if Mounjaro reduces their appetite significantly.
Is B12 supplementation necessary on Mounjaro?
Not necessarily for everyone, but it's worth discussing with your prescriber. If you're eating significantly less due to appetite suppression, or if blood tests show low B12, supplementation may be beneficial. B12 injections or sublingual supplements are options your GP can prescribe if needed.
What about fibre supplements for Mounjaro constipation?
Fibre supplements like psyllium husk can help manage constipation, a common Mounjaro side effect. Start gradually with any new fibre supplement and ensure you're drinking enough water — too much fibre without sufficient hydration can worsen constipation. Your GP can recommend suitable products.
Can supplements affect how well Mounjaro works?
Potentially. Some supplements may affect medication absorption or interact with tirzepatide. This is why it's essential to tell your prescriber about everything you take — from vitamin D to herbal remedies. They can assess whether any adjustments are needed to your supplement routine.
Should I take supplements if I'm not deficient?
Only with clinical guidance. Taking unnecessary supplements wastes money and carries a small risk of interactions. A blood test through your GP can identify actual deficiencies. Focus on targeted supplementation for confirmed gaps rather than taking everything "just in case."
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.