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
Free tracker included with every download this week
Which Supplements Are Safe To Take With Mounjaro?
Taking supplements alongside Mounjaro (tirzepatide) is a common question for people starting this prescription weight management injection. The good news is that most standard supplements are safe to take — but some require careful timing or medical advice. Since Mounjaro slows how quickly food leaves your stomach, certain supplements may be absorbed differently. Always discuss any supplements with your prescriber before starting Mounjaro, as individual circumstances vary. Our GLP-1 weight loss calculator can help you understand what to expect from treatment, but your prescriber has the full picture of your personal health.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 And Safety Considerations
Vitamin and mineral supplements are generally safe with Mounjaro, including B vitamins, vitamin D, magnesium, and zinc. However, timing matters — take these at least 2 hours apart from Mounjaro injections if possible. Iron supplements require extra caution, as Mounjaro may affect absorption; discuss with your GP before starting iron supplements. Calcium and antacids can interfere with absorption of some medications — separate them from other tablets by at least 2 hours. Omega-3 supplements (fish oil) are safe and may support cardiovascular health, which is beneficial when losing weight. Avoid high-dose supplements without medical advice — more is not always better. If you're taking tirzepatide, mention every supplement, vitamin, and herbal product to your prescriber, as some may interact with other medications you're taking alongside Mounjaro.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Supplements To Be Cautious About
Herbal supplements need careful consideration — products like St. John's Wort can interfere with medications, and some herbal weight loss supplements may contain undisclosed ingredients. Protein powders are fine to use with Mounjaro, but remember that Mounjaro already reduces appetite significantly, so you may not need as much as before. Some people find protein helps maintain muscle during weight loss — use our progress tracker to monitor changes. Fibre supplements (psyllium husk) may help with constipation, which is a common Mounjaro side effect, but introduce them gradually to avoid bloating. Probiotics are generally safe and may help with digestive side effects. Always check labels — some supplements contain ingredients that slow digestion further, which is unhelpful alongside Mounjaro. Never take weight loss supplements (especially those containing ephedrine or caffeine in high doses) without explicit approval from your prescriber.
- 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 multivitamins while on Mounjaro?
Yes, standard multivitamins are generally safe with Mounjaro. However, space them 2 hours apart from your Mounjaro injection if possible, as the injection affects stomach emptying. If your multivitamin contains iron, discuss timing with your GP. Some nutrients may be absorbed differently due to slower gastric emptying, so your prescriber might recommend checking nutrient levels after a few months.
Should I take supplements for Mounjaro side effects?
Some supplements can help manage side effects. Ginger supplements may support nausea, and fibre supplements can ease constipation — a common side effect. However, introduce any new supplement gradually and inform your prescriber first. Staying hydrated and eating small, frequent meals often helps more than supplements.
Will supplements interfere with how Mounjaro works?
Most standard supplements don't reduce Mounjaro's effectiveness. However, high-dose herbal products or weight loss supplements may interact unpredictably. Since Mounjaro is a prescription-only medication requiring ongoing prescriber monitoring, discuss all supplements at your regular check-ups to ensure nothing compromises your treatment.
Is it safe to take appetite suppressant supplements with Mounjaro?
No — combining appetite suppressant supplements with Mounjaro is not recommended. Mounjaro already suppresses appetite significantly. Adding other appetite suppressants increases the risk of side effects and nutritional deficiency. Your prescriber will advise on appropriate supplement choices for your individual needs.
Can supplements help with nutrient absorption while on Mounjaro?
Yes, in some cases. Mounjaro may reduce absorption of certain nutrients due to slower stomach emptying. If you're concerned about nutrient status, ask your GP about blood tests after 3–6 months of treatment. They may recommend specific supplementation based on your results. Tracking your intake using our progress tracker alongside your GP's guidance ensures you stay on track safely.
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.