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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Best Supplements While Taking Mounjaro
If you're taking Mounjaro (tirzepatide) for weight management, nutritional support becomes important because the medication can affect how your body absorbs certain nutrients and how much food you consume. This guide covers the supplements that may help support your health whilst on Mounjaro treatment, how Mounjaro and Wegovy differ in their nutritional requirements, and what your prescriber should know about any supplements you're taking. Always discuss any new supplements with your GP or prescriber before starting.
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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.
Nutritional Gaps on Mounjaro and Wegovy
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) can reduce appetite and food intake, which may lead to lower nutrient absorption if meals become too restrictive. Key nutritional considerations include:
- B vitamins: Reduced food intake may lower B12, B6, and folate levels — particularly important if you're eating less animal protein
- Iron: Reduced meat consumption or smaller portions may affect iron intake, especially for women of reproductive age
- Calcium and vitamin D: Essential for bone health, particularly during weight loss when bone density can decrease
- Protein: Maintaining adequate protein intake (1.2–2g per kg body weight) helps preserve muscle mass during weight loss
- Electrolytes: Nausea and diarrhoea — common side effects of both medications — can affect sodium and potassium balance
Neither Mounjaro nor Wegovy directly causes nutrient deficiency, but eating smaller portions increases the importance of nutrient-dense foods and targeted supplementation.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Supplements to Discuss With Your Prescriber
Before taking any supplement on Mounjaro, discuss with your GP or prescriber because some supplements can affect how well your medication works or interact with your treatment. Key supplements to consider discussing include:
- Vitamin B12: Often recommended if you're eating less or following a restrictive diet — available as oral, sublingual, or injection forms
- Multivitamins: A quality multivitamin covering B vitamins, iron, calcium, and vitamin D may help if your diet becomes restricted
- Protein powder: Supports muscle preservation during weight loss — whey, plant-based, or collagen options are all suitable
- Oral contraceptives: If you take the contraceptive pill, note that Mounjaro can reduce its absorption — your prescriber may suggest adding a barrier method for 4 weeks after starting or dose increases
Timing matters too — take oral supplements at least 4 hours apart from your injection day if possible, as GLP-1 medications slow gastric emptying.
- 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 vitamins whilst on Mounjaro?
Yes, but discuss specific supplements with your GP first. Mounjaro doesn't directly prevent vitamin absorption, but reduced food intake means targeted supplementation may help. Your prescriber can recommend which supplements suit your individual diet and health needs.
Do I need supplements if I'm on Mounjaro?
Not necessarily, but they may help if your food intake becomes very limited. Focus first on eating a balanced diet with protein-rich foods, vegetables, and whole grains. A multivitamin and B12 supplement are commonly recommended as supportive measures.
Is there a difference between Mounjaro and Wegovy for supplement needs?
Both are GLP-1-type medications (Mounjaro is dual GIP+GLP-1) that reduce appetite, so nutritional support is similar. Mounjaro's dual mechanism doesn't change supplementation needs. Individual requirements depend more on your eating patterns than which medication you take.
Will supplements affect my Mounjaro dose?
No, supplements don't typically affect Mounjaro dosing. However, always tell your prescriber about all supplements you take. Some may interact with other medications you're on, and your prescriber needs a complete picture of what you're consuming.
What's the best way to track my nutritional health on Mounjaro?
Eat nutrient-dense foods first, then supplement where gaps appear. Our free progress tracker helps you log your eating patterns and notice any nutritional trends. Your GP can also order blood tests to check vitamin levels if needed — particularly B12, iron, and vitamin D.
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.