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
What Supplements Should I Take While On Mounjaro?
Taking supplements while on Mounjaro (tirzepatide) requires careful consideration, as some supplements may interact with this prescription-only weight management injection. Before starting any new supplements, you should always discuss them with your GP or the prescriber managing your Mounjaro treatment. This guide covers key information about supplement safety, absorption, and what to discuss with your healthcare team to ensure your supplementation plan works safely alongside your Mounjaro therapy.
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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 With Mounjaro
When taking Mounjaro, certain supplements become especially important due to how the medication affects digestion and nutrient absorption. Vitamin B12 is particularly relevant — GIP and GLP-1 receptor agonists like Mounjaro can affect how your body absorbs B vitamins, particularly B12, which is typically absorbed in the stomach. If you're experiencing nausea, vomiting, or reduced appetite on Mounjaro, your B12 intake may decline naturally through diet alone.
- B12 supplementation: Consider a B12 supplement or ask your GP about B12 monitoring, especially if you're on the medication long-term
- Multivitamins: A general multivitamin may help cover micronutrient gaps caused by reduced food intake
- Iron: If you experience fatigue alongside Mounjaro side effects, discuss iron levels with your GP — iron absorption can be affected by stomach acid changes
- Calcium and vitamin D: Important for bone health, particularly if weight loss is rapid
Always inform your prescriber of any supplements you're taking, as some may interact with Mounjaro or affect its efficacy.
Clinically BackedWeight Loss
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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 Avoid or Use With Caution
Certain supplements may not be suitable while taking Mounjaro. Herbal weight loss supplements and stimulant-based products should be avoided — combining them with Mounjaro increases the risk of side effects like nausea, diarrhoea, and stomach discomfort. Calcium supplements taken at the same time as oral medications may reduce absorption (a known effect of GLP-1 medications like Mounjaro).
- Space calcium supplements at least 2–4 hours apart from oral medications
- Avoid additional appetite suppressants or stimulant-based supplements
- Be cautious with very high-dose supplements that could strain the digestive system
- Discuss all herbal remedies with your GP, including ginger, turmeric, or digestive enzymes
Your prescriber can help you create a safe supplement plan tailored to your individual needs and Mounjaro dose.
- 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 multivitamin is generally safe with Mounjaro, but timing matters. Take it with a meal or as directed by the manufacturer. Some vitamins (especially fat-soluble vitamins like A, D, E, K) absorb better with food. Always mention your multivitamin to your GP or prescriber, as they may recommend adjustments based on your individual health.
Does Mounjaro affect vitamin absorption?
Yes. Mounjaro (tirzepatide) slows gastric emptying, which can affect how your digestive system absorbs nutrients. Additionally, reduced food intake due to appetite suppression may naturally lower your intake of certain vitamins and minerals. B12, iron, and calcium absorption may be particularly affected. Your GP can recommend monitoring or supplementation if needed.
Is it safe to take vitamin supplements while on Mounjaro with type 2 diabetes?
Yes, but supplements should be discussed with your GP, especially if you're also taking diabetes medications. Some supplements can affect blood sugar levels or interact with insulin or other diabetes drugs. Your prescriber will help you choose safe options that complement your Mounjaro treatment and diabetes management.
Should I avoid any specific supplements with Mounjaro?
Avoid weight loss supplements, herbal appetite suppressants, and high-dose stimulants (like excess caffeine supplements). Also be cautious with supplements claimed to "boost metabolism" or "burn fat," as these may increase nausea, dizziness, or digestive discomfort when combined with Mounjaro. Always check with your GP before starting anything new.
When should I take my supplements with Mounjaro?
Timing depends on the supplement type. Fat-soluble vitamins (A, D, E, K) absorb best with meals. B vitamins and water-soluble supplements can be taken independently. Calcium should be spaced 2–4 hours apart from other oral medications. Your prescriber or pharmacist can provide specific guidance based on your supplement routine and Mounjaro dose titration schedule.
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.