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
Does Mounjaro Affect Pregnancy?
Mounjaro (tirzepatide) is not recommended during pregnancy and should not be used if you are pregnant or planning to become pregnant. If you are considering Mounjaro treatment or are currently using it, it is essential to discuss pregnancy plans with your GP or prescriber. Women of childbearing age taking Mounjaro need additional contraception precautions. This guide covers NHS guidance on Mounjaro and pregnancy, including how to access specialist advice through NHS weight management services.
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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.
NHS Eligibility and Mounjaro in Pregnancy
Mounjaro is contraindicated in pregnancy — the MHRA (UK Medicines and Healthcare products Regulatory Authority) advises that tirzepatide should not be used during pregnancy or if you are planning to become pregnant. The medicine's effects on fetal development have not been fully studied in human pregnancies.
Women taking Mounjaro must use effective contraception. Additionally, the product information states that women should add a barrier contraceptive method or switch to a non-oral contraceptive for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase, as Mounjaro may reduce oral contraceptive absorption.
If you are a woman of childbearing potential eligible for Mounjaro through NHS specialist weight management services or private prescribing, your prescriber will discuss contraception requirements before treatment begins. If you become pregnant while taking Mounjaro, stop immediately and contact your GP.
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.
NHS vs Private Prescribing Access
Accessing Mounjaro through NHS specialist services means your care is managed by tier 3 or tier 4 weight management specialists who assess eligibility, prescribe the correct dose titration schedule using the Mounjaro KwikPen device, and monitor your progress. These services also provide contraception and pregnancy planning guidance as part of your care pathway.
Private prescribing via UK-licensed online prescribers also requires a clinical assessment. When comparing Mounjaro vs Wegovy (semaglutide) options, both require discussion of contraception and pregnancy plans. Always inform your prescriber of all relevant medical history, including fertility intentions, before treatment starts.
- 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.
Is Mounjaro safe during pregnancy?
No. The MHRA advises Mounjaro (tirzepatide) should not be used during pregnancy or if planning to become pregnant. Effects on fetal development are not fully established. If you become pregnant while taking Mounjaro, stop immediately and contact your GP or NHS weight management service for guidance.
What contraception is needed with Mounjaro?
Women taking Mounjaro must use effective contraception. Additional precautions are recommended: add a barrier method or switch to non-oral contraceptive for 4 weeks after starting Mounjaro and 4 weeks after each dose increase, as Mounjaro may reduce oral contraceptive absorption.
Can I take Mounjaro if I'm planning pregnancy?
No. If you are planning to become pregnant, inform your GP or prescriber. Mounjaro should be stopped before attempting pregnancy. Your prescriber can discuss safer alternatives or timing of treatment.
How do I access pregnancy-related advice on Mounjaro through the NHS?
Contact your GP, who can refer you to an NHS tier 3 specialist weight management service. Specialists will assess your eligibility, discuss Mounjaro dose titration, and provide contraception and pregnancy planning guidance as part of your treatment pathway.
Is Mounjaro safe for breastfeeding?
No. Mounjaro should not be used while breastfeeding, as it is not known whether tirzepatide passes into breast milk. Discuss safer weight management options with your GP or healthcare professional if you are breastfeeding.
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.