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
Is Mounjaro Safe During Pregnancy?
If you're taking Mounjaro and planning to become pregnant, or you've just discovered you're pregnant while on tirzepatide, it's crucial to speak with your GP immediately. Mounjaro is not recommended during pregnancy, and current evidence suggests it's safest to stop the injection before trying to conceive. This guide covers what you need to know about Mounjaro and pregnancy in the UK, including safety information, when to stop, and what weight management support is available during and after pregnancy.
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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.
What the Evidence Shows About Mounjaro and Pregnancy
Mounjaro (tirzepatide) is not licensed for use during pregnancy in the UK or anywhere globally. Animal studies have raised concerns about potential effects on fetal development, and there is insufficient human data to confirm safety. The manufacturer's guidance is clear: women should not become pregnant while using Mounjaro.
If you are planning to become pregnant, your GP or prescriber should discuss stopping Mounjaro well before conception. The MHRA (Medicines and Healthcare products Regulatory Agency) recommends that women of childbearing age using GLP-1 or GIP/GLP-1 medications should have reliable contraception in place — and if stopping contraception to try for pregnancy, Mounjaro should be discontinued first.
If you discover you are pregnant while taking Mounjaro: Stop the injection immediately and contact your GP or midwife. Do not take another dose. Your healthcare team will monitor your pregnancy closely and ensure appropriate support.
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.
Weight Management Support During and After Pregnancy
Pregnancy is not the time to lose weight, even if you're overweight or obese before conception. Instead, the NHS recommends aiming to maintain a stable weight during pregnancy, with gradual, modest weight gain appropriate to your pre-pregnancy BMI. Your GP and midwife can provide personalised guidance.
After pregnancy, once you've finished breastfeeding (if you choose to breastfeed), weight management options can be revisited with your GP. Mounjaro and other GLP-1 medications are not safe while breastfeeding, so an alternative approach — such as supported lifestyle changes or other medications safe in lactation — may be recommended. Your prescriber can assess your individual circumstances and discuss the best path forward for your health.
- 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.
How long before trying to become pregnant should I stop taking Mounjaro?
You should stop Mounjaro at least one menstrual cycle (approximately one month) before trying to conceive, though some prescribers recommend stopping 2–3 months prior to allow the medication to fully clear your system. Discuss timing with your GP or prescriber — they can give personalised advice based on your health.
What contraception should I use while taking Mounjaro?
The MHRA recommends reliable contraception while using Mounjaro. Barrier methods (condoms) or long-acting reversible contraception (LARC) such as IUDs, implants, or injections are suitable options. Mounjaro may reduce the absorption of oral contraceptive pills, so discuss alternatives with your GP or prescriber.
What should I do if I become pregnant while taking Mounjaro?
Stop your Mounjaro injection immediately and contact your GP, midwife, or maternity services without delay. Do not take another dose. Your healthcare team will arrange appropriate monitoring and support throughout your pregnancy. There is no evidence of harm from a single or few doses, but professional guidance is essential.
Is weight loss a priority during pregnancy if I'm overweight?
No. Pregnancy is not the time for intentional weight loss, regardless of your pre-pregnancy weight. The NHS recommends aiming for weight stability during pregnancy, with appropriate weight gain according to your BMI. After delivery and following breastfeeding (if applicable), weight management can be addressed with your GP's support.
Can I use Mounjaro again after pregnancy if I'm breastfeeding?
No — Mounjaro is not safe while breastfeeding. Once you've finished breastfeeding, you can discuss restarting Mounjaro or exploring other weight management options with your GP. Your prescriber will assess your individual circumstances and provide guidance on the safest approach.
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.