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?
Mounjaro (tirzepatide) is not recommended during pregnancy and should be stopped before trying to conceive. The NHS advises that women of reproductive age taking Mounjaro must use effective contraception and inform their prescriber if they plan pregnancy. This guidance prioritises the safety of both mother and baby. If you are pregnant, planning pregnancy, or breastfeeding, you must speak with your GP or healthcare provider before using Mounjaro or any other weight management medication. Your GP can discuss safer alternatives and provide personalised advice based on your individual health circumstances.
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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.
Mounjaro and Pregnancy: NHS Prescribing Guidance
Mounjaro is contraindicated in pregnancy — meaning it should not be used if you are pregnant or planning to become pregnant. The MHRA (UK medicines regulator) has classified tirzepatide as a medicine that may harm a developing baby, and animal studies suggest potential risks to fetal development.
If you are currently taking Mounjaro and discover you are pregnant:
- Stop taking Mounjaro immediately and contact your GP or midwife the same day
- Inform any healthcare provider you see (GP, midwife, hospital) that you have taken tirzepatide during early pregnancy
- Your medical team will assess individual risk and provide appropriate monitoring and support
- Do not panic — many medications are used in early pregnancy, and your healthcare team will advise on next steps
NHS specialist weight management services and prescribers have clear protocols for managing Mounjaro in women of reproductive age, including mandatory contraception and regular pregnancy risk assessments.
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.
Contraception, Fertility, and Family Planning
Effective contraception is essential while taking Mounjaro. The product information states that women of childbearing potential must use reliable contraception during treatment and for 8 weeks after the final dose.
- Oral contraceptives: Mounjaro may reduce their effectiveness by slowing gut absorption. Add a barrier method (condoms) or switch to a non-oral method for 4 weeks after starting and after each dose increase
- Long-acting reversible contraception (LARC): IUDs and implants are unaffected by Mounjaro and are ideal alternatives
- Fertility planning: If you plan to become pregnant, discuss stopping Mounjaro with your GP at least 8 weeks before trying to conceive to ensure it is fully cleared from your system
Always inform your prescriber of any contraception changes or pregnancy plans.
- 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 use Mounjaro if I am trying to get pregnant?
No. Mounjaro should be stopped before trying to conceive. Discuss timing with your GP or prescriber — you should wait at least 8 weeks after your final injection before attempting pregnancy to allow the medication to clear your system fully. Your GP can discuss safe weight management approaches during pregnancy planning.
What if I become pregnant while taking Mounjaro?
Stop taking Mounjaro immediately and contact your GP, midwife, or early pregnancy assessment unit the same day. Tell any healthcare provider you see that you have taken tirzepatide. Your medical team will assess your individual situation and provide appropriate support and monitoring. Early contact is important for safety planning.
Is Mounjaro safe while breastfeeding?
Mounjaro is not recommended during breastfeeding. It is not known whether tirzepatide passes into breast milk, but the MHRA advises against its use. If you are breastfeeding or planning to breastfeed, discuss alternative weight management options with your GP. Weight loss can often be achieved safely through diet and physical activity changes.
What are safe weight management options during pregnancy?
During pregnancy, weight loss medications like Mounjaro are not used. Instead, NHS guidance recommends healthy eating, staying active (as advised by your midwife), and gradual lifestyle changes. Most women should aim for modest weight gain in pregnancy rather than weight loss. Your midwife and GP can provide personalised advice.
Can I restart Mounjaro after pregnancy or breastfeeding?
Yes, Mounjaro can be restarted after breastfeeding has stopped. Discuss timing with your GP — they will assess whether you are eligible based on current BMI, health conditions, and your recovery postpartum. Your GP can also discuss whether other contraception options suit you better if restarting this medication.
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.