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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Can You Get Pregnant On Mounjaro?
If you're considering Mounjaro (tirzepatide) or currently taking it and planning a pregnancy, it's important to understand how this medication affects fertility and pregnancy safety. The short answer: Mounjaro is not recommended during pregnancy, and you should stop taking it if you become pregnant. However, current evidence suggests it may not permanently affect your ability to conceive. This guide covers what you need to know about Mounjaro and pregnancy in a UK context, including NHS guidance and practical steps for fertility planning.
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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 — What the Evidence Shows
Mounjaro (tirzepatide) is not recommended during pregnancy because safety data in pregnant women is limited. Animal studies have shown potential risks to the developing fetus, though human pregnancy data is sparse. If you become pregnant while taking Mounjaro, you should stop immediately and contact your GP or midwife. The good news: there is no evidence that Mounjaro permanently damages fertility or reduces your chances of conceiving in the future. Current medical guidance suggests that stopping the medication allows normal fertility to return. However, planning pregnancy while on Mounjaro requires discussion with your healthcare team. Your GP or fertility specialist can advise on timing — typically, stopping Mounjaro for a period before trying to conceive is recommended, though exact timelines vary individually. If you're taking Mounjaro as part of NHS tier 3 weight management services or privately, discuss pregnancy plans openly with your prescriber so they can support your transition safely.
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 and Mounjaro — Important Considerations
If you're taking Mounjaro and are sexually active but not planning pregnancy, reliable contraception is essential. One key interaction to know: oral contraceptives (the pill) may be less effective while taking Mounjaro. The medication slows gastric emptying and may reduce absorption of oral medications. The MHRA recommends that women using oral contraceptives add a barrier method (condoms) or switch to a non-oral form of contraception (such as the implant, coil, or injection) for 4 weeks after starting Mounjaro and for 4 weeks after each dose increase. This precaution ensures contraceptive reliability. If you're relying on the pill, discuss alternative contraception with your GP or sexual health clinic — they can recommend options that won't be affected by the dose titration process. This is a practical consideration worth sorting before beginning treatment.
- 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. Mounjaro is not recommended during pregnancy due to limited safety data in pregnant women. Animal studies have shown potential fetal risks. If you become pregnant while taking Mounjaro, stop immediately and contact your GP or midwife. You should discuss pregnancy planning with your prescriber before starting Mounjaro.
Will Mounjaro stop me from getting pregnant?
There is no evidence that Mounjaro permanently damages fertility or reduces your ability to conceive. Stopping the medication should allow normal fertility to return. However, most healthcare providers recommend planning a period of time off Mounjaro before attempting to conceive — discuss specific timing with your GP.
Does Mounjaro affect the contraceptive pill?
Yes, potentially. Mounjaro may reduce absorption of oral contraceptives, making the pill less effective. The MHRA recommends adding a barrier method (condoms) or switching to a non-oral form (implant, coil, injection) for 4 weeks after starting Mounjaro and after each dose increase. Speak to your GP about alternatives.
When should I stop Mounjaro if I want to become pregnant?
This is individual and depends on your circumstances. Discuss timing with your GP or fertility specialist — there is no single set period. Some guidance suggests stopping several weeks or months before attempting conception, but your healthcare team can advise based on your health, dose, and other factors.
What if I become pregnant while taking Mounjaro?
Stop taking Mounjaro immediately and contact your GP or midwife. Inform all healthcare providers that you were taking Mounjaro — this helps them monitor your pregnancy appropriately. Early pregnancy support is important, and your maternity team will manage any necessary adjustments.
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.