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 When Pregnant?
No — Mounjaro (tirzepatide) is not recommended during pregnancy and should be stopped before conception. Both Mounjaro and Wegovy are prescription-only medications that have not been studied in pregnant women, and animal studies suggest potential risks to the developing baby. If you are planning to become pregnant or are already pregnant, your GP or prescriber must be informed immediately. This guide explains what you need to know about GLP-1 and GIP receptor agonists during pregnancy, and why clinical assessment with a healthcare professional is essential.
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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, Wegovy, and Pregnancy — What the Evidence Shows
Mounjaro (tirzepatide) is contraindicated in pregnancy. The UK product information and MHRA guidance clearly state that Mounjaro must not be used during pregnancy. Similarly, Wegovy (semaglutide), a GLP-1 receptor agonist, is also not recommended in pregnancy. Neither medication has been tested in pregnant women, and animal studies of tirzepatide have shown adverse effects on fetal development.
Both medications should be stopped at least one month before you plan to become pregnant. If you become pregnant while taking either medicine, contact your GP or prescriber immediately — do not stop the medication suddenly without medical guidance.
- Animal studies showed potential fetal harm with tirzepatide exposure
- No human pregnancy data available for either Mounjaro or Wegovy
- Both are classified as potentially harmful in pregnancy by regulatory bodies
- Oral contraceptive reliability may be affected by GLP-1 medications
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.
Pregnancy Planning and Weight Management — What Your GP Needs to Know
If you are taking Mounjaro or Wegovy and wish to become pregnant, discuss your plan with your GP or prescriber at least three to six months in advance. Your healthcare team can help you stop the medication safely and plan an alternative weight management strategy that is safe during pregnancy.
Pregnancy itself affects weight naturally — most women gain 10–12.5 kg (22–28 lbs) during pregnancy as part of healthy fetal development. Rather than using weight loss injections, pregnant women should focus on balanced nutrition, appropriate physical activity as advised by their midwife, and regular antenatal care. Your GP can assess whether you need additional support managing your weight during this time.
- 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'm trying to get pregnant?
No. Mounjaro should be stopped before you attempt to conceive. You should stop tirzepatide at least one month before starting to try for a baby. Discuss your pregnancy plans with your prescriber well in advance so they can help you transition to a safe weight management approach during this time.
What if I become pregnant while taking Mounjaro?
Contact your GP or prescriber immediately if you discover you are pregnant while taking Mounjaro. Do not stop the injection suddenly — your healthcare team will advise you on safe stopping. Early pregnancy medical support is important to check the health of your pregnancy.
Is Wegovy safer than Mounjaro during pregnancy?
No — both Mounjaro and Wegovy are contraindicated in pregnancy. Wegovy (semaglutide) is a GLP-1 receptor agonist, while Mounjaro is a dual GIP and GLP-1 receptor agonist. Neither has been studied in pregnant women, and both should be avoided during pregnancy and when planning conception.
Can I use the GLP-1 weight loss calculator while pregnant?
Our GLP-1 weight loss calculator is designed to project results with prescription weight loss medication — it is not suitable for use during pregnancy. If you are pregnant or planning pregnancy, discuss safe weight management with your GP or midwife instead of using weight loss medication.
What weight management options are safe during pregnancy?
During pregnancy, focus on balanced nutrition, regular antenatal appointments, and gentle physical activity as recommended by your midwife. Your GP can provide personalised dietary guidance. Weight loss injections like Mounjaro and Wegovy are not appropriate — healthy weight gain supports fetal development.
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.