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 Wegovy Safe During Pregnancy?
Wegovy (semaglutide) is not recommended during pregnancy, and you should stop taking it if you become pregnant. There is limited safety data on semaglutide use in pregnant people, and animal studies have shown potential risks to fetal development. If you are pregnant, planning to become pregnant, or breastfeeding, you should inform your prescriber immediately. Your GP can discuss safer weight management approaches during pregnancy and explore options after pregnancy or breastfeeding ends.
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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 Safety Data Shows
Wegovy is a GLP-1 receptor agonist — a prescription-only weight management injection licensed in the UK. Clinical trials and post-market data show limited information about use during pregnancy. Animal studies suggest potential risks including effects on fetal development, which is why Wegovy is contraindicated (not recommended) in pregnancy.
The UK Patient Information Leaflet for Wegovy explicitly states that the medicine should not be used during pregnancy. If you are taking Wegovy and discover you are pregnant, stop the injection immediately and contact your GP or midwife. They will monitor your health and discuss safe alternatives for weight management during pregnancy.
After pregnancy and breastfeeding ends, you can discuss restarting Wegovy with your prescriber following a new clinical assessment to ensure it remains appropriate for your circumstances.
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.
Planning Pregnancy and Contraception
If you are taking Wegovy and planning to become pregnant, discuss your plans with your prescriber at least 3 months in advance. You should stop Wegovy before trying to conceive. Use reliable contraception while taking Wegovy — the medicine may reduce the effectiveness of oral contraceptives (the pill).
If you are using the combined oral contraceptive pill, add a barrier method (condom) or switch to a non-hormonal contraceptive for 4 weeks after starting Wegovy and for 4 weeks after each dose increase. After stopping Wegovy, continue barrier contraception for a further 4 weeks before relying on oral contraception alone. Your GP or sexual health clinic can advise on the most reliable options for your circumstances.
Weight Management During PregnancyWeight management during pregnancy requires a different approach. The NHS recommends that pregnant people do not aim to lose weight, even if overweight or obese before pregnancy. Instead, focus on healthy eating and gentle physical activity as advised by your midwife.
Healthy weight gain in pregnancy varies but is typically 10–12.5 kg for adults with a pre-pregnancy BMI in the healthy range. Your midwife will monitor your health and that of your baby. After pregnancy, sustainable weight loss can be gradually addressed through diet, physical activity, and — if eligible and appropriate — prescription medication like Wegovy under medical supervision. Breastfeeding, if chosen, also supports gradual weight loss postnatally.
- 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 take Wegovy while trying to get pregnant?
No. Wegovy should be stopped before attempting to conceive. There is insufficient safety data in pregnancy. Stop at least 3 months before trying for a baby and discuss timing with your prescriber. Use reliable contraception while taking Wegovy, as it may reduce oral contraceptive effectiveness.
What if I become pregnant while taking Wegovy?
Stop the injection immediately and contact your GP or midwife. Do not take another dose. Inform your healthcare team so they can monitor your health and discuss safe weight management during pregnancy. Early notification allows proper antenatal care planning.
Does Wegovy affect fertility or conception?
There is no evidence that Wegovy directly affects fertility. However, it may reduce the effectiveness of oral contraceptives, so barrier methods are recommended. If you have concerns about fertility or conception, discuss these with your GP, who can arrange appropriate testing if needed.
Can I restart Wegovy after giving birth?
Yes. After pregnancy and breastfeeding (if applicable), you can discuss restarting Wegovy with your prescriber. A new clinical assessment will be needed to confirm eligibility based on your current BMI and health. Weight loss medication is typically introduced several weeks postpartum when your health has stabilised.
What weight management is safe during pregnancy?
Focus on healthy eating, prenatal vitamins, and gentle physical activity as advised by your midwife — not weight loss. The NHS recommends against intentional weight loss in pregnancy, even for obese individuals. After pregnancy, sustainable weight loss through lifestyle and (if eligible) prescription medication like Wegovy can be safely pursued.
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.