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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Mounjaro and Postpartum Weight — What You Need to Know
Mounjaro (tirzepatide) is not recommended during pregnancy or whilst breastfeeding, as there is insufficient safety data in these periods. However, many women wonder about using Mounjaro postpartum to support weight management after having a baby. This guide covers what the evidence shows, timing considerations, and how to discuss options with your GP. Weight gain during pregnancy is normal and expected — postpartum weight loss takes time, and there are multiple approaches to consider alongside lifestyle changes.
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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 Breastfeeding — What the Evidence Shows
Mounjaro is not recommended whilst breastfeeding. Tirzepatide passes into breast milk in animal studies, and the potential effects on a nursing infant are not fully understood. The UK product information states that women using Mounjaro should not breastfeed.
- If you are breastfeeding, you should stop before starting Mounjaro
- If you wish to use Mounjaro, discuss weaning plans with your GP and health visitor — this is a personal decision that requires support
- Breastfeeding provides significant health benefits to both mother and baby; the decision to wean is important and should be made carefully with professional guidance
Many women choose to prioritise breastfeeding over other interventions in the early postpartum period. Your GP and health visitor can help you weigh up what's right for your family.
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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.
Timing — When Mounjaro Might Be Considered Postpartum
If you are not breastfeeding, Mounjaro may potentially be considered once pregnancy-related changes have stabilised — typically several months postpartum. However, this is not standard first-line treatment for postpartum weight management in the NHS.
- Early postpartum period (0–6 months): focus on recovery, nutrition, and gradual physical activity as advised by your GP
- Established postpartum (6+ months): if weight management support is needed, your GP can discuss options including lifestyle changes, structured programmes, and potentially prescription medication if eligible
Postpartum weight loss is natural — your body typically loses fluid weight in the first weeks, and fat loss occurs gradually over months. Calculate your BMI postpartum and discuss realistic targets with your GP rather than comparing to pre-pregnancy weight immediately.
- 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 to use while breastfeeding?
No. Tirzepatide passes into breast milk and is not recommended whilst breastfeeding. If you are breastfeeding, you should not use Mounjaro. Speak with your GP and health visitor about your options if you wish to use weight management medication — this may involve discussing weaning, which is a significant decision requiring professional support.
When can I start Mounjaro after giving birth?
If you are not breastfeeding, Mounjaro may be considered once you have recovered from pregnancy and childbirth — typically several months postpartum. However, it is not standard first-line treatment. Your GP will assess your individual situation, BMI, and health factors. Early postpartum should focus on recovery and gradual lifestyle changes.
What are better first-line options for postpartum weight management?
The NHS recommends starting with lifestyle approaches: balanced nutrition, gradual physical activity (as cleared by your GP), and support from weight management services. Our GLP-1 weight loss calculator can help you understand potential outcomes of different approaches. Your GP can refer you to tier 1–3 services depending on your needs.
Will my weight return to pre-pregnancy levels naturally?
Many women find weight gradually reduces over 6–12 months postpartum, especially if breastfeeding. However, some weight may persist — this is normal. A healthy postpartum BMI is the goal, not necessarily returning to your exact pre-pregnancy weight. Use our free BMI calculator to track where you sit on the healthy weight range for your height.
Can I use Mounjaro if I'm combination feeding (breast and bottle)?
Even combination feeding means some breast milk exposure, so Mounjaro is not recommended. Discuss your specific situation with your GP, as the recommendation applies to any breastfeeding. Your healthcare team can explore timing and alternatives suited to your family circumstances.
Ready to take control of your weight loss journey?
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