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
Can You Take Mounjaro When Breastfeeding?
No, you should not take Mounjaro (tirzepatide) while breastfeeding. The UK product information clearly states that Mounjaro is not recommended for women who are breastfeeding. If you're breastfeeding and considering weight management treatment, it's essential to speak with your GP about safe alternatives. Your healthcare provider can discuss timing options, including waiting until breastfeeding has finished, or exploring other evidence-based weight loss approaches that are compatible with breastfeeding.
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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.
Why Mounjaro Is Not Recommended During Breastfeeding
Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist that is not licensed or recommended for use while breastfeeding. The medication's safety in breast milk has not been established, and it is unknown whether tirzepatide passes into breast milk or could affect a nursing infant.
The UK product information for Mounjaro clearly advises against use during breastfeeding as a precaution. This is a standard safety approach when a medication's effects on breastfed infants are not fully understood. Additionally, Mounjaro is prescribed as part of a weight management programme that typically requires reduced calorie intake and lifestyle changes—all factors that can be better managed once breastfeeding has finished.
If you are taking Mounjaro and become pregnant or plan to breastfeed, you should inform your prescriber immediately so they can review your treatment plan.
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.
What Are Your Options if You're Breastfeeding?
If you're interested in weight management while breastfeeding, discuss evidence-based approaches with your GP. These may include:
- A balanced, nutritious diet that supports milk supply
- Gradual physical activity as you recover postnatally
- Working with a registered dietitian for personalised guidance
- NHS-supported weight management services once breastfeeding has ended
Many women find that breastfeeding itself contributes to gradual weight loss over time. Once you've finished breastfeeding, you can explore prescription weight loss options like Mounjaro or Wegovy if clinically appropriate. Your GP can assess your individual circumstances and help you plan a safe, sustainable approach to weight management that aligns with your health goals and family 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.
Is tirzepatide safe while breastfeeding?
No. Tirzepatide (Mounjaro's active ingredient) is not recommended during breastfeeding because its safety in breast milk is unknown and effects on nursing infants have not been established. The UK product information advises against use while breastfeeding. Always inform your prescriber if you're breastfeeding.
When can I start Mounjaro after breastfeeding?
Once you've finished breastfeeding, you can discuss Mounjaro with your GP or a specialist weight management service. You'll need a clinical assessment to determine eligibility based on your BMI, health conditions, and overall health. There's no specific waiting period after breastfeeding ends.
Are there weight loss options while breastfeeding?
Prescription weight loss medications like Mounjaro are not suitable during breastfeeding. Instead, focus on balanced nutrition, gentle physical activity once cleared by your GP, and support from healthcare professionals. Breastfeeding itself can contribute to gradual weight loss over time.
What should I do if I'm taking Mounjaro and want to breastfeed?
Contact your prescriber immediately if you're taking Mounjaro and planning to become pregnant or breastfeed. They will advise you to stop treatment before conception or breastfeeding begins. Do not stop medication without professional guidance—discuss your plans with your healthcare team first.
How does Mounjaro compare to Wegovy for breastfeeding?
Neither Mounjaro nor Wegovy are recommended during breastfeeding. Both are GLP-1 or GIP/GLP-1 medications whose safety in breast milk is not established. Once breastfeeding has finished, your GP can assess which prescription weight loss option may be appropriate based on your individual health circumstances and NHS eligibility.
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.