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
Weight Loss While Breastfeeding — Safe UK Guidance
Losing weight while breastfeeding is possible and often happens naturally, but it requires a careful, gradual approach to protect milk supply and your health. The NHS recommends waiting until breastfeeding is well-established (around 6–8 weeks postpartum) before actively trying to lose weight. Sustainable weight loss during lactation typically happens at around 0.5 kg per week, similar to general weight management guidance in the UK. It's important to maintain adequate nutrition and hydration, as your body has increased energy needs during breastfeeding. Always consult your GP or midwife before starting any weight loss programme while breastfeeding, as individual circumstances vary significantly.
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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.
How Weight Loss Works During Breastfeeding
Breastfeeding itself contributes to postpartum weight loss — producing milk burns approximately 300–500 extra calories per day, depending on how frequently you feed. Many women naturally lose weight during the first 6 months of breastfeeding without intentional dieting. However, aggressive calorie restriction (below 1,500 kcal/day) can reduce milk supply and affect milk quality, so gradual weight management strategies are not recommended.
Safe weight loss principles while breastfeeding:
- Eat a balanced diet with adequate protein, healthy fats, and complex carbohydrates
- Maintain a modest calorie deficit of around 300–500 kcal/day maximum
- Drink plenty of water — dehydration can reduce milk production
- Avoid very low carbohydrate diets, as carbs support milk production
- Wait until breastfeeding is stable before restricting calories
- Monitor milk supply and your baby's feeding patterns
Use our free BMI calculator to track your starting point and assess your healthy weight range, then establish realistic weight loss goals with your GP or health visitor.
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.
Medications and Breastfeeding — Important Considerations
If you're considering weight loss medication while breastfeeding, it's essential to know that most prescription weight loss injections are not recommended during breastfeeding. GLP-1 medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) have limited safety data in lactation and are not licensed for use while breastfeeding. These medications require clinical assessment by a GP or prescriber who can discuss your specific situation.
For safe, NHS-aligned weight management in the UK, focus on gradual lifestyle changes: balanced nutrition, regular physical activity (once you're cleared by your GP), and consistent monitoring. Many women find their weight naturally stabilises 6–12 months after stopping breastfeeding. Your GP can advise on the safest approach for your circumstances, especially if you have weight-related health concerns.
- 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.
When can I start trying to lose weight after having a baby while breastfeeding?
The NHS recommends waiting until breastfeeding is well-established, typically around 6–8 weeks postpartum, before actively trying to lose weight. Focus on nutrition and recovery during the early weeks. After this point, gradual weight loss of 0.5 kg per week alongside breastfeeding is generally safe for most women.
Can I use weight loss injections like Wegovy or Mounjaro while breastfeeding?
No — both Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only medications with limited safety data during breastfeeding and are not recommended by prescribers during lactation. Always discuss any weight management plans with your GP or midwife before starting.
How many extra calories does breastfeeding burn?
Breastfeeding typically burns approximately 300–500 extra calories per day, depending on milk supply and feeding frequency. This calorie expenditure contributes to natural postpartum weight loss for many women, even without intentional dieting.
What should I eat to lose weight safely while breastfeeding?
Focus on balanced meals with adequate protein, healthy fats, complex carbohydrates, fruits, and vegetables. Avoid very restrictive diets or low-carbohydrate approaches, as these can reduce milk supply. Drink plenty of water, eat regular meals, and maintain a modest calorie deficit of no more than 300–500 kcal per day.
Will breastfeeding help me lose pregnancy weight naturally?
Yes — many women lose weight naturally during the first 6 months of breastfeeding due to the calorie expenditure of milk production. However, weight loss varies by individual and is influenced by diet, activity level, genetics, and hormones. Use our free BMI calculator to track your progress and discuss realistic goals with your GP.
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.