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 During Lactation — What's Safe?
Losing weight while breastfeeding requires careful consideration to maintain milk supply and protect your baby's health. The NHS recommends that lactating mothers do not attempt gradual weight management, as it can affect milk production and potentially release stored toxins into breast milk. A gradual approach with adequate nutrition is essential. This guide covers safe weight loss strategies during lactation, calorie requirements, and why prescription weight loss medications like Wegovy are not suitable during this time.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
Safe Weight Loss While Breastfeeding
The NHS advises that lactating mothers should aim for gradual weight loss of no more than 0.5 kg (1 lb) per week, and many experts recommend waiting until breastfeeding is established (at least 6 weeks postpartum) before attempting any weight management. gradual weight management can reduce milk supply and may concentrate toxins in breast milk.
- Minimum daily calorie intake during lactation: 1,800–2,000 kcal (plus additional calories for milk production)
- Breastfeeding burns approximately 300–500 kcal per day naturally
- A modest calorie deficit of 200–300 kcal per day is safer than 500 kcal per day
- Adequate protein, iron, and calcium are critical during lactation
- Dehydration can reduce milk supply — drink plenty of water
Any weight loss attempt must prioritise milk supply and nutritional adequacy. Your GP or health visitor can provide personalised guidance based on your individual 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.
Prescription Weight Loss Medications During Lactation
Prescription weight loss injections are not suitable during breastfeeding. Medications like Wegovy (semaglutide), a GLP-1 weight loss injection licensed in the UK, have not been studied in lactating women and may pass into breast milk. Similarly, Mounjaro (tirzepatide) is not recommended during lactation. The NHS advises stopping breastfeeding or delaying any prescription weight management treatment until breastfeeding is complete. After weaning, prescription weight loss medications can be considered following a clinical assessment with your GP. Focus on sustainable lifestyle changes—modest calorie reduction, balanced nutrition, and gradual physical activity—until lactation ends.
- 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 lose weight while breastfeeding?
Yes, but carefully and gradually. The NHS recommends waiting until breastfeeding is established (at least 6 weeks postpartum) and losing no more than 0.5 kg per week. gradual weight management can reduce milk supply and concentrate toxins in breast milk. Focus on balanced nutrition and a modest calorie deficit of 200–300 kcal per day rather than aggressive weight loss.
How many calories do I need while breastfeeding?
Lactating mothers typically need 1,800–2,000 kcal daily plus an additional 300–500 kcal for milk production (though breastfeeding itself burns these calories). Your exact needs depend on your body size, activity level, and milk supply. A health visitor or dietitian can provide personalised guidance to ensure adequate nutrition for you and your baby.
Can I use Wegovy or other weight loss injections while breastfeeding?
No. Prescription weight loss medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) are not recommended during lactation as they have not been studied in breastfeeding women and may pass into breast milk. The NHS advises completing breastfeeding before considering any prescription weight management treatment.
What's the safest way to lose weight while nursing?
Focus on a balanced diet rich in protein, fruits, vegetables, and wholegrains; stay well-hydrated; exercise gently (walking, postnatal yoga); and aim for gradual weight loss of 0.5 kg per week maximum. Avoid very low-calorie diets and "detox" programmes. Your GP or health visitor can monitor your progress and milk supply.
When can I consider weight loss medications after breastfeeding?
Once breastfeeding is complete, you can discuss weight management options with your GP. If you have a BMI of 30 or above (or 27+ with weight-related health conditions), you may be eligible for prescription weight loss treatment. A clinical assessment will determine whether medications like Wegovy or Mounjaro are appropriate for you, with guidance on safety and realistic expectations.
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.