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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Weight Loss During Perimenopause — What You Need to Know
Weight gain during perimenopause is extremely common and frustrating for many women. Hormonal fluctuations — particularly changes in oestrogen, progesterone, and insulin sensitivity — make weight management more challenging during this life stage. Understanding why this happens and what strategies work best can help you take control of your health. This guide explains the science behind perimenopause weight gain and explores practical solutions, from lifestyle changes to prescription weight loss medication, all within the NHS and UK healthcare context.
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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 Weight Gain Happens During Perimenopause
Perimenopause is the transition phase leading to menopause, typically lasting 4–10 years. During this time, oestrogen and progesterone levels fluctuate dramatically, triggering multiple changes in your body:
- Slower metabolism: Declining oestrogen reduces how many calories your body burns at rest, meaning you need fewer calories to maintain the same weight
- Increased insulin resistance: Your cells become less responsive to insulin, making blood sugar control harder and fat storage — particularly around the abdomen — more likely
- Appetite changes: Hormonal shifts affect hunger hormones (ghrelin and leptin), often increasing appetite and cravings for sugary or high-fat foods
- Water retention: Progesterone fluctuations cause bloating and fluid retention, making the scales harder to predict week-to-week
- Muscle loss: Declining oestrogen accelerates muscle loss (sarcopenia), and muscle burns more calories than fat
On average, women gain 2–5 kg during perimenopause even without increased calorie intake. This is not a failure on your part — it is a predictable metabolic shift driven by hormones.
Clinically BackedWeight Loss
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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.
Practical Weight Management Strategies for Perimenopause
Sustainable weight loss during perimenopause combines dietary, exercise, and lifestyle approaches:
- Strength training 2–3 times weekly: Resistance exercise combats muscle loss, maintains metabolism, and improves bone density — critical during this life stage
- Adequate protein intake: Aim for 1.2–1.6 g per kg of body weight daily to preserve muscle and support satiety
- Regular cardiovascular activity: 150 minutes of moderate activity weekly helps insulin sensitivity and cardiovascular health
- Sleep and stress: Poor sleep and high cortisol worsen insulin resistance and weight gain — prioritise 7–9 hours nightly
- Use our free BMI calculator to track your personal weight health baseline, and monitor progress with our progress tracker to stay motivated through lifestyle changes
If lifestyle changes alone are not sufficient after 3–6 months of consistent effort, your GP can discuss further options.
- 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.
Does HRT (hormone replacement therapy) help with perimenopause weight loss?
HRT can help stabilise hormonal fluctuations and may ease some weight management challenges by improving insulin sensitivity and reducing appetite changes. However, some women experience modest weight gain on HRT initially. HRT is a personal decision — discuss benefits and risks with your GP. It is not primarily a weight loss treatment.
Can prescription weight loss medication help during perimenopause?
Yes. Women eligible for prescription weight loss medication (BMI ≥30 or ≥27 with weight-related health conditions) may benefit from GLP-1 weight loss injections. These work by reducing appetite and food cravings — effects that can help counter perimenopause-driven hunger changes. Your GP can assess eligibility and discuss whether this approach is right for you.
Why is weight loss harder during perimenopause than before?
Declining oestrogen reduces your resting metabolic rate by approximately 2–8%, meaning you burn fewer calories automatically. Combined with increased insulin resistance, appetite changes, and muscle loss, your body actively resists weight loss during this phase. This is metabolic, not motivational — it requires adjusted strategies.
How much weight is typical to gain during perimenopause?
Research shows the average weight gain during perimenopause is 2–5 kg over the entire transition period (4–10 years). However, individual variation is wide — some women gain more, some gain less. Using our BMI calculator can help you track your personal healthy weight range regardless of average figures.
Should I see my GP about perimenopause weight gain?
Yes — especially if weight gain is rapid (>0.5 kg per week), accompanied by other symptoms (irregular periods, hot flushes, mood changes), or if you have struggled to lose weight despite consistent effort. Your GP can rule out thyroid problems, discuss HRT, and explore weight loss options aligned with NHS guidance.
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.