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
How Many Weeks Is Considered A Weight Loss Plateau?
A weight loss plateau is generally considered to have occurred after 4 to 6 weeks without any change on the scales, despite maintaining your calorie deficit or weight management approach. Plateaus are a completely normal part of weight management uk, and understanding what constitutes one helps you avoid unnecessary discouragement. Most people experience at least one plateau during their weight loss journey, and knowing the timeline helps you respond appropriately rather than abandoning your approach prematurely.
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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.
When Weight Loss Naturally Slows Down
As your body adapts to sustained weight loss, your metabolism adjusts and your body requires fewer calories to maintain your new weight. This is called metabolic adaptation. A weight loss plateau typically means no scale movement for 4–6 consecutive weeks, not a single week of stability. Some people define it more strictly as 6+ weeks of zero progress.
During the first 2–3 weeks of any new diet or weight management approach, your body sheds water weight alongside fat loss, which is why initial losses often appear rapid. Once this water weight stabilises (usually after week 3–4), the rate of loss naturally slows. This is normal and expected.
If you use prescription weight loss medication like GLP-1 weight loss injections, plateaus may occur as your body adjusts to the medication's effects over time. Your prescriber can advise whether dose adjustments are appropriate.
Use our free BMI calculator above to track how your BMI is changing, even if the scale feels static — sometimes body composition improvements happen before the scale moves again.
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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.
Why Plateaus Happen and What to Do
Plateaus occur due to metabolic adaptation, reduced energy expenditure from lower body weight, and hormonal adjustments. They're not a sign of failure — they're a sign your body is adapting.
Practical steps to break a plateau:
- Review your calorie intake — ensure you haven't gradually increased portions
- Increase physical activity intensity or duration
- Reassess your nhs weight loss progress over a longer timeframe (8–12 weeks rather than weekly)
- Check whether other metrics improved: clothing fit, energy levels, body measurements
- Ensure adequate sleep and manage stress, both affecting weight regulation
- Consider consulting your GP if plateau persists beyond 8–10 weeks
Our free progress tracker helps you log weekly weight and spot genuine plateaus versus natural weekly fluctuations caused by water retention, hormones, or meal timing.
- 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 2 weeks without weight loss a plateau?
No. A plateau typically requires 4–6 weeks of zero progress. Two weeks of stable weight is normal and doesn't indicate your approach isn't working. Weight naturally fluctuates week-to-week due to water retention, hormones, and digestion. Continue your current approach for at least 4 weeks before considering it a true plateau.
Can prescription weight loss medication like Wegovy cause plateaus?
Yes. Wegovy (semaglutide) is a GLP-1 injection that may help with weight loss, but your body can adapt to its effects over time. If you experience a plateau lasting 6+ weeks whilst on prescription weight loss uk medication, your prescriber may adjust your dose. Never adjust medication independently — always consult your prescriber.
How long does a weight loss plateau typically last?
Most plateaus last 2–4 weeks if you maintain your approach. Some last longer. The duration depends on factors including your current weight, metabolism, stress levels, sleep quality, and activity level. If a plateau lasts beyond 8–10 weeks, consult your GP for personalised advice rather than making drastic changes.
Should I eat less calories to break a plateau?
Not necessarily. Eating significantly fewer calories may trigger metabolic adaptation and muscle loss. Instead, try increasing physical activity, reviewing portion sizes to ensure you haven't drifted, improving sleep and stress management, or reassessing your bmi weight loss progress over a longer timeframe (12 weeks). Extreme calorie restriction should only be done under medical supervision.
Can I use the BMI calculator to track plateau progress?
Yes. Our free BMI calculator above shows whether your BMI is changing even if weight appears stable. Sometimes body composition shifts (losing fat whilst gaining muscle) before the scale moves. Tracking BMI alongside weight gives a fuller picture of your progress during a plateau.
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.