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 Until a Weight Loss Plateau?
A weight loss plateau is when your weight stays the same for several weeks despite continuing your diet and exercise routine. Most people experience a plateau after 4 to 6 weeks of initial weight loss, though this varies. It's a completely normal part of the weight management journey and doesn't mean your effort isn't working. Understanding why plateaus happen—and what to do about them—can help you stay motivated and achieve sustainable weight loss in the UK.
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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 Loss Plateaus Happen & UK Treatment Options
Weight loss plateaus occur when your body adapts to a reduced-calorie diet. As you lose weight, your metabolism adjusts and requires fewer calories to maintain your new body weight, slowing progress. After 4–6 weeks, many people notice weight loss slow significantly or stop entirely.
For eligible adults in the UK, prescription weight loss medication such as Mounjaro (tirzepatide) and Wegovy (semaglutide) may help break through a plateau. These GLP-1 medications work alongside diet and exercise to support continued weight loss by helping regulate appetite and food intake. NHS weight loss services and private prescribers both offer access to these options. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses if you're eligible for prescription treatment. Individual results vary, and a GP or prescriber will assess suitability based on your health.
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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.
Breaking Through Plateaus: NHS & Private Support Routes
If you're experiencing a weight loss plateau, several approaches can help. Adjust your calorie intake slightly or change your exercise routine to challenge your body differently. Increasing protein intake, staying hydrated, and ensuring adequate sleep all support continued progress.
In the UK, if you've been trying to lose weight without success, your GP can refer you to NHS weight management services (tier 3 specialists). For adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, prescription weight loss medication may be offered. Private prescribing is also available for eligible adults. Use our free BMI calculator to check your current status and discuss options with your GP. Weight loss is rarely linear—plateaus are temporary with the right support.
- 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.
What exactly is a weight loss plateau?
A weight loss plateau is when your weight remains stable for 2–4 weeks or longer despite maintaining your calorie deficit and exercise. It's not weight gain—your body is simply adjusting to your new lower weight. Plateaus are normal and typically temporary with continued effort.
How long do weight loss plateaus usually last?
Most plateaus last 2–4 weeks, though some can extend to 6–8 weeks. Duration varies based on factors like how much weight you've already lost, your metabolism, and whether you adjust your diet or exercise. Patience and consistency usually lead to innovative.
Can prescription weight loss medication help with a plateau?
Yes. If you're eligible, Mounjaro or Wegovy—both UK-licensed GLP-1 medications—may support continued weight loss when lifestyle changes alone have plateaued. These require a prescription following clinical assessment. Your GP or a licensed prescriber can determine eligibility based on your BMI and health.
Should I reduce calories further during a plateau?
Not drastically. Very low calorie diets (under 800 kcal/day) should only be done under medical supervision. Instead, try varying your exercise, increasing protein, or consulting your GP or NHS weight management service for personalised guidance tailored to your situation.
How can I tell if my plateau is normal or if I need help?
A 2–4 week plateau with no weight change is normal. If you've plateaued for 6+ weeks or are struggling to maintain motivation, speak to your GP. They can refer you to NHS weight management services or discuss prescription options like Mounjaro or Wegovy if appropriate.
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.