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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Exercise Before Or After Eating: Does Timing Matter For Weight Loss?
Whether you exercise before or after eating has less impact on weight loss than total calorie balance and consistency. Both fasted and fed exercise can support weight management, though individual preference and energy levels vary. In the UK, prescription weight management options like Mounjaro and Wegovy are available alongside exercise and dietary changes for eligible adults. This guide covers exercise timing, plus UK-licensed medication options that may help with weight loss when used with increased physical activity.
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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.
UK Prescription Weight Loss Options: Mounjaro, Wegovy, and Saxenda
For UK adults managing weight loss, prescription medications are available through NHS specialist services or private prescribing. The three main UK-licensed options are:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, maximum dose 15 mg weekly. Clinical trials showed average weight loss of approximately 15–21% of body weight alongside reduced-calorie diet and increased physical activity.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, maximum dose 2.4 mg weekly. STEP trial data showed average weight loss around 14.9% body weight.
- Saxenda (liraglutide) — a GLP-1 receptor agonist delivered as a daily injection, maximum dose 3 mg daily. Evidence supports modest weight loss support when combined with lifestyle changes.
All three are prescription-only and require clinical assessment. Individual results vary significantly. These medications work best alongside regular physical activity—the type of exercise and timing is less critical than consistency and total volume.
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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.
NHS vs Private Access: How to Find Out If You're Eligible
NHS route: Weight loss injections are available through tier 3 specialist weight management services. Request a referral from your GP. Availability and waiting times vary significantly by region (ICB).
Private route: Available through UK-licensed online prescribers following clinical assessment. No NHS referral needed. Costs typically range from £129–£320 monthly depending on dose.
Eligibility: Adults with BMI 30+ (or 27+ with weight-related health conditions like type 2 diabetes, high blood pressure, or sleep apnoea) may be suitable. South Asian, Chinese, Black African, and Black Caribbean adults may be eligible at lower BMI thresholds. Your GP or licensed prescriber can assess whether prescription weight loss treatment is appropriate for you. Try our free GLP-1 weight loss calculator to explore potential outcomes, and use our BMI calculator to check your personal BMI as a starting point for conversation with your healthcare provider.
- 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 exercising before or after eating affect weight loss?
Timing has minimal impact on total weight loss. Weight loss depends on calorie balance, not when you exercise relative to food. Exercise on a full stomach may feel uncomfortable; exercising fasted or fed both work. Choose timing based on energy levels and comfort. Consistency matters far more than timing.
Can I take Mounjaro or Wegovy while exercising regularly?
Yes. Prescription weight loss medications work best alongside regular physical activity and dietary changes. Exercise is an important part of the weight management strategy. Inform your prescriber about your activity level during your assessment. Individual response varies.
How much weight can I expect to lose with prescription weight loss medication in the UK?
Clinical trials show average losses of 14–21% of body weight over 68–72 weeks, though individual results vary significantly. Results depend on the specific medication, dose, adherence, dietary changes, and physical activity. Your prescriber will discuss realistic expectations during assessment.
What is the difference between NHS and private weight loss medication in the UK?
Both NHS and private prescriptions dispense the same licensed medications (Mounjaro, Wegovy, Saxenda). NHS access is through specialist services (variable waiting times); private access is through online assessment. Medication quality and safety are identical. Availability and cost differ.
Should I talk to my GP before starting a weight loss injection?
Yes. If pursuing NHS access, ask for referral to specialist weight management services. If considering private access, a licensed prescriber will conduct a clinical assessment before issuing a prescription. Either route requires healthcare professional involvement to ensure safety and suitability for you.
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.