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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Couch to Five K Weight Loss — Prescription Medication Options in the UK
Starting a Couch to Five K running programme is an excellent way to build fitness and support sustainable weight loss. However, many people find that combining exercise with prescription weight management medication can accelerate progress and help maintain motivation. This guide covers the UK-licensed medication options available to eligible adults, how to access them through the NHS or private prescribing, and what the evidence shows about their effectiveness alongside physical activity.
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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.
UK-Licensed Prescription Weight Loss Medications
Three prescription medications are currently licensed in the UK for weight management and may be suitable for adults undertaking programmes like Couch to Five K:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist, taken as a once-weekly injection. In clinical trials, participants lost an average of 15–21% of their body weight over 72 weeks, though individual results vary significantly.
- Wegovy (semaglutide) — a GLP-1 receptor agonist, also once-weekly. STEP clinical trials showed average weight loss of approximately 15% body weight at the maximum dose.
- Saxenda (liraglutide) — a daily GLP-1 injection, with evidence for modest weight loss support. All three are prescription-only and require a clinical assessment before use.
Eligibility typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. These medications work by reducing appetite and helping you feel fuller after smaller meals — complementing the calorie deficit created by your Couch to Five K programme.
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.
Accessing Weight Loss Medication in the UK
NHS route: Your GP can refer you to a local tier 3 specialist weight management service, where a multidisciplinary team assesses your eligibility for prescription medication. NHS access varies significantly by region and waiting times can be lengthy in some areas.
Private route: Prescription weight loss medication is also available through online consultations with UK-licensed prescribers. Following a clinical assessment, eligible adults can have a prescription dispensed by a GPhC-registered pharmacy. Both routes require an individual clinical assessment — there is no self-referral or over-the-counter option.
Calculate your BMI using our free BMI calculator to understand where you currently stand, and discuss any weight management options with your GP as part of your overall health plan.
- 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 take weight loss medication while doing Couch to Five K?
Yes, prescription weight loss medication can be used alongside Couch to Five K, but should be discussed with your prescriber first. These medications reduce appetite and support calorie deficit — combining them with regular physical activity may help you progress faster. However, individual responses vary and your prescriber will advise whether it's appropriate for you.
What's the difference between Mounjaro and Wegovy for weight loss?
Both are once-weekly injections licensed for weight management in the UK. Mounjaro uses dual GIP and GLP-1 pathways and showed slightly higher average weight loss (15–21%) in trials compared to Wegovy (15%). Wegovy is a single GLP-1 mechanism. Individual results vary significantly, and your prescriber will assess which is more suitable based on your health profile.
How quickly will I lose weight with Couch to Five K plus medication?
The NHS recommends safe weight loss of 0.5–1 kg per week. Combining Couch to Five K with prescription medication may help you achieve this consistently, but results vary widely between individuals. Medication works best alongside sustained calorie deficit and physical activity — neither alone assures specific outcomes.
Do I need to be overweight to get prescription weight loss medication on the NHS?
NHS eligibility generally requires a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (such as type 2 diabetes, high blood pressure, or sleep apnoea). Lower BMI thresholds may apply if you're of South Asian, Chinese, Black African, or Black Caribbean heritage. Your GP can assess your individual eligibility.
What are the main side effects of weight loss injections?
Common side effects include nausea, diarrhoea, constipation, and stomach discomfort — these often improve over time. Serious side effects are rare but can include pancreatitis (severe stomach pain) or gallbladder issues. Your prescriber will discuss all potential side effects and monitor you during treatment. Always report unexpected symptoms to your healthcare provider.
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.