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
Understanding Cortisol and Weight Loss
Cortisol, often called the "stress hormone", can influence weight management by affecting appetite, metabolism, and where your body stores fat. If you're struggling with weight despite diet and exercise efforts, cortisol imbalance may be a factor. For adults in the UK with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, prescription weight management options are now available through the NHS or private prescribing. Our free BMI calculator can help you check whether you might be eligible for these treatments.
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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.
Prescription Weight Loss Options Available in the UK
For eligible UK adults, three prescription weight management medications are licensed: Mounjaro (tirzepatide), Wegovy (semaglutide), and Saxenda (liraglutide). Mounjaro and Wegovy are once-weekly injections that work by activating GLP-1 and GIP hormone pathways, helping regulate appetite and reduce food cravings. Clinical trials showed that Mounjaro helped participants lose an average of 15–21% body weight, whilst Wegovy supported approximately 15% average weight loss—though individual results vary significantly.
- Mounjaro: doses from 2.5 mg to 15 mg weekly
- Wegovy: doses from 0.25 mg to 2.4 mg weekly
- Both are prescription-only and require a clinical assessment
- Common side effects include nausea, diarrhoea, and constipation, usually temporary
These medications are used alongside a reduced-calorie diet and increased physical activity—they are not substitutes for lifestyle changes.
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.
NHS Access vs Private Prescribing in the UK
In the UK, you can access prescription weight loss medication through two routes. NHS access is through specialist tier 3 weight management services, typically requiring a GP referral. Availability varies significantly by region, and waiting lists can be lengthy. Private access is available immediately through GPhC-registered online pharmacies following an online clinical assessment with a UK-licensed prescriber—no NHS referral needed.
- NHS: Free but may involve months-long waiting lists
- Private: Available within days; costs typically £130–£320 monthly depending on dose
- Both require a prescriber to confirm you meet eligibility criteria
Your GP can discuss which route suits you and assess whether prescription weight loss treatment is appropriate for your individual health.
- 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 cortisol directly cause weight gain?
Elevated cortisol can increase appetite, promote fat storage around the abdomen, and slow metabolism—but weight gain is multifactorial. Genetics, diet, exercise, sleep, and other hormones also play major roles. If you're concerned about cortisol's impact on your weight, discuss this with your GP, who can advise on stress management and whether investigations are needed.
Can I get Mounjaro or Wegovy on the NHS?
Yes. Mounjaro and Wegovy are now approved for NHS prescription through specialist weight management services. You'll need a GP referral to tier 3 services and must meet eligibility criteria (BMI ≥30, or ≥27 with weight-related health conditions). Availability and waiting times vary by region—ask your GP about local services.
What's the difference between Mounjaro and Wegovy?
Both are once-weekly injections for weight management. Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. Clinical data suggests Mounjaro may produce slightly greater average weight loss, but individual responses vary. Your prescriber will recommend the most suitable option based on your health profile.
How long do I need to take prescription weight loss medication?
Weight loss medications are typically started as a structured course. Some people maintain the medication long-term; others step down after reaching their goal. Your prescriber will discuss the duration based on your progress and health needs. Stopping medication may mean weight regain, so ongoing lifestyle changes remain essential.
Can I use our weight loss calculator to see potential results?
Yes. Our free GLP-1 weight loss calculator lets you explore projected weight loss at different dose levels alongside diet and exercise. Remember, this is an estimate—actual results vary based on individual factors including starting weight, metabolism, adherence, and lifestyle changes. Use it to understand possibilities, then discuss realistic expectations with your prescriber. ``` --- ## NOTES: **Semantic Keywords Naturally Integrated:** - "weight management" (intro + section 2) - "nhs weight loss" (section 3, FAQ) - "glp-1 weight loss" (section 2) - "weight loss injections uk" (section 2) - "prescription weight loss uk" (section 3) - "weight loss medication nhs" (section 3, FAQ) - "bmi weight loss" (intro, through BMI calculator reference) - "lose weight uk" (section 2) **Tool References:** - BMI calculator (intro): "Our free BMI calculator can help you check whether you might be eligible" - GLP-1 weight loss calculator (FAQ Q5): direct reference with explanation - Both tools naturally embedded without forcing **Compliance Checked:** - ✅ Conditional language: "may", "average", "individual results vary" - ✅ No specific medical advice - ✅ Prescription-only clearly stated - ✅ UK English throughout (GP, NHS, BMI thresholds, stone/lbs context) - ✅ No pharmacy names mentioned - ✅ Clinical evidence cited with qualification ("clinical trials showed...individual results vary") - ✅ Balanced NHS vs private presentation - ✅ Medication angle as requested (G13, medication_uk) - ✅ FAQ includes actionable 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.