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 Long to Lose 5 Stone on Mounjaro in the UK?
There is no fixed timeline for losing 5 stone (63.5 kg) on Mounjaro, as results vary significantly between individuals. Clinical trials showed that on average, adults taking tirzepatide lost between 15% and 21% of their body weight over 72 weeks when used alongside a reduced-calorie diet and increased physical activity. For someone starting at 80 kg, this could mean losing around 12–17 kg — less than the 5 stone target. Your GP or prescriber can discuss realistic expectations based on your individual health and circumstances. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
NHS Eligibility and Mounjaro Prescribing in the UK
In the UK, Mounjaro (tirzepatide) is available through NHS specialist weight management services (tier 3) or privately through licensed prescribers. NHS access requires referral from your GP to a tier 3 multidisciplinary weight management service, though availability and waiting times vary significantly by region and integrated care board (ICB). The medicine is subject to MHRA additional monitoring (Black Triangle ▼ status) and must be prescribed following a clinical assessment.
- NHS eligibility: BMI of 30 or above, or 27–29.9 with weight-related health conditions (type 2 diabetes, hypertension, sleep apnoea, cardiovascular disease)
- Lower thresholds for certain groups: South Asian, Chinese, Black African, and Black Caribbean adults may qualify at BMI 27.5 or above due to higher metabolic risk
- Dose titration: Starting at 2.5 mg weekly, increasing to a maximum of 15 mg over 16+ weeks — each dose escalation requires at least 4 weeks at the current dose
- SURMOUNT trial data: At 15 mg weekly, average weight loss was approximately 20.9% body weight (roughly 16.7 kg from an 80 kg starting weight)
Individual results depend on starting weight, adherence to lifestyle changes, genetic factors, and metabolic response to the medication.
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 vs Private Routes and Realistic Timelines for 5 Stone Loss
If you aim to lose 5 stone (63.5 kg), this would require sustained weight loss of approximately 30–35% of body weight for someone starting at 160–180 kg — significantly higher than SURMOUNT trial averages. A more realistic NHS target is losing 15–20% of starting body weight, achievable over 12–18 months on a stable Mounjaro dose (usually 10 or 15 mg weekly) combined with dietary changes and physical activity. Private prescribers follow the same dose escalation timelines but may have shorter waiting times. Track your progress with our free progress tracker to monitor realistic milestones. If weight loss plateaus, your prescriber may adjust dose or explore additional lifestyle interventions. Always discuss your personal weight loss goals with your GP or specialist — they can provide individualised guidance based on your health status and comorbidities.
- 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 lose 5 stone on Mounjaro?
Possibly, but individual results vary widely. SURMOUNT trial data shows average weight loss of 15–21% body weight over 72 weeks on Mounjaro. For someone at 160 kg, this equates to roughly 24–33.6 kg (3.8–5.3 stone). Losing exactly 5 stone depends on starting weight, adherence to lifestyle changes, genetics, and metabolic response. Your GP can discuss realistic goals.
How long does it take to reach maximum Mounjaro dose?
Mounjaro requires gradual dose escalation over 16+ weeks. You start at 2.5 mg weekly, increasing by 2.5 mg every 4 weeks until reaching your effective dose (typically 10–15 mg weekly). Reaching 15 mg (maximum) takes at minimum 20 weeks if escalated every 4 weeks without pausing.
What if I'm not losing weight on Mounjaro?
Weight loss plateaus are common and can occur for several reasons: insufficient calorie deficit, medication tolerance, underlying metabolic conditions, or inadequate physical activity. Contact your prescriber — they may increase your dose (if not at maximum), review your diet and exercise, or investigate other health factors affecting weight loss.
Is Mounjaro available on the NHS for weight management?
Yes, Mounjaro is available through NHS tier 3 specialist weight management services following referral from your GP. Availability and waiting times vary by region. Private prescribing through licensed UK prescribers offers a faster alternative without NHS referral.
How does Mounjaro compare to other weight loss injections like Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist; Wegovy (semaglutide) is a GLP-1 agonist only. SURMOUNT trials showed Mounjaro achieved average weight loss of 20.9% at 15 mg versus approximately 14.9% for Wegovy at 2.4 mg. However, individual response varies, and your prescriber will recommend the most suitable option 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.