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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Low Dose Mounjaro in the UK: NHS Guidance and Starting Doses
Low dose Mounjaro refers to the initial 2.5mg and 5mg doses used when starting tirzepatide treatment in the UK. Mounjaro is a prescription-only, once-weekly injection that works as a dual GIP and GLP-1 receptor agonist. The NHS prescribes Mounjaro through specialist tier 3 weight management services for eligible adults. This guide explains UK starting doses, eligibility criteria under NICE guidance, and how the NHS manages initial treatment. Calculate your BMI using our free BMI calculator above to understand whether you may meet NHS eligibility thresholds for weight management support.
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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.
NHS Eligibility and Starting Dose Protocol for Mounjaro
In the UK, Mounjaro (tirzepatide) is initiated at 2.5mg once weekly, regardless of final target dose. This starting dose is continued for weeks 1–4 before a prescriber assesses tolerance and safety. After four weeks, the dose typically escalates to 5mg, then may increase further in 2.5mg increments up to the maximum 15mg dose. This gradual titration approach reduces nausea and stomach side effects that some people experience when starting GLP-1 and GIP agonists.
NHS eligibility for Mounjaro requires a BMI of 30kg/m² or above, or 27–29.9kg/m² with at least one weight-related health condition such as type 2 diabetes, high blood pressure, or cardiovascular disease. South Asian, Chinese, Black African, and Black Caribbean adults may qualify from a lower BMI threshold due to higher health risks at lower weights. Access is through NHS specialist weight management services following assessment by a consultant or specialist nurse — your GP can refer you to your local tier 3 service. NICE has approved tirzepatide for NHS use, though availability and waiting times vary significantly by region.
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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.
NHS vs Private Routes for Low Dose Mounjaro in the UK
NHS route: Free treatment through specialist weight management services, but typically involves a waiting list (in some areas, months to over a year). Your GP refers you to your local ICB tier 3 service. Once assessed, you receive a prescription and ongoing monitoring. Private route: Available through GPhC-registered online services with UK-licensed prescribers following an online clinical assessment. Private Mounjaro costs vary (approximately £129–£320 monthly depending on dose) but you can start within days without NHS referral. Both routes require the same starting protocol: 2.5mg weekly, dose reviewed after 4 weeks. Consider using our GLP-1 weight loss calculator to estimate potential outcomes. Your choice between NHS and private depends on urgency, cost, and local NHS availability.
- 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 is the lowest dose of Mounjaro available in the UK?
The lowest dose is 2.5mg, used as the starting dose for all UK patients. It is injected once weekly and continued for 4 weeks before potential escalation. This gradual start helps your body adjust and reduces early side effects.
How long do you stay on 2.5mg Mounjaro?
You remain on 2.5mg Mounjaro for weeks 1–4 (one month). At week 5, your prescriber reviews your response and side effects. If well tolerated, you typically escalate to 5mg. The dose can only increase once every 4 weeks minimum.
Can you get low dose Mounjaro on the NHS?
Yes. Mounjaro is NICE-approved for NHS weight management services. You must be referred by your GP to your local tier 3 specialist service. Eligibility requires BMI ≥30 or ≥27 with weight-related health conditions. Waiting times vary by region—some areas have significant delays.
What is the difference between Mounjaro and Wegovy starting doses?
Mounjaro starts at 2.5mg weekly. Wegovy (semaglutide) starts at 0.25mg weekly. Mounjaro is a dual GIP+GLP-1 agonist; Wegovy is a single GLP-1 agonist. Both use gradual dose escalation, but Mounjaro's starting dose is higher and has a steeper titration schedule.
Should I expect weight loss on the low dose Mounjaro?
Weight loss on 2.5mg is typically modest—clinical data suggests most significant loss occurs at higher doses (10mg–15mg). You may notice reduced appetite or smaller portion sizes. Track your progress using our free progress tracker, and discuss expectations with your prescriber.
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.