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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What Is the Lowest Mounjaro Dose Available in the UK?
The lowest dose of Mounjaro (tirzepatide) available in the UK is 2.5 mg, used as a starting dose for the first 4 weeks of treatment. This initial dose allows your body to adjust to the medication before gradual escalation. Whether you're accessing Mounjaro through NHS specialist services or private prescribing, understanding how dosing works is important for managing expectations around weight loss and side effects. Our free GLP-1 weight loss calculator can help you explore potential outcomes at different dose levels alongside your prescriber's guidance.
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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.
Understanding Mounjaro Dose Escalation in the UK
Mounjaro dosing follows a structured escalation pattern designed to minimise side effects whilst optimising effectiveness. The 2.5 mg starting dose is held for 4 weeks before any increase. After this, doses typically escalate by 2.5 mg every 4 weeks: 5 mg (weeks 5–8), 7.5 mg (weeks 9–12), 10 mg (weeks 13–16), 12.5 mg (weeks 17–20), and up to the maximum 15 mg (week 21 onwards). Each KwikPen contains four weekly doses. This gradual titration approach—called dose titration—helps your body adapt and reduces nausea and gastrointestinal side effects that are common with faster escalation. Your prescriber may pause escalation or hold your current dose if you experience significant side effects. NHS specialist services and private prescribers both follow similar escalation protocols, though timing may vary based on individual tolerability.
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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 Access to Mounjaro in the UK
NHS access to Mounjaro is through tier 3 specialist weight management services, typically following GP referral. NICE has approved tirzepatide for use within NHS weight management pathways for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions. However, NHS availability varies significantly across regions—some ICBs have lengthy waiting lists, whilst others may have limited provision. Private prescribing is available through GPhC-registered pharmacies following an online clinical assessment with a UK-licensed prescriber, with no need for NHS referral. Costs vary by provider and dose but typically range from £129–£320 monthly. Both routes require clinical assessment to confirm eligibility and suitability; the lowest dose (2.5 mg) is standard regardless of access route.
- 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.
Why does Mounjaro start at such a low dose?
The 2.5 mg starting dose allows your body to adjust to the medication whilst minimising common side effects like nausea, vomiting, and diarrhoea. This lower initial dose improves tolerability and reduces the risk of people stopping treatment early due to adverse effects. Most prescribers will hold this dose for at least 4 weeks before escalating.
Will I lose weight on the lowest Mounjaro dose of 2.5 mg?
Weight loss typically becomes noticeable at higher doses (5 mg and above). The 2.5 mg dose is a tolerance and safety phase, not the therapeutic dose. Clinical trials showed most significant weight loss occurred at 10 mg and 15 mg doses. Individual results always vary, and weight loss should always be alongside a reduced-calorie diet and increased physical activity.
How long do I stay on 2.5 mg Mounjaro?
You remain on 2.5 mg for exactly 4 weeks (one KwikPen). After this initial 4-week period, your prescriber will typically escalate to 5 mg unless you're experiencing intolerable side effects. Escalation timing may be adjusted based on your individual tolerability and response.
Can I skip the 2.5 mg dose and start at a higher dose?
Starting at the lowest dose is standard practice across NHS and private prescribing in the UK to ensure safety and tolerability. Starting at a higher dose significantly increases the risk of severe nausea, vomiting, and gastrointestinal side effects, making treatment harder to tolerate. Your prescriber may recommend staying at a lower dose if you experience significant side effects, but skipping the initial dose is not advised.
What's the difference between Mounjaro's lowest dose and Wegovy's starting dose?
Mounjaro starts at 2.5 mg (once weekly), whilst Wegovy (semaglutide) starts at 0.25 mg (once weekly). Despite the numerical difference, these doses are not directly equivalent—they're based on different mechanisms (Mounjaro is dual GIP/GLP-1, Wegovy is GLP-1 only). Comparing Mounjaro vs Wegovy requires considering the full dose profile and individual response, not just the starting dose number.
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.