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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How Often Can You Inject Mounjaro — UK Dosing Schedule
Mounjaro (tirzepatide) is injected once every week, making it a convenient once-weekly treatment for weight management. Each pre-filled KwikPen contains four weekly doses, so one pen lasts exactly one month. Understanding the dosing schedule, how to access Mounjaro in the UK, and what it costs will help you decide whether this prescription medication is right for you. This guide covers UK-specific access routes, costs, and what to expect during the clinical assessment process.
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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.
Mounjaro Dosing Schedule and Injection Frequency
Mounjaro is administered as a once-weekly injection, with each dose delivered subcutaneously (under the skin) using a pre-filled KwikPen auto-injector device. The standard treatment begins at 2.5 mg and increases gradually over several weeks, reaching a maximum dose of 15 mg weekly.
- Week 1–4: 2.5 mg once per week (starting dose)
- Week 5–8: 5 mg once per week
- Week 9–12: 7.5 mg once per week
- Week 13–16: 10 mg once per week
- Week 17–20: 12.5 mg once per week
- Week 21+: 15 mg once per week (maintenance)
Each KwikPen contains exactly four weeks of doses, so one pen lasts one month. You inject on the same day each week, rotating injection sites between the abdomen, upper thigh, or upper arm. The dose titration (gradual increase) happens over approximately five months before reaching the maximum maintenance dose, though your prescriber may adjust this timeline based on your individual response and 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.
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Mounjaro Cost and UK Access Routes
In the UK, Mounjaro is available through two main routes: NHS specialist services and private prescription. NHS access is through tier 3 specialist weight management services following GP referral, though availability and waiting times vary significantly by region. Many areas have substantial waiting lists.
Private prescription costs typically range from £129 to £320 per month depending on the dose — lower doses cost less, higher doses cost more. This is obtained through an online clinical assessment with a UK-licensed prescriber, after which a prescription is issued and dispensed by a registered pharmacy. The assessment usually takes 24–48 hours, and medication is delivered within 2–5 working days. Both routes require a valid prescription; Mounjaro cannot be purchased without clinical assessment.
- 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.
How do I inject Mounjaro?
Mounjaro comes in a pre-filled KwikPen auto-injector. You inject once per week under the skin (subcutaneously) into your abdomen, upper thigh, or upper arm. Rotate injection sites weekly to prevent lipohypertrophy (localised fat thickening). The injection takes a few seconds and you can do it yourself at home.
What if I miss a Mounjaro injection?
If you miss a dose within 4 days of your scheduled injection, take it as soon as you remember, then resume your normal schedule the following week. If more than 4 days have passed, skip that dose and inject on your normally scheduled day. Never inject two doses within 72 hours.
How much does Mounjaro cost per month in the UK?
Private prescription costs typically range from £129 to £320 per month, depending on your dose. NHS access is free but requires specialist referral and varies by region. Use our GLP-1 weight loss calculator to estimate potential results at different doses, which may help inform your decision.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is approved by NICE for NHS specialist weight management services, but access is limited. You need a GP referral to tier 3 services, and availability varies by region. Many areas have lengthy waiting lists. Private prescription is an alternative if NHS access is delayed.
How do I store my Mounjaro KwikPen?
Unopened pens must be stored in a refrigerator at 2–8°C and kept in the original carton away from light. Once you start using a pen, it can be kept at room temperature (below 30°C) for up to 30 days. Discard 30 days after first use, even if medication remains.
Ready to take control of your weight loss journey?
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