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
Tirzepatide Dosing Schedule For Weight Loss In The UK
Tirzepatide is a prescription-only GIP and GLP-1 receptor agonist injection available in the UK for weight management in eligible adults. The drug is marketed as Mounjaro and comes as a weekly injection administered via KwikPen device. Understanding the tirzepatide dosing schedule is essential before starting treatment. This guide explains each dose level, the escalation timeline, and how the medication works to support weight loss alongside dietary changes and physical activity.
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.
Tirzepatide Dose Levels And Weekly Escalation Schedule
Tirzepatide is prescribed in a stepwise dose escalation over approximately 20 weeks, allowing your body to adjust and your prescriber to monitor response. Each dose is a once-weekly injection.
- 2.5 mg — Weeks 1–4 (initial/adjustment dose)
- 5 mg — Weeks 5–8+ (first maintenance dose)
- 7.5 mg — Weeks 9–12+ (escalation if needed)
- 10 mg — Weeks 13–16+ (escalation if needed)
- 12.5 mg — Weeks 17–20+ (escalation if needed)
- 15 mg — Week 21+ (maximum dose)
You must spend at least 4 weeks on each dose before escalating. Your prescriber may recommend staying on a lower dose if you experience significant side effects or achieve good results. Dose escalation is individualised based on tolerability and clinical response — not everyone progresses to the maximum dose.
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.
Expected Weight Loss And Practical Dosing Information
Clinical trial data (SURMOUNT-1) showed average weight loss of approximately 15% body weight at 5 mg, 19.5% at 10 mg, and 20.9% at 15 mg over 72 weeks alongside reduced-calorie diet and increased physical activity. Individual results vary significantly. Each KwikPen contains 4 weekly doses (approximately one month supply). You inject once per week on the same day. Rotate injection sites between stomach, upper thigh, and upper arm each week. Use our GLP-1 weight loss calculator to estimate potential outcomes at different tirzepatide doses based on your starting weight.
- 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 starting dose of tirzepatide for weight loss?
The starting dose is 2.5 mg once weekly for 4 weeks. This allows your body to adjust and minimises nausea and gastrointestinal side effects. Your prescriber will then escalate the dose every 4 weeks if tolerated.
How long does it take to reach the maximum tirzepatide dose?
It typically takes 20–21 weeks to reach the maximum 15 mg dose, assuming you escalate every 4 weeks without issues. Some people stay on lower doses (5 mg, 10 mg) if they achieve good results or prefer fewer side effects.
Can I skip doses or inject less frequently than weekly?
No. Tirzepatide must be injected once weekly as prescribed. The minimum time between doses is 72 hours (3 days). If you miss a dose by 4 days or less, inject it immediately and resume your normal schedule. If more than 4 days have passed, skip that dose and inject on your normal day.
Does tirzepatide work better at higher doses?
Clinical trials showed increasing weight loss from 5 mg to 15 mg, but individual response varies. Some people achieve meaningful results at lower doses (5–10 mg) and experience fewer side effects. Your prescriber will personalise your dose based on your results and tolerance.
How should I store tirzepatide pens between injections?
Unopened pens must be refrigerated at 2–8°C in the original carton. After first use, pens can be stored at room temperature (below 30°C) for up to 30 days. Never freeze. Dispose of the pen 30 days after first use, even if some doses remain.
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.