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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Tirzepatide Doses for Weight Loss — What You Need to Know
Tirzepatide is a prescription-only weight loss injection available in the UK that works as a dual GIP and GLP-1 receptor agonist. If you're considering this medication, understanding the dose schedule is important. Tirzepatide dosing starts low and increases gradually over weeks to help your body adjust. This guide explains the UK dose progression, what each dose does, and what clinical evidence shows about weight loss outcomes. Always consult your GP or a licensed prescriber to determine if tirzepatide is suitable for you.
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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.
How Tirzepatide Doses Progress
Tirzepatide comes as a once-weekly injection in a pre-filled KwikPen device. The UK dosing schedule follows a structured escalation pattern to minimise side effects and help your body adapt. You start at 2.5 mg and increase every 4 weeks, provided you tolerate each dose.
- Weeks 1–4: 2.5 mg (starting/adjustment dose)
- Weeks 5–8: 5 mg (first maintenance dose)
- Weeks 9–12: 7.5 mg (escalation if needed)
- Weeks 13–16: 10 mg (escalation if needed)
- Weeks 17–20: 12.5 mg (escalation if needed)
- Weeks 21+: 15 mg (maximum dose)
Your prescriber may keep you on a lower dose if you experience significant side effects or achieve good results. There is no requirement to reach the maximum dose. Minimum time between dose increases is 4 weeks; you cannot increase more frequently than this.
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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.
Weight Loss Results by Dose — Clinical Evidence
Clinical trials (SURMOUNT-1) showed average weight loss results at different doses when combined with a reduced-calorie diet and increased physical activity. At 5 mg, participants lost approximately 15% of their body weight. At 10 mg, average loss increased to 19.5%, and at the maximum 15 mg dose, average loss was approximately 20.9% of body weight over 72 weeks.
Important: These are trial averages — individual results vary significantly. Some people achieve substantial weight loss at lower doses; others may need escalation to see meaningful results. Your prescriber will assess your progress and adjust your dose accordingly. Use our free GLP-1 weight loss calculator above to estimate potential weight loss at different 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.
Can I skip doses or take tirzepatide more frequently than once weekly?
No. Tirzepatide is designed as a once-weekly injection only. Missing a dose means waiting until your next scheduled injection day. If you miss a dose by more than 4 days, skip that dose and resume your normal weekly schedule. Never inject more frequently than once per week, and maintain at least 72 hours between injections.
What happens if I miss a dose of tirzepatide?
If you miss a dose within 4 days of when you should have taken it, inject as soon as you remember and continue your normal schedule the next week. If more than 4 days have passed, skip that dose entirely and take your next dose on the normal day. Always inform your prescriber if you miss multiple doses in a row.
Is there a difference between tirzepatide and semaglutide (Wegovy) doses?
Yes. Tirzepatide has a dual GIP and GLP-1 mechanism, while semaglutide (Wegovy) is a GLP-1-only agonist. Tirzepatide's starting dose is 2.5 mg; Wegovy starts at 0.25 mg. The maximum doses are also different — 15 mg for tirzepatide versus 2.4 mg for Wegovy. Results and dose schedules are not directly comparable; your prescriber will advise which is appropriate for you.
Can I adjust my tirzepatide dose myself?
No. Tirzepatide dosing must be managed by your prescriber. Only a licensed healthcare professional can assess your response, monitor side effects, and recommend dose increases or decreases. Contact your prescriber if you experience concerning side effects or feel you need a dose adjustment.
How long do I stay on each tirzepatide dose?
You remain on each dose for a minimum of 4 weeks before escalating. Your prescriber may keep you on a lower dose for longer if you're getting good results, experiencing side effects, or need more time to adapt. Some people stay on 5 mg or 7.5 mg long-term rather than reaching 15 mg. There's no fixed timeline — it depends on your individual response and health circumstances.
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.