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 5mg — What You Need to Know
Tirzepatide 5mg is the first standard maintenance dose of Mounjaro, a prescription-only GLP-1 receptor agonist and GIP receptor agonist weight loss injection licensed in the UK. At this dose, clinical trials showed participants lost an average of approximately 15% of their body weight alongside a reduced-calorie diet and increased physical activity. This guide explains how tirzepatide works, UK eligibility criteria, what to expect at 5mg, and how it compares to other weight loss options. Always consult your GP or a licensed prescriber before starting any weight management medication, as individual results vary significantly.
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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.
How Tirzepatide 5mg Works and Dosing Schedule
Tirzepatide is a dual GLP-1 receptor agonist and GIP receptor agonist — a unique dual-action mechanism that sets it apart from other weekly weight loss injections like semaglutide (Wegovy). At 5mg, you've completed the initial titration phase and are now at the first maintenance dose. This dose is typically reached by week 5 of treatment, following a 2.5mg starting dose in weeks 1–4.
The dose escalates gradually: 2.5mg weeks 1–4, then 5mg weeks 5–8, with optional increases to 7.5mg, 10mg, 12.5mg, or maximum 15mg every 4 weeks if your prescriber determines it's appropriate. At 5mg, tirzepatide activates two natural appetite-regulating pathways in your body, helping reduce hunger cues, support feeling fuller after smaller meals, and slow gastric emptying. Unlike insulin, tirzepatide is not a diabetes medication — though it does help regulate blood sugar as a secondary benefit.
- Single once-weekly injection via KwikPen device
- Each pen contains 4 weekly doses (4 weeks supply)
- Administered into the stomach, thigh, or upper arm
- Can be stored at room temperature for up to 30 days after first use
- Prescription-only — requires clinical assessment before starting
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.
Eligibility, Expected Results, and Side Effects at 5mg
In the UK, you may be eligible for tirzepatide if you have a BMI of 30 or above, or BMI 27–29.9 with weight-related health conditions (type 2 diabetes, high blood pressure, or sleep apnoea). South Asian, Chinese, Black African, and Black Caribbean adults may qualify at lower BMI thresholds (27.5+) due to higher cardiovascular risk at lower weights.
At 5mg, clinical trial data from SURMOUNT-1 shows participants achieved an average of clinically studied weight loss over 72 weeks. Results vary considerably between individuals — some lose more, others less, and weight loss depends on consistent lifestyle changes alongside the injection. Common side effects at this dose include nausea, diarrhoea, constipation, and stomach discomfort — these typically ease after a few weeks as your body adjusts. Serious side effects are rare but seek urgent medical attention for severe persistent stomach pain (possible pancreatitis) or signs of allergic reaction. Use our GLP-1 weight loss calculator to estimate potential weight loss at different tirzepatide doses, and our BMI calculator to track your baseline and progress.
- 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.
Is tirzepatide 5mg the maximum dose?
No. 5mg is the first maintenance dose. Doses escalate up to 15mg maximum, increasing by 2.5mg every 4 weeks if your prescriber recommends it. Most people start at 5mg and may increase based on tolerance and response. Your prescriber will assess whether a higher dose is appropriate for you.
How much weight will I lose on tirzepatide 5mg?
Clinical trials showed an average of approximately clinically studied weight loss at 5mg over 72 weeks, alongside diet and exercise. Individual results vary significantly. Some people lose more, some less. Weight loss depends on adherence to lifestyle changes, not the injection alone. Use our free weight loss calculator to see projected outcomes based on your starting weight.
What's the difference between tirzepatide and semaglutide (Wegovy)?
Tirzepatide (Mounjaro) is a dual GLP-1 and GIP receptor agonist. Semaglutide (Wegovy) is a GLP-1 receptor agonist only. Tirzepatide's dual action may produce greater appetite suppression. Tirzepatide doses are also higher (up to 15mg vs Wegovy's 2.4mg maximum). Both are once-weekly injections, prescription-only, and require clinical assessment.
Can I get tirzepatide on the NHS?
Yes, tirzepatide is NICE-approved for NHS specialist weight management services (tier 3). However, NHS availability varies significantly by region and waiting lists can be lengthy. Private prescription is available without NHS referral through UK-licensed prescribers and GPhC-registered pharmacies.
What should I do if I miss a tirzepatide injection?
If you miss your 5mg dose, inject within 4 days of the scheduled date and resume your normal weekly schedule. If more than 4 days have passed, skip that dose and take your next injection on the usual day. Never take a double dose. Minimum spacing between injections is 72 hours (3 days).
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.