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
Understanding the Mounjaro 5 Mg Injection Dose
The 5 mg dose is Mounjaro's first maintenance dose, typically started around week 5 after beginning a weekly weight loss injection course. At this strength, the tirzepatide injection may help support appetite reduction and weight management as part of a reduced-calorie diet and increased physical activity. This is a prescription-only medicine available in the UK following clinical assessment by a licensed prescriber. Individual results vary, and your GP or prescriber will monitor your response before considering any dose adjustments.
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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.
What Happens at the 5 Mg Mounjaro Dose?
The 5 mg Mounjaro injection is where most patients transition after completing the 2.5 mg starter dose (weeks 1–4). At this maintenance level, the dual GIP and GLP-1 receptor agonist mechanism is fully activated, potentially helping to regulate appetite signals and support feeling fuller after smaller meals. Clinical trial data from the SURMOUNT-1 study showed that participants at the 5 mg dose experienced an average weight loss of approximately 15% of their body weight over 72 weeks, though this was combined with reduced-calorie diet and increased physical activity.
- Onset: Effects typically continue to build as your body adjusts over weeks 5–8
- Side effects: Nausea, diarrhoea, constipation, and abdominal discomfort are common, especially in the first 2–4 weeks at this dose
- Injection: Once-weekly KwikPen injection, typically given on the same day each week
- Storage: Refrigerate unopened pens at 2–8°C; after first use, can be kept at room temperature for up to 30 days
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.
Dose Escalation and What Comes Next
Your prescriber will assess your response and tolerability at 5 mg before considering further escalation. The next step in dose titration is typically 7.5 mg (weeks 9–12), then 10 mg, 12.5 mg, and maximum 15 mg. You must spend at least 4 weeks on each dose before increasing. If you experience significant side effects at 5 mg, your prescriber may recommend staying at this dose longer or using additional support strategies. Use our GLP-1 weight loss calculator to estimate potential outcomes at different doses, and our BMI calculator to track where your weight sits within NHS healthy weight ranges throughout your treatment.
- 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 5 mg the standard Mounjaro dose for weight loss in the UK?
No — 5 mg is the first maintenance dose, not the standard. Most patients start at 2.5 mg (weeks 1–4), step up to 5 mg (weeks 5–8), then continue escalating. However, some patients stay at 5 mg if they experience good results or side effects become problematic. Your prescriber decides the best dose for you.
What's the difference between Mounjaro 5 mg and Wegovy for weight loss?
Mounjaro contains tirzepatide (dual GIP + GLP-1 agonist); Wegovy contains semaglutide (GLP-1 only). At 5 mg Mounjaro versus equivalent doses, Mounjaro's dual mechanism may produce slightly greater average weight loss, but individual results vary. Both are once-weekly injections prescribed following clinical assessment.
Will I definitely lose weight on the 5 mg Mounjaro dose?
Weight loss is not assured. Clinical trials showed average weight loss at this dose, but results vary significantly between individuals. Success depends on adhering to a reduced-calorie diet, increasing physical activity, and how your body responds to the medication.
What should I do if I have severe side effects at 5 mg?
Contact your prescriber or GP immediately. Do not skip doses or stop the injection without medical guidance. Your prescriber may recommend staying at 2.5 mg longer, managing side effects with dietary adjustments, or exploring other options — never self-adjust.
How long do I stay on the 5 mg Mounjaro dose?
Minimum 4 weeks, typically 4–8 weeks depending on your side effects and response. Your prescriber will decide whether to escalate to 7.5 mg or maintain at 5 mg. Treatment duration is individualised and depends on your health goals and GP recommendations.
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.