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
Going Up To 5mg Mounjaro — What You Need To Know
Stepping up to the 5mg dose is a key milestone when starting Mounjaro (tirzepatide) in the UK. This is typically your first maintenance dose after the initial 2.5mg starter phase. Understanding what to expect — including potential side effects, how long to stay on this dose, and NHS prescribing context — helps you make informed decisions about your weight management journey. Our GLP-1 weight loss calculator can help you explore potential outcomes at different doses.
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.
Mounjaro 5mg Dose: UK Prescribing Pathway
The 5mg dose is typically reached during weeks 5–8 of Mounjaro treatment, following four weeks on the starting 2.5mg dose. This is the first maintenance dose — meaning many people will stay on 5mg for weeks or months, depending on their response and tolerability. According to NICE guidance and clinical trial data (SURMOUNT-1), average weight loss on 5mg is approximately 15% of body weight when combined with reduced-calorie diet and increased physical activity.
In NHS tier 3 specialist weight management services, progression to 5mg is determined by a healthcare professional based on your tolerance of the 2.5mg starter dose and your individual health profile. If you experienced significant side effects on 2.5mg, your prescriber may recommend staying on this dose longer or adjusting more slowly. The tirzepatide KwikPen device delivers a pre-filled 5mg dose — you cannot split doses.
- Typical timeline: weeks 5–8 (after four weeks on 2.5mg)
- Staying on 5mg: weeks to months, depending on response
- Next escalation: 7.5mg (if needed after minimum four weeks on 5mg)
- Clinical trial average: ~clinically studied weight loss at this 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.
Side Effects and Tolerability at 5mg
Most people experience some gastrointestinal side effects when escalating doses — nausea, diarrhoea, and constipation are very common in weeks 5–8. These typically ease within 1–2 weeks as your body adapts. Staying hydrated, eating smaller portions, and avoiding high-fat foods can help manage symptoms. If side effects are severe or persistent, inform your GP or specialist; they may recommend staying on 5mg longer before escalating further, or considering whether Mounjaro is right for you.
Use our free progress tracker to log your weight, symptoms, and how you feel weekly — this helps you and your healthcare team identify patterns and adjust your treatment plan confidently.
- 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 long should I stay on 5mg Mounjaro before increasing to 7.5mg?
MHRA guidance recommends a minimum of four weeks on each dose before escalating. Most people benefit from staying on 5mg for 4–8 weeks to allow their body to adapt and to assess whether this dose is producing the weight loss and tolerability they need. Your prescriber will guide you based on your individual response.
Will side effects get worse when I go up to 5mg?
Side effects may temporarily worsen during the first 1–2 weeks on 5mg — nausea, diarrhoea, and constipation are common. However, these typically settle as your body adjusts. If side effects are severe, contact your GP or prescriber; they can advise on symptom management strategies or adjust your treatment plan.
Can I get Mounjaro 5mg on the NHS in the UK?
Yes — Mounjaro is approved by NICE for use within NHS tier 3 specialist weight management services for eligible adults. Access varies by region and NHS ICB availability. Your GP can refer you to your local specialist service, though waiting lists can be lengthy. Private prescribing offers faster access without NHS referral.
What's the difference between Mounjaro 5mg and Wegovy for weight loss?
Mounjaro is a dual GIP and GLP-1 agonist; Wegovy is a GLP-1 agonist only. Clinical trials show Mounjaro may produce slightly greater average weight loss, though individual results vary significantly. Both are prescription-only and require clinical assessment. Your prescriber will recommend the most suitable option for you.
Should I use a BMI calculator to track my progress on 5mg?
Yes — use our free BMI calculator regularly to monitor changes in your BMI alongside your weight. This gives you a fuller picture of your health progress, especially when combined with waist measurements. Track these metrics weekly using our progress tracker to share with your GP or specialist.
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.