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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5mg Mounjaro Not Working — Understanding Dose and Timing
If you're on 5mg Mounjaro and not seeing weight loss results, you may still be in the early stages of treatment. The 5mg dose is typically a starting or adjustment dose, not a maintenance dose, and many people need to progress through higher doses to see significant results. Clinical trials showed that average weight loss increases substantially at higher doses — 10mg and 15mg — but individual responses vary. This guide explains what's normal, when to escalate, and how to discuss concerns with your prescriber.
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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 Mounjaro Dose Escalation Works in the UK
Mounjaro uses a gradual dose escalation schedule designed to help your body adjust and minimise side effects. The standard UK titration involves spending at least 4 weeks on each dose before increasing:
- Weeks 1–4: 2.5mg (starting dose)
- Weeks 5–8+: 5mg (first maintenance dose — where you are now)
- Weeks 9–12+: 7.5mg (if tolerated and needed)
- Weeks 13–16+: 10mg (escalation continues)
- Weeks 17–20+: 12.5mg
- Week 21+: 15mg (maximum dose)
If you've only been on 5mg for 4–8 weeks, you may not yet be at a dose where significant weight loss typically occurs. SURMOUNT clinical trial data showed that 5mg achieved approximately 15% average body weight loss, while 10mg achieved 19.5% and 15mg achieved 20.9% — meaning higher doses consistently showed better outcomes. Your tirzepatide response may improve substantially once your prescriber escalates your dose, provided you're tolerating the current dose well.
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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.
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When to Speak with Your Prescriber About 5mg Mounjaro
If you've been on 5mg for at least 4 weeks and experienced no weight loss whatsoever, or if you've had significant side effects preventing escalation, contact your prescriber. They will assess whether to increase your dose, continue at 5mg for longer to allow your body to adjust, or explore whether Mounjaro is the right fit for you.
Important factors your prescriber will consider: your actual weight loss (even modest loss counts), side effects you're experiencing, your adherence to reduced-calorie diet and increased physical activity, and any other health conditions. Use our free progress tracker to log your weight weekly — this gives your prescriber concrete data. Use our GLP-1 weight loss calculator to understand realistic projections at different doses based on clinical trial averages.
If you're struggling to access dose escalation through the NHS, remember that tier 3 specialist weight management services have significant regional variation in availability. Some areas have months-long waiting lists; others have faster access. If NHS escalation is delayed beyond reasonable timescales, discuss private prescribing options with your GP — a private prescriber can assess you and manage dose escalation more quickly if clinically appropriate. Both NHS and private routes require ongoing clinical oversight.
- 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 5mg Mounjaro supposed to cause weight loss?
5mg can cause weight loss — clinical trials showed approximately 15% average body weight loss at this dose — but it's typically a starting dose. Many people see better results at 10mg or 15mg. Individual responses vary significantly. If you've only been on 5mg for a few weeks, your prescriber may recommend continuing to allow your body to adjust before escalating.
How long should I wait before asking for a dose increase?
UK prescribing guidance recommends staying on each dose for at least 4 weeks before escalating. If you've reached this 4-week mark and have no weight loss or serious side effects preventing escalation, it's reasonable to discuss dose increase with your prescriber. They'll assess your individual situation and may move you to 7.5mg.
Could something else be wrong if Mounjaro isn't working?
Yes. Weight loss with Mounjaro depends on consistent adherence to a reduced-calorie diet and increased physical activity — the medication supports these changes but doesn't replace them. Your prescriber will also consider whether other health conditions, medications, or metabolic factors are affecting your response. They may suggest a structured weight management programme.
Is Mounjaro the same as Wegovy?
No. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, while Wegovy (semaglutide) is a GLP-1 agonist only. Both are UK-licensed for weight management and have similar weight loss profiles in clinical trials, but they work slightly differently. Your prescriber will advise if a switch is appropriate.
Should I stop taking Mounjaro if it's not working?
No — stop only on your prescriber's advice. Stopping abruptly doesn't help and means losing the benefit of any adjustment that's happening. Speak to your prescriber if you have concerns. They may escalate your dose, adjust your diet plan, check for underlying health issues, or explore alternatives if Mounjaro truly isn't suitable.
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.