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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What to Do If Mounjaro Isn't Working for You
If you're on Mounjaro and not seeing the weight loss results you expected, you're not alone—individual responses to GLP-1 and GIP/GLP-1 medications vary significantly. Some people find their current mounjaro kwikpen dose reaches a plateau, whilst others may need dose titration adjustments or a different medication approach entirely. This guide compares Mounjaro with Wegovy and explains why effectiveness differs, helping you understand your options and when to discuss alternatives 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.
Why Mounjaro Might Not Be Working as Expected
Several factors can affect how well Mounjaro works for you. Dose plateau is common—your body may adapt to your current mounjaro dose, reducing its effect over time. Lifestyle factors matter significantly: if calorie intake hasn't been reduced or physical activity hasn't increased, weight loss may stall regardless of medication.
Other reasons include:
- Medication adherence—missing doses or inconsistent injection timing affects results
- Undiagnosed medical conditions—thyroid problems, PCOS, or hormonal imbalances can interfere
- Certain medications—some drugs interact with GIP/GLP-1 agonists
- Metabolism differences—some people are naturally less responsive to tirzepatide
- Gastric issues—severe nausea or vomiting may limit food intake reduction benefits
Your prescriber can help identify the cause and adjust your mounjaro dose titration strategy or suggest alternatives.
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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
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Mounjaro vs Wegovy: Which Might Work Better for You?
If Mounjaro hasn't worked as expected, comparing it with Wegovy (semaglutide) may help you decide next steps. Both are once-weekly injections licensed in the UK, but they work differently. Mounjaro is a dual GIP and GLP-1 agonist—activating two hormone pathways simultaneously. Wegovy activates only the GLP-1 pathway. In clinical trials, Mounjaro showed slightly higher average weight loss (~20% body weight) versus Wegovy (~15%), but individual responses vary significantly.
Some people respond better to single-pathway activation (Wegovy), whilst others benefit from dual activation (Mounjaro). Switching between them requires prescriber guidance. Your mounjaro uk prescription status and eligibility for mounjaro nhs nice pathways may also influence your options—discuss all alternatives with your GP or specialist.
- 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.
Should I increase my Mounjaro dose if it's not working?
Only your prescriber should adjust your dose. Dose titration typically follows a structured schedule—minimum 4 weeks at each level before increasing. If you've plateaued, your prescriber may increase your dose, but they'll first check whether lifestyle changes, medication adherence, or other factors are responsible. Don't self-adjust.
How long does Mounjaro take to work?
Most people notice appetite reduction within days to weeks, but significant weight loss typically takes 8–12 weeks of consistent use at an effective dose. If you're not seeing changes after 12 weeks on a stable dose with proper diet and activity adjustments, discuss alternatives with your prescriber—you may benefit from dose increase or switching to Wegovy.
Can I switch from Mounjaro to Wegovy if Mounjaro isn't working?
Yes, switching is possible but requires prescriber guidance. Wegovy is a different medication with a different dosing schedule. Approximate dose equivalences exist (Mounjaro 15mg ≈ Wegovy 2.4mg), but your prescriber will determine the best transition plan. Some people respond better to single GLP-1 activation than dual activation.
Is Mounjaro available through NHS or private prescription in the UK?
Mounjaro is available through both NHS specialist weight management services (tier 3/4) and private online prescribing following clinical assessment. NHS access requires GP referral and varies by region. Private prescriptions are faster but involve out-of-pocket costs. Eligibility depends on BMI and health conditions—your GP can advise which route suits you.
What are common Mounjaro side effects that might affect weight loss?
Severe nausea, vomiting, and constipation can limit how much you eat, affecting weight loss progress. Appetite suppression is the intended effect, but if side effects are severe, your prescriber may adjust your dose or suggest gastroprotective strategies. Most side effects reduce as your body adapts, typically within 4–8 weeks per dose level.
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.