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
Does Mounjaro Increase Libido? What the Evidence Shows
Mounjaro (tirzepatide) is not known to increase libido, and sexual side effects are not listed as common effects in UK clinical trials or patient data. Like Wegovy (semaglutide), Mounjaro may indirectly affect sexual function through appetite suppression, nausea, or fatigue during the adjustment phase. Weight loss itself can sometimes improve sexual function and confidence over time. If you have concerns about sexual side effects from either medication, discuss them with your GP or prescriber — they can assess whether the medication is suitable for you or suggest alternatives.
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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.
Mounjaro vs Wegovy: Sexual Side Effects Comparison
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. Sexual dysfunction is not reported as a common side effect in SURMOUNT clinical trials, though individual experiences vary. Very common side effects include nausea, diarrhoea, and reduced appetite — these can indirectly affect mood and sexual function during the adjustment period.
Wegovy (semaglutide), a GLP-1 agonist only, shows a similar profile in STEP trials. Sexual side effects are not highlighted as expected effects. Both medications work by reducing appetite and slowing gastric emptying, which may cause temporary fatigue or nausea.
Importantly, weight loss achieved over time with either medication can improve sexual confidence, reduce joint pain, and support cardiovascular health — all factors that may positively influence sexual function. The dose titration approach (starting low and increasing gradually) allows your body to adapt, which may reduce early side effects.
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Individual Factors and Clinical Suitability
Sexual function is influenced by many factors: stress, relationship health, underlying medical conditions (diabetes, cardiovascular disease), medications, and self-confidence. Both Mounjaro and Wegovy may indirectly support sexual health by helping weight loss, reducing diabetes risk, and improving cardiovascular fitness.
However, early side effects like nausea or fatigue can temporarily reduce sexual interest. This typically improves as your body adjusts to the medication. Your prescriber will assess your full health picture during a clinical assessment to determine which medication (if either) is right for you. If sexual side effects do occur, they should be reported — your prescriber may adjust your dose or suggest an alternative.
- 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.
Does Mounjaro cause erectile dysfunction or low libido?
Sexual dysfunction is not reported as a common side effect of Mounjaro in clinical trials. Early side effects like nausea or fatigue may temporarily affect mood or interest, but these usually improve as your body adapts. If you experience sexual side effects, inform your prescriber immediately.
Is Wegovy better than Mounjaro for sexual function?
There is no evidence that Wegovy is superior to Mounjaro for sexual function. Both are GLP-1-based medications (Mounjaro is dual GIP+GLP-1) and neither lists sexual dysfunction as a common effect. Individual experiences vary, and prescriber suitability assessment is key.
Can weight loss from Mounjaro improve sexual function?
Yes, modest weight loss (5–10% of body weight) can improve confidence, reduce joint pain, and support cardiovascular health — all factors linked to better sexual function. However, this occurs over weeks to months, not immediately.
What should I do if I experience sexual side effects on Mounjaro?
Report it to your GP or prescriber immediately. They can assess whether it is a temporary adjustment effect, adjust your dose, or recommend an alternative medication. Do not stop the injection without medical guidance.
How do I know if Mounjaro or Wegovy is right for me?
A UK-licensed prescriber will assess your full health history, BMI, weight-related conditions, current medications, and any concerns during a clinical assessment. Use our GLP-1 weight loss calculator to explore potential outcomes, then discuss your options with your prescriber.
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.