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?
There is no evidence that Mounjaro increases libido. In fact, some people taking this prescription weight management injection report changes in sexual desire or function, though these are not among the most commonly reported side effects. Weight loss itself can sometimes improve sexual function by reducing physical strain and boosting confidence, but Mounjaro is not known to enhance libido directly. If you have concerns about sexual function whilst taking Mounjaro, your GP can provide personalised advice.
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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.
What Does the Evidence Show?
Clinical trials of tirzepatide (Mounjaro's active ingredient) did not identify increased libido as a benefit or common side effect. The SURMOUNT-1 trial, which tested Mounjaro in over 2,600 adults, recorded nausea, diarrhoea, vomiting, and constipation as the most frequent side effects—but sexual function changes were not highlighted as a primary concern. Some people do report decreased libido or erectile dysfunction whilst taking GLP-1 or GIP/GLP-1 medications like Mounjaro, though this is not universal. These changes may be linked to overall health improvements, reduced appetite affecting energy levels, or individual hormonal responses. Weight loss itself often improves sexual confidence and reduces physical limitations, which can indirectly support sexual wellbeing. If you experience changes in libido on Mounjaro, discuss this with your GP—they may adjust your dose or explore whether other factors are involved.
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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.
When to Speak to Your GP
Any change in sexual function whilst taking a prescription medication warrants a conversation with your GP. Changes in libido can result from the medication itself, from weight loss, from changes in energy or mood, or from entirely unrelated health factors. Your GP can assess whether the change is temporary (many side effects settle within weeks), whether your Mounjaro dose needs adjustment, or whether another underlying condition may be responsible. Never stop taking Mounjaro without guidance from your prescriber. If you're considering starting this UK prescription-only weight management injection and have concerns about sexual function, raise these during your clinical assessment so your healthcare provider can monitor this carefully and discuss any individual risk factors.
- 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.
Can Mounjaro cause erectile dysfunction?
Erectile dysfunction is not a commonly reported side effect of Mounjaro in clinical trials. However, some individuals do experience changes in sexual function. This may relate to overall health changes, energy levels, or individual responses. Speak to your GP if you notice changes—they can assess whether adjustment is needed.
Does weight loss from Mounjaro improve sexual function?
Weight loss can indirectly improve sexual wellbeing by reducing physical strain, boosting confidence, and improving overall health. However, Mounjaro itself is not known to enhance libido. Individual experiences vary depending on personal health, relationships, and psychological factors.
Is low libido a common side effect of tirzepatide?
Low libido is not listed as a common side effect in Mounjaro clinical trials. Nausea, diarrhoea, and vomiting are far more frequent. Sexual function changes, if they occur, are typically individual responses rather than expected medication effects.
Should I stop Mounjaro if my libido changes?
Do not stop Mounjaro without speaking to your GP or prescriber first. Changes in sexual function may be temporary, related to dose adjustment, or linked to other factors. Your healthcare provider can help identify the cause and discuss options with you.
How does Mounjaro compare to Wegovy regarding sexual side effects?
Both Mounjaro and Wegovy are GLP-1 or GIP/GLP-1 agonists, and neither lists increased libido as a benefit. Clinical data shows no significant difference between them in terms of sexual function side effects. Individual experiences vary, and your GP can advise based on your medical history.
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.