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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Does Mounjaro Affect Libido and Sexual Function?
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK. Some people have reported changes in sexual desire or function whilst taking it, though this is not listed as a common side effect in clinical trials. Sexual function can be affected by weight loss itself, hormonal changes, and overall health — making it difficult to isolate Mounjaro's direct effect. If you have concerns about libido whilst on tirzepatide, speak with your GP or the prescriber who issued your Mounjaro prescription. They can assess your individual situation and discuss whether changes might be related to the medication, weight loss, or other health factors.
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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 Weight Loss Medications May Affect Sexual Function
Sexual desire and function are influenced by multiple factors including physical health, hormonal balance, psychological wellbeing, relationship quality, and medications. Weight loss itself — whether achieved through diet, exercise, or medication — can paradoxically affect libido in different ways. Some people experience improved sexual confidence and function as they lose weight and feel better physically. Others report temporary changes in sexual desire during gradual weight management, possibly due to changes in hormone levels or energy availability.
With GLP-1 and GIP/GLP-1 medications like Mounjaro, research specifically investigating libido changes is limited. In the SURMOUNT clinical trials (which tested tirzepatide), sexual dysfunction was not reported as a common side effect. However, individual experiences vary. Some reported effects may relate to:
- Nausea or gastrointestinal discomfort reducing interest in intimacy
- Changes in energy levels or fatigue during dose adjustment
- Hormonal shifts associated with significant weight loss
- Psychological factors related to body image changes
These effects are typically temporary and improve as the body adjusts to the medication and stabilises at a new weight.
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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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What to Do If You Experience Changes in Sexual Function
If you notice changes in libido or sexual function after starting Mounjaro, discuss this with your prescriber or GP promptly — do not stop taking your medication without medical guidance. Your healthcare provider can help determine whether the change is related to tirzepatide, weight loss, other medications you may be taking, or unrelated health factors.
Keep a simple record of when changes began relative to your Mounjaro dose or weight loss progress. This information helps your GP understand the pattern. Sexual side effects from medications can sometimes be managed by adjusting timing of doses, switching to an alternative medication, or addressing underlying causes like depression or relationship stress. Remember that sexual function often improves as weight loss stabilises and your body adapts — many people find sexual confidence increases once they reach a comfortable, sustainable weight.
- 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 sexual dysfunction a common side effect of Mounjaro in the UK?
No. In the SURMOUNT clinical trials, sexual dysfunction was not listed as a common side effect of tirzepatide (Mounjaro). However, individual experiences vary. Any changes you notice should be discussed with your prescriber, as they may relate to weight loss, hormonal shifts, gastrointestinal side effects, or other factors rather than the medication directly.
Can losing weight on Mounjaro improve sexual function?
For some people, yes. Weight loss can improve physical health, confidence, and sexual function. However, others may experience temporary changes in libido during gradual weight management due to hormonal changes or energy shifts. These effects are usually temporary. Try our GLP-1 weight loss calculator to understand expected weight loss timelines and discuss any concerns with your GP.
Should I stop taking Mounjaro if it affects my libido?
No — do not stop Mounjaro without medical guidance. Always speak to your prescriber or GP first. They can assess whether changes are related to the medication or other factors, and explore options such as dose adjustment, timing changes, or alternative treatments if appropriate.
How long does it take for sexual side effects to resolve if they're medication-related?
If sexual changes are related to Mounjaro, they typically improve within a few weeks as your body adjusts to the medication and gastrointestinal side effects settle. However, timelines vary. Your GP can provide personalised advice and monitor your progress with regular follow-ups.
Is Mounjaro the same as Wegovy regarding effects on libido?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1-based medications, though Mounjaro is a dual GIP/GLP-1 agonist. Neither lists sexual dysfunction as a common side effect in clinical trials. Individual experiences may vary between the two. Your prescriber can discuss which medication may suit you best based on your health and any side effect concerns.
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