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 Sex Drive in Women?
Sexual side effects, including changes to sex drive, are not listed as common or very common side effects of Mounjaro (tirzepatide) in the UK prescribing information. However, weight loss medications can indirectly affect sexual function through various mechanisms — including changes in energy levels, body confidence, and underlying health conditions. Both Mounjaro and Wegovy work through different mechanisms, which may influence side effect profiles differently. This guide compares what we know about both medications and how they may affect sexual health in women. Use our free GLP-1 weight loss calculator to explore how these medications might support your weight management goals.
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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: Mechanisms and Side Effect Profiles
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two separate hormone pathways in the body. This dual mechanism may result in a different side effect profile compared to single-mechanism medications. In clinical trials (SURMOUNT-1), the most common side effects were gastrointestinal: nausea, diarrhoea, vomiting, and constipation. Sexual dysfunction is not listed as a common side effect. Fatigue and decreased appetite were reported by some participants, which could indirectly affect libido through reduced energy levels.
Wegovy (semaglutide) is a GLP-1 receptor agonist only — it activates a single hormone pathway. In the STEP-1 clinical trial, similar gastrointestinal side effects dominated, with no sexual dysfunction reported as a common side effect. Some women reported fatigue, which similarly could reduce sexual interest indirectly.
Direct comparisons show that both medications have comparable side effect frequencies overall, though individual responses vary significantly. Neither medication is expected to directly suppress sexual function in the way some other medications (such as certain antidepressants) can.
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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How Weight Loss Medications Can Indirectly Affect Sexual Health
Changes to sex drive during weight management may stem from several indirect factors rather than the medication itself. Fatigue and nausea — particularly during dose titration or adjustment — can temporarily reduce sexual interest. As gastrointestinal symptoms typically settle over weeks or months, sexual interest often normalises. Body confidence improvements from weight loss often enhance sexual satisfaction and desire, counteracting any initial side effects. Improved health markers such as better blood sugar control, reduced joint pain, and improved energy can positively influence sexual function over time.
If you experience persistent changes to sex drive after starting Mounjaro or Wegovy, discuss this with your GP or prescriber. They can assess whether symptoms relate to the medication, dose, underlying health conditions, or other factors. Your prescriber may adjust your dose or suggest practical strategies to manage side effects. Calculate your BMI using our free tool to understand how weight affects your overall health baseline.
- 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 known side effect of Mounjaro in UK prescribing information?
No, sexual dysfunction is not listed as a common or very common side effect of Mounjaro. However, gastrointestinal side effects like nausea and fatigue may indirectly reduce sexual interest in some women, particularly during the initial weeks of treatment. These symptoms typically improve over time as the body adjusts to the medication.
Does Wegovy affect sex drive differently than Mounjaro?
Both Mounjaro and Wegovy have similar side effect profiles, with gastrointestinal symptoms being most common. Neither medication is known to directly suppress sexual function. Individual responses vary, and any changes to libido are more likely related to fatigue, nausea, or improved body confidence rather than direct hormonal effects on sexual desire.
Can weight loss improve sexual function while taking these medications?
Yes, sustained weight loss often improves sexual satisfaction and desire through multiple pathways: increased energy, better body confidence, improved cardiovascular health, and reduced joint pain. These positive changes may offset any initial fatigue or nausea experienced during dose titration, contributing to improved sexual health overall.
What should I do if I notice changes to my sex drive after starting Mounjaro?
Contact your GP or prescriber. Changes to libido can relate to nausea, fatigue, stress, or other factors — not necessarily the medication itself. Your prescriber can assess your individual situation, potentially adjust your dose, or suggest strategies to manage side effects while you continue treatment.
How do the dual mechanism of Mounjaro and single mechanism of Wegovy affect sexual side effects?
Mounjaro's dual GIP and GLP-1 action and Wegovy's single GLP-1 action both primarily affect appetite and blood sugar regulation. Neither mechanism directly targets sexual function. Clinical trials show comparable side effect profiles between both medications, suggesting mechanism differences do not significantly alter sexual side effects in most women.
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