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 Cause Hair Loss? Mounjaro vs Wegovy
Hair loss is a reported side effect with Mounjaro and Wegovy, though it's not extremely common. Both weekly weight loss injections are GLP-1 or GLP-1/GIP medications licensed in the UK for weight management. Understanding how often hair loss occurs with each, why it happens, and what monitoring your prescriber provides is important when considering prescription weight loss treatment. This guide compares the clinical evidence and practical considerations for both medications.
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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.
Hair Loss Side Effects: Clinical Trial Data and Frequency
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. In the SURMOUNT-1 clinical trial, hair loss (alopecia) was reported as a common side effect, occurring in approximately 3% of participants at the 15 mg maintenance dose. Hair loss typically appeared during active weight loss phases and sometimes resolved after dose stabilisation.
Wegovy (semaglutide) is a GLP-1 receptor agonist only. In the STEP clinical trials, hair loss was less frequently reported compared to Mounjaro — occurring in around 1–2% of participants. The mechanism differs slightly because Wegovy works on a single pathway, whereas Mounjaro's dual action may affect hair growth cycles differently.
- Both are GLP-1-related effects (gradual weight management can trigger telogen effluvium)
- Hair loss typically occurs 2–3 months into treatment
- Most cases resolve within 3–6 months after stabilisation
- Individual variation is significant — not everyone experiences it
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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.
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Clinical Mechanism and Individual Suitability Assessment
Hair loss with weight loss injections is often related to gradual weight management triggering telogen effluvium — a temporary condition where hair follicles enter a resting phase and shed. The SURMOUNT trial data suggests Mounjaro's dual GIP/GLP-1 mechanism may carry slightly higher frequency than Wegovy's single GLP-1 pathway, though both are prescription-only and individual responses vary significantly.
Your prescriber will assess which medication suits your health profile during clinical assessment. If you have a personal or family history of hair loss, discuss this specifically — your GP or licensed prescriber can weigh the benefits of weight management against potential risks and monitor you accordingly. Using our GLP-1 weight loss calculator can help you understand projected outcomes, and tracking progress with our free progress tracker supports long-term monitoring.
- 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 hair loss with Mounjaro permanent?
No. Hair loss from weight loss injections is typically temporary telogen effluvium. Most cases resolve 3–6 months after weight stabilises. If hair loss persists beyond 6 months, contact your GP to rule out other causes like nutritional deficiency.
Which is safer — Mounjaro or Wegovy — for hair loss risk?
Wegovy shows slightly lower hair loss frequency (1–2%) in clinical trials compared to Mounjaro (3%). However, both are prescription-only and individual responses vary. Your prescriber will assess your specific health profile to determine suitability.
Can I prevent hair loss while taking Mounjaro or Wegovy?
Ensure adequate protein, iron, zinc, and vitamin D intake — nutritional deficiency worsens hair loss. Lose weight gradually where possible. Discuss preventive strategies with your GP or prescriber before starting treatment.
Should I avoid these medications if I have a family history of hair loss?
Not necessarily. Inform your prescriber about your family history during clinical assessment. They can monitor you more closely, discuss risk versus benefit, and recommend supportive measures. Hair loss risk alone doesn't exclude eligibility.
How do I monitor hair loss while on a weight loss injection?
Track shedding patterns (increased loss in shower or brush). Note timing relative to dose increases. Use our free progress tracker to monitor overall health markers. Report significant hair loss to your prescriber — they may adjust dosing or recommend nutritional support.
Ready to take control of your weight loss journey?
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