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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Mounjaro And Hair Loss: What You Need To Know
Hair loss is a reported side effect of Mounjaro (tirzepatide), the prescription weight loss injection used in UK NHS and private weight management services. Though not everyone experiences it, hair thinning and alopecia are listed as common side effects in the clinical data. Understanding why this happens, how long it lasts, and when to seek GP advice can help you manage treatment effectively. This guide covers the key facts about Mounjaro and hair loss in a UK health context, plus what your healthcare team can do to support you.
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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.
Why Does Mounjaro Cause Hair Loss?
Hair loss during Mounjaro treatment is thought to occur due to several factors. gradual weight management itself can trigger telogen effluvium, a temporary condition where hair follicles shift into a resting phase and shed prematurely — this is well-documented across all significant weight loss scenarios. Additionally, Mounjaro causes reduced appetite and food intake, which may lead to nutritional deficiencies (particularly iron, zinc, and B vitamins) if diet is not carefully managed. These nutrients are essential for healthy hair growth. The dual GIP and GLP-1 mechanism of Mounjaro may also affect hormone balance, which influences hair cycling. Hair loss is listed as a common side effect affecting up to 1 in 10 people in clinical trials, though severity and duration vary. Most cases are temporary and improve once weight stabilises or medication is discontinued. If you're losing hair while taking this weekly weight loss injection, discuss it with your GP or prescriber to rule out other causes and ensure your diet includes adequate protein and micronutrients.
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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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Managing Hair Loss On Mounjaro: Practical Steps
If you experience hair loss while taking Mounjaro, several strategies may help. Prioritise nutrition: eat adequate protein (1.2–1.6g per kg body weight daily) and ensure your diet includes iron-rich foods, zinc sources, and B vitamins — consider a multivitamin after discussing with your GP. Stay hydrated and avoid very low-calorie intakes; aim for a sustainable deficit rather than extreme restriction. Hair care: use gentle shampoos, avoid tight hairstyles, and minimise heat styling. Most importantly, inform your prescriber if hair loss is severe or persistent. They can assess whether it's telogen effluvium (temporary), a nutritional issue (manageable), or warrants a dose adjustment or medication review. Track your overall progress using a progress tracker alongside monitoring hair changes — this helps identify patterns. Hair regrowth typically begins 3–6 months after weight stabilises.
- 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 a common side effect of Mounjaro in the UK?
Yes, hair loss (alopecia) is listed as a common side effect affecting up to 1 in 10 people taking Mounjaro. It's often temporary and linked to gradual weight management rather than the medication itself. Most cases improve once weight stabilises. Report persistent hair loss to your GP or prescriber.
How long does hair loss last when taking Mounjaro?
Hair loss from gradual weight management (telogen effluvium) typically lasts 3–6 months and resolves as weight stabilises. Some people see improvement within weeks of stopping the medication or slowing weight loss. Individual timelines vary — your GP can advise on your specific situation.
Can I prevent hair loss while taking Mounjaro?
Eat adequate protein and micronutrients (iron, zinc, B vitamins), stay hydrated, and avoid extreme calorie restriction — aim for gradual, sustainable weight loss. A balanced diet and gentle hair care may help. Discuss nutritional support with your GP or a registered dietitian.
Should I stop Mounjaro if I'm losing hair?
Don't stop without medical advice. Contact your GP or prescriber first — they can assess the cause, check for nutritional deficiencies, and discuss whether continuing is right for you. Hair loss may improve with dietary adjustments or a dose change.
When should I contact my GP about hair loss on Mounjaro?
Contact your GP if hair loss is sudden, severe, patchy, or accompanied by other symptoms like scalp pain or skin changes. Also seek advice if hair loss persists beyond 6 months or affects your wellbeing. Your GP can rule out other causes and review your treatment.
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