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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Hair Loss and Mounjaro — What You Need to Know
Hair loss (alopecia) is a reported side effect of Mounjaro (tirzepatide), the prescription weight loss injection available in the UK. If you're considering this weekly weight loss injection or already taking it, understanding this potential side effect is important. This guide explains what the evidence shows, when hair loss may occur, and what to do if you experience it. Always consult your GP if you have concerns about any side effects whilst taking Mounjaro or any prescription medication.
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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.
Hair Loss as a Mounjaro Side Effect — The Evidence
Hair loss is listed as a common side effect of Mounjaro, meaning it may affect up to 1 in 10 people taking the medication. In clinical trials, alopecia was reported by patients during weight loss treatment with tirzepatide. However, it's important to understand that not everyone experiences this, and when it does occur, it is often temporary and related to gradual weight management itself rather than the medication specifically.
- Hair loss typically occurs 2–3 months into treatment, coinciding with gradual weight management phase
- Weight loss triggers temporary hair shedding (telogen effluvium) — a normal physiological response to calorie deficit
- Most cases resolve within 6–12 months after starting treatment or stabilising weight
- Severe or prolonged hair loss should be reported to your GP or prescriber immediately
- Ensure adequate protein, iron, zinc, and B vitamins — nutritional deficiency worsens shedding
Hair loss during Mounjaro is not typically a reason to stop treatment, but your prescriber should be informed so they can assess whether the benefit outweighs this side effect for your individual situation.
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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.
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Managing Hair Loss — Practical Steps and NHS Support
If you experience hair loss whilst taking Mounjaro, several evidence-based strategies may help. Ensure your diet includes sufficient protein (aim for 1.2–1.6g per kg body weight), as gradual weight management on a calorie deficit can increase shedding if protein intake is inadequate. Include iron-rich foods, leafy greens, nuts, and seeds. A supplement containing biotin, zinc, and iron may support hair health, but discuss this with your GP first to avoid interactions.
Report hair loss to your prescriber or GP if it is severe, distressing, or persists beyond 12 months. They can assess whether continuing Mounjaro is right for you, consider dose adjustment, or recommend specialist dermatology input. Hair loss is not inevitable — many people take Mounjaro without significant shedding. Use our free GLP-1 weight loss calculator to understand expected weight loss timelines and discuss realistic outcomes with your healthcare provider.
- 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 common with Mounjaro?
Hair loss is a common side effect, affecting up to 1 in 10 people taking Mounjaro (tirzepatide). However, not everyone experiences it. When it does occur, it is often temporary and related to the gradual weight management itself rather than the medication. Most cases improve within 6–12 months.
When does hair loss usually start with Mounjaro?
Hair loss typically begins 2–3 months into treatment, when weight loss is most rapid. This timing suggests it is triggered by the calorie deficit and weight loss process (telogen effluvium) rather than a direct medication effect. Stabilising your weight can help reduce shedding.
Can I prevent hair loss whilst taking Mounjaro?
There is no assured way to prevent it, but maintaining adequate protein intake (1.2–1.6g per kg body weight), iron, zinc, and B vitamins may reduce severity. Ensure you are eating a nutritionally balanced reduced-calorie diet, not an extremely restrictive one. Discuss supplements with your GP before starting.
Should I stop taking Mounjaro if I experience hair loss?
Not necessarily. Hair loss is usually temporary and often resolves as your weight stabilises. However, inform your GP or prescriber immediately, especially if the shedding is severe or distressing. They can assess the benefit versus risk for you personally and consider alternatives if needed.
Is hair loss from Mounjaro permanent?
No. Hair loss associated with Mounjaro-induced weight loss (telogen effluvium) is almost always temporary. Hair regrowth typically begins within 3–6 months as weight stabilises and nutritional status improves. Permanent hair loss is rare and should be reviewed by your prescriber or a dermatologist.
Ready to take control of your weight loss journey?
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