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?
Hair loss (alopecia) has been reported in some people taking Mounjaro, though it is not a common side effect. It typically occurs as a known but uncommon adverse reaction during weight loss treatment. Understanding what NHS guidance says about this potential side effect, how frequently it occurs, and what you can do if you experience it is important before starting this prescription weight loss injection. If you're considering Mounjaro as part of a weight management programme, knowing the full picture of possible side effects helps you make an informed decision with your GP.
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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 with Mounjaro — What NHS Data Shows
Hair loss with Mounjaro (tirzepatide) is classified as a common side effect — meaning it may affect up to 1 in 10 people taking the medication. In clinical trials, alopecia was reported during the SURMOUNT weight loss studies, though the exact mechanism is not fully understood. Hair loss can occur at any dose level and at any point during treatment, from early weeks to later in the course. The condition is typically reversible — most people experience regrowth after stopping Mounjaro or as the body adjusts to the medication. However, individual experiences vary significantly. Some people report no hair loss at all, whilst others experience noticeable thinning. Weight loss itself can contribute to temporary hair shedding (a condition called telogen effluvium), which makes it harder to isolate Mounjaro as the sole cause. NHS guidance recommends discussing any significant hair loss with your GP, who can assess whether it is related to the medication or other factors such as stress, nutritional deficiencies, or genetics. Your prescriber may recommend continuing treatment, adjusting your dose, or stopping the medication depending on the severity and impact on your wellbeing.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Managing Hair Loss — When to Seek GP Advice
If you notice increased hair shedding or thinning whilst taking Mounjaro, contact your GP or the healthcare professional managing your prescription weight loss treatment. Do not stop taking the medication without guidance. Your GP can assess whether the hair loss is related to Mounjaro, your gradual weight management, nutritional factors, or other causes. They may recommend nutritional support — ensuring adequate protein, iron, zinc, and B vitamins is important during weight loss and can support hair health. Keep a brief record of when hair loss started and how severe it is — this helps your healthcare team evaluate the situation. Many people find hair loss resolves within weeks to months after stopping Mounjaro or adjusting treatment. In the meantime, gentle hair care, avoiding heat styling, and managing stress can support hair health. If hair loss significantly affects your quality of life or wellbeing, discuss with your prescriber whether continuing Mounjaro remains appropriate for you.
- 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 serious side effect of Mounjaro?
Hair loss is a known but not serious side effect — it is reversible and typically resolves after stopping the medication or as your body adjusts. However, if it significantly impacts your wellbeing, discuss it with your GP. Most people experience regrowth over weeks to months.
How common is hair loss with Mounjaro?
Hair loss (alopecia) is classified as a common side effect, affecting up to 1 in 10 people. However, many people taking Mounjaro experience no hair loss at all. Individual experiences vary based on genetics, weight loss speed, and nutritional status.
Can I prevent hair loss whilst taking Mounjaro?
There is no assured way to prevent it, but maintaining adequate protein, iron, zinc, and B vitamins during treatment may help. Manage stress, avoid excessive heat styling, and be gentle with your hair. Discuss nutritional support with your GP if concerned.
Should I stop Mounjaro if I experience hair loss?
No — do not stop without talking to your prescriber first. Contact your GP or the healthcare professional managing your prescription weight loss treatment. They can assess severity and discuss whether continuing, adjusting the dose, or stopping is appropriate for you.
When does hair loss with Mounjaro typically start?
Hair loss can begin at any point during treatment, from early weeks onwards. It is often temporary and linked to gradual weight management (telogen effluvium), not Mounjaro directly. Most people see regrowth within weeks to months after treatment stops.
Ready to take control of your weight loss journey?
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