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 Thinning On Mounjaro — What You Need to Know
Hair thinning is listed as a common side effect of Mounjaro (tirzepatide), the prescription-only weight loss injection licensed in the UK. If you're considering Mounjaro or currently taking it, it's important to understand this potential side effect, why it happens, and when to seek advice from your GP. This guide explains what the evidence shows, who is most at risk, and what you can do if you experience hair loss while using this 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 Thinning and Mounjaro — What the Evidence Shows
Hair loss (alopecia) is classified as a common side effect of Mounjaro, meaning it may affect up to 1 in 10 people taking the medication. In clinical trials, hair thinning was reported by some participants, though it was not the most frequently reported side effect compared to nausea or digestive changes.
Why does Mounjaro cause hair thinning? The exact mechanism is not fully understood, but hair loss during gradual weight management is well-documented in medical literature. When your body loses weight quickly—especially at the rates seen with tirzepatide doses—it can trigger a condition called telogen effluvium. This is temporary hair shedding where hair follicles shift prematurely into a resting phase. The stress of significant weight loss, combined with changes in nutrient absorption and metabolism, can contribute to this effect. It is typically temporary and hair often regrows once weight stabilises or the medication is stopped.
- Hair loss may begin 2–3 months into treatment
- It is usually reversible when treatment stops or weight stabilises
- Severity varies widely between individuals
- Adequate protein and micronutrient intake may help reduce severity
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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 Thinning — NHS Guidance and Practical Steps
If you experience noticeable hair thinning while taking Mounjaro, speak to your GP or the healthcare professional managing your treatment. They can assess whether the hair loss is related to the medication and advise on next steps. Do not stop taking Mounjaro without medical guidance—your prescriber needs to manage any dose changes or discontinuation safely.
Practical steps that may help include: ensuring adequate protein intake (aim for 1.2–1.6g per kg of body weight during weight loss), taking a balanced multivitamin containing iron, zinc, and B vitamins, managing stress through gentle exercise or relaxation techniques, and avoiding harsh hair treatments. Using our free BMI calculator and progress tracker can help you monitor your overall weight loss rate—slower, more sustainable weight loss may reduce the severity of hair thinning. If hair loss persists beyond 3–6 months after stopping the medication, discuss this with your GP to rule out other causes.
- 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 thinning a permanent side effect of Mounjaro?
No, hair thinning caused by Mounjaro is usually temporary. Hair loss during gradual weight management (telogen effluvium) typically reverses within 3–6 months of stopping the medication or once weight stabilises. Individual timelines vary, but permanent hair loss from Mounjaro itself is not documented.
What should I do if I notice significant hair loss while taking Mounjaro?
Contact your GP or the healthcare professional prescribing your Mounjaro immediately. Do not stop the medication without medical advice. Your prescriber can assess whether the hair loss is medication-related and discuss options, which may include continuing at your current dose, slowing your dose escalation, or considering alternatives.
Does the Mounjaro KwikPen dose make a difference to hair thinning risk?
Hair thinning risk may be related to the speed and amount of weight loss rather than the specific dose of the Mounjaro KwikPen itself. Higher doses (10mg, 15mg) typically produce more weight loss, which could increase the risk. Slower dose titration—as recommended on NHS guidance—may reduce the severity of this side effect.
How does Mounjaro hair thinning compare to Wegovy?
Hair thinning is a reported side effect of both Mounjaro (tirzepatide) and Wegovy (semaglutide). Both medications cause gradual weight management, which can trigger telogen effluvium. The incidence appears similar between the two, though individual responses vary. Your prescriber can discuss which medication may suit your health profile best.
Can supplements help prevent hair thinning on Mounjaro?
While no supplement can assures prevention, maintaining adequate nutrition is important. Ensure you're getting enough protein, iron, zinc, and B vitamins—particularly important during gradual weight management. Discuss specific supplements with your GP or a registered dietitian before starting, as some may interact with medications.
Ready to take control of your weight loss journey?
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