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 With Mounjaro — What You Need To Know
Hair loss (alopecia) is a reported side effect of Mounjaro that concerns many people starting this weight loss injection. While it's not assured to happen, it has been observed in clinical trials and real-world use. This guide explains why Mounjaro may cause hair loss, how common it is, and what options are available if you're experiencing this side effect. Always discuss any changes in your hair health with your GP or prescriber.
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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 Mounjaro May Cause Hair Loss
Hair loss associated with Mounjaro (tirzepatide) is thought to occur due to several interconnected factors. gradual weight management itself can trigger telogen effluvium — a temporary condition where hair follicles prematurely enter the shedding phase. Mounjaro is a dual GIP and GLP-1 receptor agonist, a weekly weight loss injection that produces significant weight loss over weeks. This accelerated fat and muscle loss can stress the body, including the hair growth cycle. Additionally, nutritional changes during weight loss may reduce intake of proteins, iron, zinc, and B vitamins — all critical for healthy hair growth. The dose titration process — starting at 2.5 mg and increasing to up to 15 mg weekly — may intensify metabolic stress. Hair loss reported in Mounjaro use is typically temporary and reversible once the body adapts, though individual timelines vary.
- Telogen effluvium is the most common cause — a stress-induced shedding phase
- Rapid metabolic changes can disrupt the hair growth cycle
- Nutritional deficiency during weight loss may contribute
- Hair loss is usually temporary but can last several months
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If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
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How Common Is Hair Loss With Mounjaro?
In clinical trials, alopecia (hair loss) was reported as a common side effect affecting up to 1 in 10 people taking Mounjaro. However, reported rates vary depending on dose and trial duration. Hair loss appears more frequently in individuals experiencing gradual weight management or those with existing nutritional vulnerabilities. The MHRA (Medicines and Healthcare products Regulatory Agency) monitors Mounjaro as a Black Triangle ▼ drug, meaning additional safety data is still being collected. If you're concerned about hair loss while taking Mounjaro, speak to your GP or the prescriber managing your prescription. They can assess whether the hair loss is related to the injection itself, to gradual weight management, or to underlying nutritional deficiency. Some patients find hair loss resolves within weeks once weight stabilises; others may need nutritional support or temporary pause in treatment.
- 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.
Can I prevent hair loss while taking Mounjaro?
While you cannot assures prevention, maintaining adequate protein intake (aim for 1.2–1.6g per kg body weight), taking a multivitamin containing iron and zinc, and staying well-hydrated may help support hair health during weight loss. Avoid crash dieting beyond the calorie deficit Mounjaro creates. Discuss nutritional strategies with your GP or a registered dietitian.
Is hair loss from Mounjaro permanent?
No. Hair loss from Mounjaro is typically telogen effluvium — a temporary shedding phase. Most people see regrowth within 3–6 months after the hair shedding stabilises, though individual timelines vary. If hair loss persists beyond 6 months, discuss this with your GP to rule out other causes.
Should I stop taking Mounjaro if I notice hair loss?
Do not stop Mounjaro without speaking to your prescriber first. Sudden cessation can cause other side effects. Your GP or prescriber can help you weigh the benefits of continued weight loss against the temporary hair loss, and discuss strategies to support hair health without stopping treatment.
What nutritional support helps with hair loss during Mounjaro?
Focus on protein (essential for hair structure), iron, zinc, B vitamins (especially biotin and B12), and vitamin D. A multivitamin designed for hair health may help. Discuss supplementation with your GP, particularly if you have existing deficiencies. Some people benefit from consulting a registered dietitian for a personalised plan.
Is hair loss more common with higher Mounjaro doses?
Hair loss risk may increase with higher doses (10 mg and above) as weight loss accelerates, though individual response varies. The dose titration schedule — increasing every 4 weeks — allows your body time to adjust. Your prescriber monitors your progress and can adjust your dose or support strategy if needed.
Ready to take control of your weight loss journey?
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