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 Sleepiness — Cost and Access in the UK
Fatigue and sleepiness can occur when taking Mounjaro (tirzepatide), though it's not one of the most common reported side effects. If you're experiencing tiredness while on this prescription weight management injection, you'll want to understand whether this is temporary, how to manage it, and what your access options cost in the UK. This guide covers both NHS and private routes to getting Mounjaro, plus practical advice for managing sleepiness while using it.
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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.
UK Cost and Private Access Routes for Mounjaro
Mounjaro is available through two main routes in the UK: NHS specialist services and private online prescribing. Private prescription costs typically range from £150 to £320 per month depending on your dose, with each KwikPen containing four weekly injections. The starting dose (2.5 mg) is usually less expensive than higher maintenance doses (10–15 mg). When accessing privately, you'll have an online consultation with a UK-licensed prescriber who assesses your eligibility based on your BMI and health history before issuing a prescription to a GPhC-registered pharmacy. This route usually takes 24–48 hours from consultation to delivery. Use our free GLP-1 weight loss calculator to understand potential outcomes at different doses, which may help you discuss cost versus benefit with your prescriber.
- Private route: online assessment, rapid access, no NHS waiting lists
- Costs vary by dose and provider — shop around for best pricing
- Prescriptions valid at any UK pharmacy, not locked to one provider
- Initial consultation typically £20–£50 (sometimes included in first order)
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
NHS Access vs Private: Sleepiness and Long-Term Treatment
NHS access to Mounjaro is free at point of use but requires referral to a tier 3 specialist weight management service — your GP cannot prescribe it routinely. NICE (National Institute for Health and Care Excellence) has approved tirzepatide for use within NHS weight management services, but availability varies significantly across regions, and waiting lists can be months or years in many areas. If you experience sleepiness on Mounjaro through NHS services, your specialist team can adjust your dose or monitor whether the fatigue is dose-related or temporary. The advantage of NHS treatment is ongoing clinical support and monitoring; the disadvantage is access delays and limited choice of medication timing. Many people choose private prescribing for faster access, then switch to NHS if their GP practice later agrees to shared care arrangements.
- NHS: free but requires tier 3 referral and waiting list
- Private: paid but immediate access, direct prescriber contact
- Sleepiness often improves after first 2–4 weeks as your body adjusts
- Tell your prescriber promptly if fatigue affects daily function
- 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.
Does Mounjaro always cause sleepiness?
No. Fatigue appears in clinical trial data as a common side effect but affects fewer people than nausea or diarrhoea. Many users experience no sleepiness at all. If it does occur, it often improves within the first 2–4 weeks as your body adjusts to the medication.
How much does Mounjaro cost privately in the UK?
Private prescriptions typically cost £150–£320 per month depending on dose. Starting doses (2.5–5 mg) are usually cheaper than maximum doses (15 mg). Always check pricing across providers as costs vary. Consultation fees (£20–£50) may be added.
Can I get Mounjaro on the NHS in the UK?
Yes, but only through specialist tier 3 weight management services via referral from your GP. NICE approved it for NHS use, but availability and waiting times vary significantly by region. Contact your local ICB (Integrated Care Board) for eligibility and waiting times.
What should I do if Mounjaro makes me very sleepy?
Contact your prescriber promptly. Sleepiness may be dose-related, temporary, or linked to other factors. Your prescriber might adjust your dose, timing of injection, or diet. Never stop the injection without guidance. Our BMI calculator helps track whether your weight loss is progressing despite the fatigue.
Is sleepiness on Mounjaro permanent?
Usually not. Most people report fatigue improves within 2–4 weeks once their body adapts. However, individual experiences vary. If sleepiness persists beyond 4 weeks or worsens, inform your prescriber. It may require a dose adjustment or investigation of other contributing factors.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.