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
Free tracker included with every download this week
Mounjaro Exhaustion: Cost and Access in the UK
Mounjaro (tirzepatide) is a prescription-only weight management injection that can cause tiredness or low energy as a side effect. If you're experiencing exhaustion on Mounjaro, understanding how to access the medication, manage costs, and get support from your prescriber is essential. This guide covers UK pricing, NHS access routes, and private prescription options to help you make informed decisions about your weight management journey.
10,000+ calculations today · NHS-aligned thresholds · 100% free
Calculate Your BMI Instantly
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 Access Routes for Mounjaro
Accessing Mounjaro in the UK involves two main pathways: NHS specialist services or private prescription through an online prescriber. NHS access is typically through tier 3 or tier 4 weight management services following a GP referral, though waiting lists vary significantly by region and availability can be limited. Private prescription costs generally range from £130–£350 per month depending on your dose, as each KwikPen contains 4 weekly doses. The dose titration schedule—starting at 2.5 mg and increasing gradually to your maintenance dose—means initial months may cost less than later stages when on higher doses like 10 mg or 15 mg. When comparing Mounjaro vs Wegovy, Mounjaro's higher maximum dose (15 mg) often comes at a higher cost than Wegovy's maximum (2.4 mg), though both require a clinical assessment before prescription. Private prescribers assess your eligibility based on BMI and health conditions, similar to Mounjaro NHS NICE guidance criteria, ensuring treatment is appropriate for your individual circumstances.
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.
Exhaustion on Mounjaro and Accessing Support
Fatigue and exhaustion are common side effects when starting Mounjaro or increasing your dose—this often improves over time as your body adjusts. If you're experiencing persistent tiredness, contact your prescriber before your next dose, as they may recommend staying on your current dose longer or adjusting your dose schedule. Your prescriber can also rule out other causes like dehydration, inadequate calorie intake, or anaemia. Both NHS and private prescribers provide ongoing support, though private online consultations may offer faster response times. Use our free BMI calculator to monitor your health progress, and our GLP-1 weight loss calculator to review expected outcomes at your current dose—understanding what to expect can help you distinguish normal adjustment from concerning symptoms.
- 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.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £130–£350 per month depending on your dose. Each KwikPen contains 4 weekly doses. Starting doses (2.5 mg) may cost less than higher maintenance doses. Prices vary between prescribers, so it's worth checking current costs before starting treatment.
Can I get Mounjaro on the NHS in the UK?
Yes, Mounjaro is available through NHS specialist weight management services (tier 3/4) if you meet eligibility criteria: BMI 30+ or 27+ with weight-related health conditions. You'll need a GP referral, and waiting lists vary by region. Availability depends on your local integrated care board (ICB).
Why am I so tired on Mounjaro?
Exhaustion is a common side effect, especially when starting or increasing doses. It often improves within 2–4 weeks as your body adjusts. Ensure you're eating enough calories and staying hydrated. If fatigue persists, contact your prescriber—they may recommend holding your current dose longer before increasing.
What is the difference between private and NHS Mounjaro prescriptions?
NHS prescriptions require a GP referral and specialist assessment, with potential waiting lists. Private prescriptions are faster—you complete an online consultation with a UK-licensed prescriber and collect from a GPhC-registered pharmacy. Both require clinical assessment; costs differ significantly.
Is Mounjaro the same as tirzepatide?
Yes, Mounjaro is the brand name for tirzepatide, a dual GIP and GLP-1 receptor agonist. Both terms refer to the same medication. It's licensed in the UK for weight management and available through NHS and private routes depending on your eligibility and preference.
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.