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 Keto: What You Need To Know
Combining Mounjaro (tirzepatide) with a ketogenic diet is a question many UK adults considering weight loss ask. Mounjaro is a prescription-only GLP-1 and GIP receptor agonist that helps regulate appetite, whilst keto is a high-fat, low-carbohydrate eating approach. Both can support weight loss, but combining them requires careful consideration of nutrients, side effects, and individual health needs. This guide explains how they interact, who's eligible for Mounjaro in the UK, and how to access it through NHS or private prescription routes.
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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.
How Mounjaro And Keto Work Together
Mounjaro works by activating dual GIP and GLP-1 hormone pathways, which help regulate appetite and support feeling fuller after meals. A ketogenic diet creates a calorie deficit by restricting carbohydrates and increasing fat intake. In theory, combining them may amplify weight loss results — the medication suppresses appetite whilst the diet maintains metabolic adaptation.
Important considerations:
- Keto can cause nausea and digestive changes — Mounjaro side effects include similar symptoms (nausea, diarrhoea, constipation). This combination may intensify gastrointestinal effects.
- gradual weight management from combining both approaches increases risk of nutritional deficiencies, gallstones, and muscle loss.
- The SURMOUNT clinical trials for Mounjaro used a reduced-calorie diet, not keto specifically — individual results with keto are not clinically established.
- Keto can affect blood sugar control, which may interact with Mounjaro's insulin-regulating effects if you have prediabetes or type 2 diabetes.
Your prescriber or GP should be informed if you plan to use keto alongside Mounjaro so they can monitor your progress safely.
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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.
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Accessing Mounjaro In The UK: Cost And Routes
NHS access: Mounjaro (tirzepatide) is available through NHS tier 3 specialist weight management services, but you must be referred by your GP. Availability varies significantly by region and waiting lists can be lengthy — sometimes 6–12 months or longer depending on your local integrated care board (ICB). NHS prescriptions are free once initiated through specialist services.
Private access: Available through private online consultations with UK-licensed prescribers. Costs typically range from £130–£320 per month depending on the dose. To access privately, you'll have a brief online consultation assessing your BMI, medical history, and eligibility. If approved, a prescription is issued and dispensed by a GPhC-registered pharmacy. You can start treatment within days rather than waiting months.
Our GLP-1 weight loss calculator can help you estimate potential results with Mounjaro at different doses, informing your decision about which access route suits 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.
Can I use Mounjaro with a keto diet safely?
Mounjaro and keto can be combined, but both cause similar side effects (nausea, digestive changes) which may intensify together. gradual weight management from combining both raises nutritional deficiency and gallstone risks. Always inform your GP or prescriber if you plan keto alongside Mounjaro so they can monitor you. Individual clinical safety data for this specific combination is limited.
How much does Mounjaro cost in the UK privately?
Private Mounjaro costs typically range from £130–£320 per month depending on dose — lower doses cost less, whilst the maximum 15mg dose is most expensive. Costs vary between private providers. NHS prescriptions are free if accessed through specialist services, but waiting times can be 6–12 months or longer depending on your local ICB.
How do I get Mounjaro on the NHS in the UK?
You need a referral from your GP to a tier 3 specialist weight management service. Eligibility requires a BMI of 30+ or 27–29.9 with weight-related health conditions. However, NHS availability varies by region — some areas have long waiting lists. Contact your local integrated care board to check availability in your area.
What's the difference between Mounjaro and Wegovy for keto?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, whilst Wegovy (semaglutide) is a single GLP-1 agonist. Mounjaro showed ~20% average weight loss in trials versus ~15% for Wegovy, though individual results vary. Both have similar side effect profiles and interact with keto diet similarly. Choice between them depends on prescriber guidance and individual response.
Will Mounjaro work faster if I also do keto?
There's no clinical evidence that keto specifically accelerates Mounjaro's effects beyond standard calorie restriction. SURMOUNT trials used reduced-calorie diets, not keto. Faster weight loss from combining both approaches increases muscle loss and nutritional risks. Safe weight loss remains around 0.5–1kg weekly. Your GP can advise on the safest dietary approach for you personally.
Ready to take control of your weight loss journey?
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