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
Can Mounjaro Cause Hypoglycemia?
Hypoglycaemia (low blood sugar) is not a common direct side effect of Mounjaro in people without diabetes. However, if you take Mounjaro alongside diabetes medications like insulin or sulphonylureas, your risk of low blood sugar increases significantly. This is because Mounjaro enhances insulin release in response to food, which combined with existing diabetes medication can lower blood glucose too much. Your GP or prescriber should adjust your diabetes medications when starting tirzepatide to minimise this risk.
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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.
Hypoglycaemia Risk With Mounjaro and Diabetes Medication
Mounjaro (tirzepatide) works by activating GIP and GLP-1 receptors, which stimulate insulin release when you eat. In people without diabetes or prediabetes, this is safe — your body's natural feedback systems prevent blood sugar dropping too low. However, if you're already taking insulin injections or sulphonylurea tablets (such as gliclazide or glipizide), adding Mounjaro creates a higher insulin response, increasing hypoglycaemia risk.
- Insulin users: Your prescriber may reduce your insulin dose before starting Mounjaro
- Sulphonylurea users: Dose reduction or switching to safer alternatives may be recommended
- Type 2 diabetes on other medications: Metformin, GLP-1 drugs, and SGLT2 inhibitors carry lower hypoglycaemia risk alongside Mounjaro
This is why a full medication review is essential before starting a Mounjaro KwikPen. Always inform your prescriber of all diabetes medications you take.
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.
Signs of Low Blood Sugar and When to Seek Help
Hypoglycaemia symptoms include trembling, sweating, palpitations, dizziness, difficulty concentrating, and feeling anxious or irritable. If you experience these symptoms, test your blood sugar if possible and consume a fast-acting carbohydrate (fruit juice, glucose tablets, or a sugary drink). Seek urgent medical attention if symptoms don't improve within 15 minutes or if you lose consciousness.
Prevention is key: Carry fast-acting carbohydrates at all times if you're at risk. Monitor your blood glucose more frequently when starting Mounjaro, especially if you're on insulin or sulphonylureas. Use our free BMI calculator and GLP-1 weight loss calculator to track your health metrics alongside your prescriber's monitoring.
- 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 cause hypoglycaemia in people without diabetes?
Mounjaro rarely causes hypoglycaemia in non-diabetic people because your body's natural glucose regulation prevents blood sugar dropping dangerously low. However, if you have prediabetes, your risk is slightly higher. Your prescriber will assess your individual risk during the clinical assessment before prescribing tirzepatide.
What diabetes medications increase hypoglycaemia risk with Mounjaro?
Insulin injections and sulphonylureas (like gliclazide) carry the highest risk because they already lower blood sugar. When combined with Mounjaro's insulin-stimulating effect, hypoglycaemia becomes more likely. Your GP should review and potentially adjust these medications before starting tirzepatide.
How is hypoglycaemia risk managed when starting Mounjaro?
Your prescriber will conduct a full medication review and may reduce doses of insulin or sulphonylureas. You'll receive clear safety guidance on recognising low blood sugar symptoms, carrying emergency carbohydrates, and testing your blood glucose more frequently during the initial weeks of Mounjaro dose titration.
Can I take Mounjaro if I'm on insulin for type 2 diabetes?
Yes, but with careful management. Many people take Mounjaro and insulin together successfully. However, your insulin dose will likely need reduction, and you'll require close monitoring from your GP or diabetes team. Never adjust insulin doses yourself — always follow your prescriber's guidance.
What should I do if I have a hypoglycaemic episode while on Mounjaro?
Consume fast-acting carbohydrates immediately (juice, glucose tablets, sugary drink). Rest and retest your blood sugar after 15 minutes. If symptoms persist or worsen, call 999 or go to A&E. Always carry emergency carbohydrates and wear medical identification stating you're on weight loss medication combined with diabetes treatment.
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.