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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Can Mounjaro Cause Hypoglycemia?
Hypoglycaemia (low blood sugar) is not a common side effect of Mounjaro on its own, but the risk increases significantly if you're also taking other diabetes medications like insulin or sulphonylureas. This guide explains when Mounjaro may increase hypoglycaemia risk, what symptoms to watch for, and when to seek medical advice. If you're considering Mounjaro or already taking it alongside other medications, understanding this risk is essential for safe use. Always discuss your full medication history with your prescriber before starting Mounjaro or adjusting any doses.
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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.
When Does Mounjaro Increase Hypoglycaemia Risk?
Mounjaro (tirzepatide) itself does not typically cause low blood sugar in people without diabetes. However, if you're taking insulin or sulphonylurea medications (such as gliclazide or glipizide) for type 2 diabetes alongside Mounjaro, your risk of hypoglycaemia increases because Mounjaro enhances insulin sensitivity and may reduce the amount of glucose your body needs to regulate.
- Insulin users: Your prescriber may need to reduce your insulin dose when starting Mounjaro
- Sulphonylurea users: Similar dose adjustments may be necessary to prevent low blood sugar episodes
- Metformin only: If you take only metformin (which does not cause hypoglycaemia alone), your risk remains very low
- People without diabetes: Hypoglycaemia is exceptionally rare if you have no underlying diabetes
This is why your prescriber will ask about all diabetes medications during your clinical assessment. If you're on insulin or a sulphonylurea, your doses may need adjusting when starting or increasing Mounjaro doses.
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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.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Hypoglycaemia Symptoms and When to Seek Help
Know the warning signs of low blood sugar, especially if you're taking Mounjaro alongside insulin or other diabetes medication. Early symptoms include trembling, sweating, rapid heartbeat, anxiety, dizziness, hunger, and difficulty concentrating. More severe symptoms include confusion, slurred speech, loss of consciousness, or seizures.
If you experience any hypoglycaemia symptoms, stop what you're doing and consume a fast-acting carbohydrate immediately—such as 15g of glucose (3–4 glucose tablets), 150ml of sugary drink, or 15g of honey. Recheck your blood sugar after 15 minutes. If symptoms persist, seek medical attention. Contact your GP or call 111 if you're unsure, especially if episodes happen repeatedly. Your prescriber may need to adjust your medications.
- 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.
Is hypoglycaemia a common side effect of Mounjaro?
No. Hypoglycaemia is not listed as a common side effect of Mounjaro when used alone. It becomes a concern only if you're also taking insulin or sulphonylurea medications for diabetes. Your prescriber assesses this risk during your clinical assessment and may adjust your diabetes medication doses if needed.
What should I do if I experience low blood sugar on Mounjaro?
Consume a fast-acting carbohydrate immediately—such as 15g of glucose tablets, a sugary drink, or honey. Wait 15 minutes and recheck your blood sugar. Inform your GP or prescriber if this happens, as your insulin or sulphonylurea dose may need adjusting. Seek emergency care if symptoms are severe or you lose consciousness.
Do I need to monitor my blood sugar if I take Mounjaro?
If you have type 2 diabetes and take insulin or sulphonylureas alongside Mounjaro, yes—you should monitor your blood sugar as directed by your prescriber. They may recommend more frequent checks when starting Mounjaro or adjusting doses. If you take only metformin or have no diabetes, routine blood sugar monitoring is unlikely to be necessary.
Can my diabetes medication doses stay the same when I start Mounjaro?
Not always. If you take insulin or a sulphonylurea, your prescriber may reduce your dose when starting Mounjaro to prevent hypoglycaemia. Never adjust your own medication doses—always discuss any changes with your GP or the prescriber who assessed you for Mounjaro.
What's the difference between Mounjaro and Wegovy regarding hypoglycaemia risk?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) can increase hypoglycaemia risk if you're taking insulin or sulphonylureas, though tirzepatide's dual GIP and GLP-1 action may affect insulin sensitivity slightly differently. Your prescriber will assess your individual risk based on your diabetes medications and adjust doses accordingly. ```
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