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 a potential side effect of Mounjaro, especially in people taking other diabetes medications. Mounjaro (tirzepatide) is a GIP and GLP-1 receptor agonist that helps regulate blood sugar levels, but this effect can sometimes cause blood sugar to drop too low. Understanding the risk, recognising symptoms, and knowing when to seek help is essential if you're prescribed this UK weight loss injection. Your GP or prescriber should discuss this risk during your clinical assessment before starting treatment.
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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.
How Mounjaro Affects Blood Sugar Levels
Mounjaro works by activating two hormone pathways — GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) — that help regulate blood sugar. In people without diabetes, this typically causes blood sugar to normalise. However, the risk of hypoglycaemia increases significantly if you're also taking insulin or sulphonylurea medications (such as gliclazide or glibenclamide) for type 2 diabetes.
When Mounjaro is combined with these diabetes drugs, blood sugar can drop to dangerously low levels because both the medication and Mounjaro are actively lowering glucose. Your prescriber may adjust your diabetes medication doses before or during Mounjaro treatment to prevent this. This is why medical supervision and regular blood sugar monitoring are essential, and why you must inform your prescriber of all medications before starting tirzepatide.
- Risk is highest in those taking insulin or sulphonylureas
- People with type 2 diabetes but no other diabetes medication have lower hypoglycaemia risk
- Those without diabetes rarely experience hypoglycaemia from Mounjaro alone
- Dose titration and medication adjustment help manage this risk
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.
Recognising and Managing Low Blood Sugar Symptoms
Hypoglycaemia symptoms develop quickly and include shakiness, dizziness, sweating, rapid heartbeat, anxiety, hunger, and difficulty concentrating. Mild hypoglycaemia can usually be a UK pharmacy by consuming 15–20 grams of fast-acting carbohydrate — such as a glass of juice, a handful of sweets, or a glucose tablet.
Severe hypoglycaemia (where you cannot treat yourself safely) is a medical emergency requiring immediate hospital attention. Always carry a source of fast-acting carbohydrate with you if you're at risk. Inform your family and friends about hypoglycaemia symptoms so they can help. Your GP can provide a blood sugar meter and advise on monitoring frequency. Regular review appointments are essential to detect any patterns in blood sugar drops and adjust treatment accordingly.
- 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?
Hypoglycaemia is not common in people taking Mounjaro alone without diabetes medication. It becomes more likely (though still relatively uncommon) in those also taking insulin or sulphonylureas. Your prescriber will assess your individual risk during clinical assessment and monitor you for symptoms throughout treatment.
What should I do if I think I have low blood sugar while on Mounjaro?
If you experience symptoms like shakiness, sweating, dizziness, or rapid heartbeat, consume 15–20g of fast-acting carbohydrate immediately (juice, sweets, glucose tablet). Rest and recheck your blood sugar if possible. Seek urgent medical attention if symptoms don't improve within 15 minutes or if you lose consciousness.
Will my diabetes medication doses change when I start Mounjaro?
Possibly. Your prescriber may reduce your insulin or sulphonylurea doses before starting Mounjaro to lower hypoglycaemia risk. This is why you must inform your prescriber of all medications. Never adjust medication doses yourself — always follow your prescriber's guidance. Regular blood sugar monitoring helps detect if adjustments are needed.
Can I use our GLP-1 weight loss calculator if I'm at risk of hypoglycaemia?
Our free weight loss calculator provides general weight loss projections but does not account for individual diabetes risk or medication interactions. Always discuss specific health concerns with your GP or the prescriber who assessed you for Mounjaro. They can give personalised advice about safety and expected outcomes.
How often should I monitor my blood sugar on Mounjaro?
If you're at risk of hypoglycaemia (taking insulin or sulphonylureas), your GP will recommend monitoring frequency — typically several times daily initially. People without diabetes but at lower risk may monitor less frequently. Your prescriber will provide clear guidance based on your individual circumstances during clinical review appointments.
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.