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
Does Metformin Help With Weight Loss?
Metformin is a type 2 diabetes medication that may contribute to modest weight loss in some people, though it's not primarily a weight loss drug. Unlike prescription weight loss injections such as GLP-1 medications, metformin works by improving how your body uses insulin and may reduce appetite slightly. If you're exploring weight management options in the UK, it's important to understand how metformin compares to other treatments and whether it's appropriate for your individual circumstances.
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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 Metformin Affects Weight
Metformin may lead to modest weight loss in some patients, typically around 2–3 kg over several months, though results vary considerably. Unlike prescription weight loss injections designed specifically for weight management, metformin's primary purpose is to improve blood sugar control in type 2 diabetes. The modest weight loss occurs because metformin:
- Improves how your body responds to insulin, potentially reducing fat storage
- May slightly reduce appetite by affecting hunger hormones
- Can improve digestion and reduce bloating in some people
- Does not directly target weight loss like GLP-1 medications such as Wegovy do
For weight loss, metformin is considered a secondary benefit rather than the primary treatment goal. The NHS recognises metformin as a diabetes medication first, and any weight loss is an incidental advantage. If you have type 2 diabetes or prediabetes, your GP may prescribe metformin to manage blood sugar — weight loss may follow, but is not assured.
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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.
Metformin vs Prescription Weight Loss Medication
If weight loss is your primary goal, prescription weight loss injections are more effective than metformin alone. Medications like Wegovy (semaglutide), a GLP-1 receptor agonist, are licensed specifically for weight management and achieve average weight loss of approximately 15% of body weight in clinical trials — substantially more than metformin. However, these require a clinical assessment and prescription.
Metformin is suitable if you have type 2 diabetes or prediabetes, as it addresses both blood sugar control and may contribute to modest weight reduction. Use our free BMI calculator to assess your current weight category, and discuss with your GP which approach is right for your health needs. Your GP can help determine whether metformin, prescription weight loss medication, or lifestyle changes are most appropriate for your individual circumstances.
- 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 metformin alone help me lose weight?
Metformin may contribute to modest weight loss (2–3 kg) in some people, particularly if you have type 2 diabetes or are overweight with insulin resistance. However, it's not primarily a weight loss medication. Weight loss typically requires combining metformin with dietary changes and physical activity. Results vary considerably between individuals.
Is metformin more effective than Wegovy for weight loss?
No. Wegovy (semaglutide) is significantly more effective for weight loss, achieving average losses of around 15% of body weight in clinical trials, compared to metformin's modest 2–3 kg. However, Wegovy is prescription-only and designed specifically for weight management, whilst metformin is primarily a diabetes medication. Your GP can advise which is suitable for you.
What are the side effects of metformin?
Common side effects include nausea, diarrhoea, stomach upset, and metallic taste in the mouth — particularly when starting. Most side effects improve within a few weeks. Serious side effects are rare but can include lactic acidosis (very uncommon). Always inform your GP of any persistent side effects.
Will my GP prescribe metformin for weight loss alone?
Not typically. Metformin is primarily prescribed for type 2 diabetes or prediabetes. If weight loss is your only concern, your GP may discuss NHS weight management services, lifestyle interventions, or — if eligible — prescription weight loss medications. GPs assess eligibility based on BMI and health conditions.
Can I take metformin with other weight loss medications?
Possibly, but this requires careful medical assessment. If you have type 2 diabetes and are eligible for prescription weight loss medication, your GP or specialist will review all medications to check for interactions. Never combine medications without explicit prescriber guidance.
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.