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
Best Time to Take Metformin for Weight Loss
Metformin is not primarily a weight loss medication — it's a prescription diabetes medication that may support modest weight loss as a secondary effect. If your GP has prescribed metformin, the best time to take it depends on your individual dose schedule and how your body responds. This guide explains metformin timing, how it works, and how it fits into broader weight management in the UK. Always follow your prescriber's instructions, as timing can affect side effects and effectiveness.
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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 Metformin Affects Weight
Metformin is a first-line medication for type 2 diabetes that works by reducing glucose production in the liver and improving insulin sensitivity. Unlike prescription weight loss injections such as GLP-1 receptor agonists (like Wegovy or Mounjaro), metformin is not designed to suppress appetite or slow digestion. Weight loss associated with metformin is typically modest — averaging 2–3 kg over several months — and occurs mainly through improved blood sugar control and modest reduction in appetite.
- Metformin may reduce cravings by stabilising blood sugar levels
- It does not directly signal to the brain to feel fuller, unlike GLP-1 medications
- Weight loss is often a secondary benefit, not the primary purpose
- Results vary significantly between individuals
If significant weight loss is your goal, your GP may discuss whether additional prescription weight loss medication might be appropriate alongside lifestyle changes. Use our free BMI calculator above to track where you stand relative to NHS healthy weight guidelines.
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.
Best Timing for Metformin Dosage
Metformin is typically prescribed in two or three daily doses with meals to minimise stomach upset — the most common side effect. Taking metformin with food reduces nausea and indigestion, which can otherwise discourage people from continuing treatment. Your GP or prescriber will specify the exact timing for your dose schedule (usually morning, lunchtime, and evening with food).
- Take metformin with or shortly after meals — not on an empty stomach
- Consistent timing each day helps your body adapt and reduces side effects
- If you miss a dose, take it as soon as you remember — unless it's nearly time for your next dose
- Never double-dose to make up for a missed dose
Timing consistency matters more than the specific time of day. Work with your prescriber if side effects persist — dose adjustments or extended-release formulations may help. For comprehensive weight management support, track your progress using our free progress tracker.
- 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 metformin used for weight loss in the UK?
Metformin is not a weight loss medication — it's prescribed for type 2 diabetes. Weight loss is a potential secondary effect in some people, typically 2–3 kg over months. If weight loss is your primary goal, prescription weight loss injections or NHS weight management services may be more appropriate. Discuss options with your GP.
What time of day should I take metformin?
Take metformin at the time your GP or prescriber specifies, always with food or shortly after meals. This minimises stomach upset. Consistency matters more than the specific time — if you take it with breakfast and dinner, stick to that routine daily. Follow your prescription instructions exactly.
Can I take metformin on an empty stomach?
No — taking metformin without food significantly increases the risk of nausea, indigestion, and stomach discomfort. Always take it with or immediately after a meal. If side effects persist despite taking it with food, contact your prescriber — dose adjustments or extended-release formulations may help.
How much weight can metformin help me lose?
Average weight loss with metformin alone is modest — typically 2–3 kg over several months. Weight loss is not assured and varies between individuals. For more significant weight loss, NHS weight loss programmes, lifestyle changes, or prescription weight loss medications (following clinical assessment) may be more effective.
Is metformin the same as Wegovy or Mounjaro?
No — metformin is a diabetes medication that may support modest weight loss as a side effect. Wegovy and Mounjaro are prescription-only weight loss injections that work by suppressing appetite and are licensed specifically for weight management. They are different medication classes with different mechanisms. Your GP can advise which is appropriate for you.
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.