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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Does Carnitine Help with Weight Loss?
Carnitine is an amino acid compound that's often marketed as a weight loss supplement in the UK. While it plays a real role in fat metabolism, the evidence for its effectiveness as a standalone weight loss tool is limited. Most clinical studies show carnitine produces minimal weight loss compared to dietary changes and exercise alone. If you're exploring weight management options, understanding what carnitine can and cannot do is important before spending money on supplements. This guide covers the science, the claims, and what actually works for sustainable weight loss in the UK.
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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.
What Is Carnitine and How Does It Work?
L-carnitine is a naturally occurring amino acid derivative produced mainly in your liver and kidneys. It plays a genuine role in fat metabolism by transporting long-chain fatty acids into mitochondria (the energy-producing centres of your cells) so they can be burned for energy. This real biological function has led to the popular claim that carnitine supplements can boost fat burning and support weight loss.
However, most people eating a balanced diet already produce enough carnitine naturally. The body also obtains carnitine from meat, fish, and dairy products. Taking additional carnitine supplements does not automatically increase fat burning — the evidence suggests that only in specific circumstances (such as severe deficiency, which is rare) does supplementation have a measurable effect on weight.
- Natural sources: Red meat, chicken, dairy, nuts, seeds
- Body production: Synthesised in the liver and kidneys from amino acids
- Typical supplement dose: 1,000–4,000 mg daily (often L-carnitine or acetyl-L-carnitine)
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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
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What Does the Evidence Show About Carnitine and Weight Loss?
Clinical trials on carnitine supplementation have produced disappointing results for weight loss. A 2021 systematic review found that while carnitine supplements did produce some weight loss, the effect was minimal — averaging only 1–2 kg over several weeks to months, often no better than placebo in rigorous studies. Most weight loss occurred when carnitine was combined with calorie restriction and exercise, making it impossible to isolate carnitine's independent effect.
For sustainable weight management in the UK, the NHS emphasises proven approaches: a consistent calorie deficit of around 500 kcal daily (supporting approximately 0.5 kg weekly loss), increased physical activity, and behaviour change. Use our free BMI calculator to understand your current weight status, and our weight converter to track progress across different measurements. If you're interested in prescription weight management options, our GLP-1 weight loss calculator can show projected outcomes with evidence-based medications like Mounjaro and Wegovy.
- 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 carnitine safe to take as a supplement?
Carnitine supplements are generally well tolerated at normal doses (up to 3,000 mg daily). Side effects are usually mild — nausea, diarrhoea, or headache in some people. However, people with certain medical conditions, kidney disease, or taking specific medications should consult their GP before supplementing. High doses may interact with diabetes medications or blood thinners.
Why do carnitine supplements often claim to help weight loss if the evidence is weak?
Marketing for carnitine supplements emphasises its real biological role in fat transport, but this doesn't translate into significant weight loss in practice. Most studies showing weight loss combined carnitine with strict calorie restriction and exercise — meaning the weight loss likely came from diet and activity, not the supplement itself. Supplement companies can make limited claims about carnitine's role in metabolism without proving it causes weight loss.
What are proven alternatives to carnitine for weight loss in the UK?
Evidence-based approaches include: NHS weight management programmes (tier 1–3 services), prescription medications like Mounjaro and Wegovy (GLP-1/GIP-1 receptor agonists), structured diet plans with a calorie deficit, increased physical activity, and behaviour change support. These have strong clinical evidence. Prescription weight loss medications require assessment by a GP or licensed prescriber and a BMI of 30+ (or 27+ with health conditions).
Can carnitine replace diet and exercise for weight loss?
No. Carnitine cannot replace the calorie deficit and physical activity required for weight loss. Even in clinical trials where carnitine was combined with these lifestyle factors, carnitine's independent contribution was minimal. The NHS recommends a sustainable calorie deficit (around 500 kcal daily for ~0.5 kg weekly loss) alongside increased activity as the foundation of weight management — supplements are not a substitute.
Is carnitine better than GLP-1 weight loss medications like Wegovy or Mounjaro?
No. GLP-1 medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) are prescription-only, licensed weight loss medications with strong clinical evidence. Wegovy trials showed average weight loss of around 15% body weight; Mounjaro trials showed 15–21% loss. Carnitine supplements showed minimal independent weight loss in studies. Prescription medications are not suitable for everyone and require clinical assessment, but the evidence strongly favours them over carnitine for meaningful weight loss.
Ready to take control of your weight loss journey?
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