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
Low Carb Weight Loss with UK Prescription Medication
Low carb diets can be an effective way to manage weight, but combining dietary changes with prescription weight loss medication may offer additional support for eligible adults in the UK. If you're considering a low carb approach alongside medical treatment, it's worth understanding what prescription options are available, who qualifies, and how to access them through either the NHS or private prescribing. This guide explains the medication landscape for weight management in the UK and how to determine if treatment might be right for you.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
UK-Licensed Weight Loss Medications for Low Carb Dieting
Three prescription medications are licensed in the UK for weight management and can complement a low carb weight loss approach:
- Mounjaro (tirzepatide) — a once-weekly injection that activates dual GIP and GLP-1 pathways. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, alongside a reduced-calorie diet and physical activity.
- Wegovy (semaglutide) — a once-weekly GLP-1 receptor agonist. STEP trial data showed average weight loss of approximately 15% at the maximum dose of 2.4 mg.
- Saxenda (liraglutide) — a once-daily GLP-1 injection, with lower average weight loss outcomes than Mounjaro and Wegovy, but still effective for eligible adults.
All three are prescription-only and require a clinical assessment before dispensing. Individual results vary significantly based on adherence, diet quality, physical activity, and personal metabolism. Check your BMI using our free BMI calculator to see if you might meet initial eligibility criteria for these treatments.
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.
NHS vs Private Access and How to Get Started
In the UK, you can access weight loss medication through two routes:
- NHS: Referral to a tier 3 specialist weight management service from your GP. Availability varies significantly by region, and waiting times can be several months to over a year. NHS prescribing typically requires a BMI of 30 or above, or 27–29.9 with weight-related health conditions.
- Private: Online consultation with a UK-licensed prescriber followed by dispensing through a GPhC-registered pharmacy. No NHS referral needed. Available immediately if approved. Cost typically ranges from £129–£320+ per month depending on dose.
Start by speaking with your GP about weight loss options. They can assess your health, discuss whether medication is appropriate alongside your low carb diet, and either refer you to NHS services or advise on private routes. Track your progress with our free progress tracker to monitor results over time.
- 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 I use prescription weight loss medication with a low carb diet?
Yes. Weight loss medications like Mounjaro and Wegovy work alongside dietary changes and increased physical activity. A low carb approach may complement these medications, as both aim to reduce appetite and support sustainable weight loss. Always discuss your diet plan with your prescriber to ensure compatibility with your medication.
What BMI do I need to qualify for weight loss medication in the UK?
Generally, adults with a BMI of 30 or above are eligible. If your BMI is 27–29.9, you may qualify if you have weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Use our BMI calculator to check your current BMI, then discuss eligibility with your GP or a licensed prescriber.
How quickly will I lose weight on low carb diet plus medication?
The NHS recommends losing 0.5–1 kg per week for sustainable results. Clinical trials show average weight loss of 15–21% over several months with Mounjaro, though individual outcomes vary. Low carb diet combined with medication may produce faster initial results, but long-term success depends on maintaining both dietary changes and the medication regimen.
Is weight loss medication available through the NHS in my area?
Availability varies significantly across UK regions. Some ICBs (Integrated Care Boards) have well-established tier 3 weight management services with medication access; others have limited services or long waiting lists. Contact your GP to ask about services in your area, or explore private prescribing options if NHS access is delayed.
What side effects might I experience with weight loss injections on a low carb diet?
Common side effects include nausea, diarrhoea, and constipation — especially during the first few weeks. A low carb diet may amplify or ease some digestive effects depending on your individual response. Your prescriber will monitor you and adjust your dose if needed. Most side effects reduce over time as your body adjusts.
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.