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
Loss of Appetite When Losing Weight — Complete UK Options
Loss of appetite can actually be a sign that your weight loss efforts are working, but it's important to understand what's happening and which options suit your situation best. Whether you're looking to lose weight safely through lifestyle changes, access free NHS weight management support, or explore prescription medications, this guide covers all the options available in the UK and how to choose the right approach for you.
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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.
Weight Loss Options Available in the UK
The NHS weight management pathway offers several tiers of support depending on your needs and circumstances. Tier 1 includes self-help resources and free community programmes you can access directly. Tier 2 involves primary care-based interventions where your GP can provide behavioural support and access to digital tools like the NHS Weight Loss Plan. Tier 3 is specialist multidisciplinary weight management services, where prescription weight loss medication may be considered if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Tier 4 covers bariatric surgery for severe obesity. Lifestyle approaches—including calorie deficit diets, increased physical activity, and behavioural changes—remain the foundation of sustainable weight loss UK guidance recommends. For many people, losing weight safely means aiming for 0.5 to 1 kg per week. Prescription weight loss injections like Mounjaro and Wegovy are available through NHS specialist services or private prescribing if you meet eligibility criteria. Each option has different requirements and outcomes, so understanding your baseline health is essential.
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.
How to Choose the Right Approach for You
The best weight loss method depends on several factors: your current BMI, any weight-related health conditions, how much support you need, and your personal preferences. Start by calculating your BMI using our free BMI calculator to understand where you sit on the NHS scale—this often determines what options are available to you. If you have a BMI under 25, lifestyle changes alone are usually recommended. For BMI 25–29.9 without health conditions, structured diet and exercise remain the first line. If your BMI is 30 or above, or you have conditions like type 2 diabetes or high blood pressure, your GP may discuss prescription options or referral to tier 3 services. Try our GLP-1 weight loss calculator if you're curious about projected outcomes with injectable medications. Remember that sustainable weight loss combines dietary changes, increased physical activity, and often behavioural support—medication works alongside these, not instead of them.
- 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.
What causes loss of appetite during weight loss?
Loss of appetite can occur due to calorie restriction, changes in hormones that regulate hunger, or certain medications. It's often a sign your body is adapting to dietary changes. However, severe or prolonged appetite loss should be discussed with your GP to rule out underlying issues.
Is it safe to lose weight fast?
The NHS recommends sustainable weight loss of 0.5 to 1 kg per week. Faster loss risks muscle loss and nutrient deficiencies. Very gradual weight management (more than 1.5 kg weekly) should only be attempted under medical supervision.
Can I get free weight loss support on the NHS?
Yes. Tier 1 and Tier 2 support is free through your GP or local weight management services. These include digital tools, behaviour change programmes, and structured interventions. Waiting times vary by region.
Are prescription weight loss injections available on the NHS?
Mounjaro and Wegovy are NHS-available through specialist tier 3 weight management services for people with a BMI of 30 or above, or 27–29.9 with weight-related health conditions. Availability and waiting times vary significantly by region.
How do I know which weight loss option suits me?
Start with your GP, who can assess your health, calculate your BMI, and discuss your goals. Use our free BMI calculator to understand your starting point. Your GP can advise whether lifestyle changes, tier 2 programmes, specialist services, or medication are appropriate for your situation.
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.