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
Testosterone and Weight Loss — What You Need to Know
Testosterone plays an important role in metabolism and body composition, and low testosterone levels can make weight management more challenging. However, if you're struggling with weight loss in the UK, there are evidence-based prescription options available regardless of testosterone status. This guide explains the connection and outlines the medication options available to eligible adults through both NHS and private routes.
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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.
Prescription Weight Loss Medication Available in the UK
If you have a BMI of 30 or above, or a BMI of 27–29.9 with weight-related health conditions, you may be eligible for prescription weight loss medication in the UK. The most widely available options are:
- Mounjaro (tirzepatide) — a dual GIP and GLP-1 receptor agonist injection given once weekly. Clinical trials showed participants lost an average of 15–21% of their body weight over 72 weeks, alongside lifestyle changes.
- Wegovy (semaglutide) — a GLP-1 receptor agonist injection, also once weekly. Average weight loss in trials was approximately 15% of body weight.
- Saxenda (liraglutide) — a daily GLP-1 injection option, though less commonly used than the weekly options.
These medications work by regulating appetite signals and supporting fullness, making them useful tools within a comprehensive weight management approach. Use our free GLP-1 weight loss calculator to see projected results at different doses, and check your BMI using our free BMI calculator to understand your eligibility.
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.
Getting Started — NHS vs Private Routes
In the UK, NHS access to prescription weight loss medication is typically through specialist tier 3 or 4 weight management services. Your GP can refer you, though waiting lists vary significantly by region and may extend several months. Private access is available through licensed online prescribers who conduct a clinical assessment before issuing a prescription — this route often has shorter wait times.
Regardless of your testosterone levels, a prescriber will assess whether medication is suitable based on your individual health profile, other medications, and medical history. If weight is a concern for you, speak to your GP or explore private prescribing options. You can also use our free progress tracker to log your weight loss journey and monitor your health improvements 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.
Does low testosterone affect weight loss?
Yes, low testosterone can make weight loss more difficult because testosterone supports muscle mass and metabolic rate. Men with low testosterone may experience slower metabolism and easier fat gain. However, prescription weight loss medications like GLP-1 injections can still be effective tools for weight management, and your GP can assess whether testosterone levels need addressing separately.
Can I take weight loss injections if I have low testosterone?
Yes. Prescription weight loss medications like Mounjaro and Wegovy are assessed based on BMI and health conditions, not testosterone levels. A prescriber will review your full health history and any existing treatments before deciding if medication is appropriate for you. Always inform them of any ongoing medical conditions or treatments.
What's the difference between Mounjaro and Wegovy for weight loss?
Mounjaro (tirzepatide) activates two hormone pathways (GIP and GLP-1), while Wegovy (semaglutide) activates one (GLP-1 only). Clinical trials suggest Mounjaro may produce slightly larger average weight loss, but individual results vary. Both are once-weekly injections and require a prescription from a licensed UK prescriber.
How do I know if I'm eligible for NHS weight loss medication?
You may be eligible if you have a BMI of 30 or above, or 27–29.9 with weight-related health conditions like high blood pressure, type 2 diabetes, or sleep apnoea. Ask your GP about referral to your local NHS weight management service. You can check your BMI using our free BMI calculator on this page.
Are there side effects I should know about?
Common side effects of GLP-1 medications include nausea, diarrhoea, and stomach discomfort, though these often reduce over time. More serious but rare side effects include pancreatitis symptoms. A prescriber will discuss all potential side effects and contraindications with you before prescribing. Always report unusual symptoms to your healthcare provider.
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.