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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Semaglutide Oral Dosage for Weight Loss — What You Need to Know
Semaglutide is a GLP-1 receptor agonist available in the UK for weight management, but in practice, it is primarily delivered as a once-weekly injection (Wegovy) rather than an oral tablet. This guide explains semaglutide dosage options, how it compares to Mounjaro's dual GIP and GLP-1 mechanism, and what clinical evidence shows about expected weight loss. If you're considering semaglutide for weight loss, understanding dosage, side effects, and suitability is essential before speaking with your GP or a licensed prescriber. Use our GLP-1 weight loss calculator above to explore potential outcomes at different doses.
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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.
Semaglutide Dosage, Mechanism, and Clinical Evidence
Semaglutide (the active ingredient in Wegovy for weight management) works as a GLP-1 receptor agonist — it mimics glucagon-like peptide-1, a natural hormone that regulates appetite and blood sugar. In the UK, semaglutide for weight loss is administered as a once-weekly subcutaneous injection; oral semaglutide tablets are not currently licensed for weight management in the UK, though they exist in research contexts.
Standard Wegovy dosing:
- Starting dose: 0.25 mg weekly for 4 weeks
- Escalation: 0.5 mg, 1 mg, 1.7 mg over 12 weeks
- Maintenance: 2.4 mg weekly (maximum licensed dose)
- Each dose increase occurs every 4 weeks if tolerated
In the STEP-1 clinical trial, participants on 2.4 mg semaglutide lost an average of 14.9% of their body weight over 68 weeks when combined with a reduced-calorie diet and increased physical activity. Individual results vary significantly. By contrast, Mounjaro (tirzepatide) — a dual GIP and GLP-1 agonist — achieved average weight loss of 15–21% across SURMOUNT trials at doses up to 15 mg weekly, suggesting a potentially stronger effect, though direct individual comparisons depend on many factors including baseline weight, metabolism, and adherence.
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Semaglutide vs Mounjaro — Key Differences and Suitability
Both semaglutide (Wegovy) and tirzepatide (Mounjaro) are prescription-only weight management injections licensed in the UK, but they work differently. Semaglutide activates only the GLP-1 pathway, whilst Mounjaro activates both GIP and GLP-1 receptors. This dual mechanism may contribute to Mounjaro's slightly higher average weight loss in trials, though individual response varies. Both require a clinical assessment before prescription — your prescriber will consider your BMI, weight-related health conditions, medications, and medical history.
Neither medication is suitable during pregnancy or breastfeeding. Side effects are similar between the two (nausea, diarrhoea, constipation, vomiting), though Mounjaro may carry a slightly higher incidence of gastrointestinal symptoms in early trials. Eligibility is the same: adults with a BMI of 30 or above, or 27 or above with weight-related conditions such as type 2 diabetes, hypertension, or sleep apnoea. Use our BMI calculator above to check your starting point, then discuss prescription options with your GP or a licensed online prescriber who can assess your individual suitability.
- 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 there an oral semaglutide tablet for weight loss available in the UK?
Not currently. Oral semaglutide tablets exist in research and some international markets, but they are not licensed for weight management in the UK. Wegovy (semaglutide for weight loss) is delivered as a once-weekly subcutaneous injection. Ozempic and other semaglutide formulations for diabetes are available orally, but they are not indicated for weight loss. Always follow your prescriber's guidance on the licensed formulation.
How does semaglutide compare to Mounjaro for weight loss?
In clinical trials, Mounjaro (tirzepatide) achieved average weight loss of 15–21%, whilst semaglutide (Wegovy) achieved approximately 14.9%. The difference is that Mounjaro is a dual GIP and GLP-1 agonist, whilst semaglutide is a GLP-1 agonist only. Both are effective; which is better for you depends on individual factors including your health profile, tolerance, and prescriber recommendation. Neither is "superior" — they work differently and suit different people.
What is the maximum dose of semaglutide for weight loss in the UK?
The maximum licensed dose of semaglutide (Wegovy) in the UK is 2.4 mg once weekly. This is reached after a 16-week escalation period starting at 0.25 mg. Some patients respond well at lower maintenance doses and may not need to progress to the maximum. Your prescriber will adjust your dose based on your response and tolerability.
Can I take semaglutide if I have type 2 diabetes?
Yes, semaglutide can be prescribed for weight loss in adults with type 2 diabetes if they meet the BMI and health criteria. However, if you are also taking diabetes medications such as insulin or sulphonylureas, your prescriber may need to adjust those doses because semaglutide itself affects blood sugar. Always inform your prescriber of all your current medications.
How long does semaglutide take to work for weight loss?
Weight loss typically begins within 2–4 weeks of starting semaglutide, though the most significant losses occur between weeks 8 and 20. Most of the average weight loss seen in clinical trials accumulated over the first 6 months. Results continue to improve up to 12 months. Consistency with diet, physical activity, and adherence to weekly injections is essential for best outcomes.
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.