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
One Month Before and After Weight Loss — What's Realistic?
One month is a short timeframe for significant weight loss, but meaningful progress is absolutely possible with the right support. If you're considering prescription weight management medication in the UK, understanding realistic expectations — and what's actually achievable in 30 days — matters. This guide covers UK-licensed weight loss options, eligibility, and how to start a conversation with your GP about prescription support. Use our free GLP-1 weight loss calculator to estimate potential outcomes at different medication doses.
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: What the Evidence Shows
The UK has three prescription-only medications licensed specifically for weight management. Mounjaro (tirzepatide), a once-weekly injection, showed average weight loss of 15–21% of body weight over 72 weeks in clinical trials — though results in just one month are typically more modest. Wegovy (semaglutide), also once-weekly, demonstrated average weight loss of around 15% over 68 weeks. Saxenda (liraglutide) is a daily injection with similar evidence profiles.
In the first month specifically, most users experience initial weight loss of 2–4 kg (4–9 lbs), particularly as the medication begins working. However, early weight loss often includes water weight. The real, sustainable fat loss typically becomes more evident from week 4 onwards as dosing builds and lifestyle changes take effect.
- Results vary significantly between individuals based on diet, exercise, starting weight, and genetics
- Medications work best alongside a reduced-calorie diet and increased physical activity
- Your GP or prescriber will assess your individual eligibility and expected timeline
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: Getting Started in One Month
If you want to start prescription weight loss medication within the next month, understanding your access options is crucial. NHS access requires referral to a tier 3 specialist weight management service — waiting times vary significantly by region, from weeks to several months in many areas. Private access through a GPhC-registered online pharmacy is typically faster: you can complete a clinical assessment, receive a prescription, and start treatment within 1–2 weeks.
Eligibility for prescription weight loss treatment in the UK requires: BMI of 30 or above, or BMI of 27–29.9 with at least one weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Speak with your GP first — they can discuss whether medication is appropriate for you, your medical history, and your best access route. Try our BMI calculator above to check your starting point.
If you want to start prescription weight loss medication within the next month, understanding your access options is crucial. NHS access requires referral to a tier 3 specialist weight management service — waiting times vary significantly by region, from weeks to several months in many areas. Private access through a GPhC-registered online pharmacy is typically faster: you can complete a clinical assessment, receive a prescription, and start treatment within 1–2 weeks.
Eligibility for prescription weight loss treatment in the UK requires: BMI of 30 or above, or BMI of 27–29.9 with at least one weight-related health condition (type 2 diabetes, high blood pressure, sleep apnoea, or cardiovascular disease). Speak with your GP first — they can discuss whether medication is appropriate for you, your medical history, and your best access route. Use our BMI calculator above to check your current BMI and healthy weight range.
- 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.
How much weight can I realistically lose in one month with prescription medication?
Most users experience 2–4 kg (4–9 lbs) of weight loss in the first month, though this includes initial water weight. Sustainable fat loss accelerates from week 4 onwards as medication builds up and lifestyle changes embed. Individual results vary based on starting weight, diet, exercise, and metabolism. Your prescriber can give more personalised projections.
Is one month enough time to see before-and-after changes?
Yes, one month is enough to notice changes in how clothes fit, energy levels, and how you feel. Visible physical changes depend on starting weight — heavier individuals typically see more obvious changes. Progress tracker tools help you log changes beyond the scale, including measurements and how you feel.
Which weight loss medication works fastest in the UK?
All three UK-licensed medications (Mounjaro, Wegovy, and Saxenda) work similarly, though Mounjaro may show slightly faster initial results in some users due to its dual mechanism. Speed isn't just about the medication — diet, exercise, and how consistently you follow medical guidance matter enormously. Discuss with your prescriber which option suits your health profile.
Can I get prescribed weight loss medication quickly on the NHS?
NHS specialist weight management services have significant waiting lists in most areas — typically weeks to months before your first appointment. If you need faster access, private online prescribing through GPhC-registered pharmacies can provide assessment and prescription within 1–2 weeks, though costs apply.
What should I do before starting prescription weight loss medication?
First, speak with your GP about your weight loss goals and medical history. They'll assess your eligibility, discuss medication options, and advise on diet and exercise alongside treatment. Check your BMI using a free calculator. Be honest about what you want to achieve — realistic goals over one month, three months, and beyond, set with professional guidance, lead to better long-term success.
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.