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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Coming Off Sertraline and Weight Loss — What You Need to Know
Coming off sertraline (an SSRI antidepressant) can sometimes influence your weight and metabolism. If you're concerned about weight management after stopping this medication, you're not alone — and there are evidence-based options available. For UK adults struggling with excess weight, prescription weight management options are now accessible through both NHS and private routes. This guide explains what's available and how to explore whether you might be eligible for treatment.
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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.
UK-Licensed Prescription Weight Management Options
If you've experienced weight changes related to sertraline or are looking to manage your weight after coming off it, several prescription weight loss medications are now licensed in the UK. These include Mounjaro (tirzepatide), a dual GIP and GLP-1 receptor agonist, and Wegovy (semaglutide), a GLP-1 agonist — both injected once weekly.
Clinical trials have shown these medications can help with weight management alongside reduced-calorie diet and increased physical activity. Individual results vary, but on average, adults have achieved 15–clinically studied weight loss with Mounjaro and approximately 15% with Wegovy.
- Mounjaro: starting dose 2.5 mg, maximum 15 mg weekly
- Wegovy: starting dose 0.25 mg, maximum 2.4 mg weekly
- Saxenda (liraglutide): daily injection, up to 3 mg — another licensed option
All three are prescription-only and require a clinical assessment before being prescribed. Use our free GLP-1 weight loss calculator to explore how these medications might support your weight management goals.
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 — Finding Out If You're Eligible
In the UK, you can access prescription weight loss medication through either the NHS or private prescribing, depending on your eligibility and circumstances.
NHS route: Your GP can refer you to your local specialist tier 3 weight management service. Eligibility generally requires a BMI of 30 kg/m² or above, or 27–29.9 with a weight-related health condition (such as type 2 diabetes, high blood pressure, or sleep apnoea). Availability varies significantly by region, and waiting lists can be long.
Private route: You can have an online consultation with a UK-licensed prescriber without an NHS referral. If clinically appropriate, you'll receive a prescription dispensed by a regulated pharmacy.
Start by calculating your BMI using our free BMI calculator to see where you fall, then speak with your GP about your weight management goals. They can advise on NHS options or support your decision to explore private treatment.
- 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 coming off sertraline cause weight changes?
Yes — some people experience weight loss when stopping SSRIs like sertraline, whilst others may find it harder to lose weight or gain weight. This varies greatly between individuals and depends on how sertraline was affecting your metabolism. Your GP can discuss your specific situation and explore weight management options if needed.
Am I eligible for prescription weight loss medication in the UK?
You may be eligible if you have a BMI of 30 kg/m² or above, or 27–29.9 kg/m² with a weight-related health condition like type 2 diabetes or high blood pressure. A GP or licensed prescriber can assess whether prescription weight loss treatment is suitable for you based on your individual health.
What's the difference between Mounjaro and Wegovy?
Mounjaro (tirzepatide) is a dual GIP and GLP-1 agonist, whilst Wegovy (semaglutide) is a GLP-1 agonist only. Both are once-weekly injections. Clinical trials showed Mounjaro resulted in an average of 15–clinically studied weight loss and Wegovy approximately 15%, though individual results vary significantly.
How long does it take to see weight loss results from these medications?
Most people begin noticing changes after 4–8 weeks, with more significant results typically visible at 12 weeks and beyond. These medications work best alongside reduced-calorie diet and increased physical activity. Your prescriber will monitor your progress and adjust your dose if needed.
Can I get prescription weight loss medication through the NHS?
Yes — your GP can refer you to a specialist tier 3 weight management service, where prescription medications may be offered. NHS eligibility and availability vary by region, so there may be waiting lists. Private prescribing via online consultation is also available as an alternative route.
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.