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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Weight Loss With Sertraline — What You Need to Know
Sertraline is a common SSRI antidepressant prescribed in the UK that can sometimes affect weight management. If you're taking sertraline and concerned about weight loss, it's important to understand how this medication works, what side effects may impact your weight, and what prescription weight management options are available to you. This guide explains the relationship between sertraline and weight, and how to have an informed conversation with your GP about your health goals.
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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.
How Sertraline Affects Weight and Your Options
Sertraline and weight gain: Some people experience modest weight gain or difficulty losing weight when taking sertraline, though not everyone does. This can happen because SSRIs may increase appetite, reduce physical activity motivation, or affect metabolism slightly. Weight changes are typically modest (1–2 kg average) but vary between individuals.
If you're struggling with weight management while on sertraline, you have several options:
- Talk to your GP first. They may adjust your dose, switch to an alternative SSRI with lower weight impact, or discuss whether continuing sertraline is necessary for your mental health.
- Consider prescription weight loss medication. If you have a BMI of 30 or above (or 27 or above with weight-related health conditions), you may be eligible for licensed weight management medications such as Mounjaro, Wegovy, or Saxenda—even while taking sertraline. These work through different mechanisms and can complement your current treatment.
- Lifestyle support. A reduced-calorie diet and increased physical activity remain effective, and your GP can refer you to NHS weight management services for support.
Never stop sertraline without medical guidance—your GP can help you weigh the benefits and any side effects together.
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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.
Prescription Weight Loss Options Available in the UK
If you're eligible, the UK offers several prescription-only weight management medications that work independently of sertraline. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist available as a once-weekly injection. Wegovy (semaglutide) is a GLP-1 receptor agonist, also once weekly. Both are available through NHS specialist weight management services (with potential waiting lists) or private online prescribing following clinical assessment.
Clinical trials showed average weight loss of 15–21% body weight with these medications alongside diet and activity changes. Access through the NHS requires referral to a tier 3 specialist service; availability varies by region. Private access is available without NHS referral through GPhC-registered pharmacies. Your GP can assess whether you're eligible and discuss which option suits you best. Use our free BMI calculator above to check your current BMI and see if you might qualify.
- 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 I take sertraline and weight loss medication together?
Potentially yes, but requires careful prescriber assessment. Sertraline and GLP-1 medications (like Mounjaro or Wegovy) work through different mechanisms and are not contraindicated. However, your GP or prescriber must be aware of all medications you're taking. Some interactions are possible—for example, sertraline can affect how quickly food moves through your stomach, and GLP-1 medications do this too. Always inform your prescriber of all current medications before starting weight loss treatment.
Does sertraline cause weight gain in everyone?
No. Weight changes with sertraline vary between individuals. Some people experience no weight change, some gain slightly (average 1–2 kg), and some lose weight. Factors include the dose, how long you've taken it, your metabolism, diet, and activity level. If you're concerned about weight changes, discuss this with your GP—there may be alternatives with lower weight impact, or other strategies to support your health goals.
Should I stop taking sertraline to lose weight?
No—never stop sertraline without medical guidance. Stopping SSRIs abruptly can cause withdrawal symptoms and your mental health may be affected. If weight is a concern, speak to your GP. They can help you decide whether sertraline is still the right medication for you, explore dose adjustments, or discuss other options that might better suit your needs.
How do I find out if I'm eligible for prescription weight loss medication in the UK?
You're potentially eligible if you have a BMI of 30 or above, or 27 or above with weight-related health conditions (like type 2 diabetes, high blood pressure, or sleep apnoea). Use our free BMI calculator above to check your personal BMI. Then speak to your GP, who can assess your eligibility and discuss NHS specialist services or private prescribing options.
What's the difference between NHS and private weight loss medication access?
NHS access: Requires referral to a specialist tier 3 weight management service; availability varies by region and waiting lists can be long. Private access: Available through online prescribing following a clinical assessment; no NHS referral needed; faster access but involves a cost. Both require a prescription and medical assessment. Your GP can discuss which option is appropriate for you.
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.