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
Can You Take Sertraline With Mounjaro?
Sertraline (an antidepressant) and Mounjaro (tirzepatide, a weight management injection) can often be used together, but there are important considerations to understand. If you're taking both medications or considering starting one whilst on the other, it's essential to inform your GP or prescriber. This guide explains the interaction, what to watch for, and how your prescriber will assess safety for your individual situation.
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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.
What You Need To Know About Both Medications
Sertraline is a selective serotonin reuptake inhibitor (SSRI) commonly prescribed in the UK for depression, anxiety, and OCD. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist approved by the MHRA for weight management in UK adults. There is no direct pharmacological interaction between sertraline and the tirzepatide molecule itself — they work through different mechanisms in the body. However, both medications can affect appetite and gastrointestinal function, which means combined use requires careful monitoring.
- Sertraline may increase or decrease appetite depending on the individual
- Mounjaro often reduces appetite and can cause nausea, diarrhoea, or constipation
- Combined effects on the gut may be more pronounced — your prescriber needs to know about both
- Neither medication is contraindicated with the other, but assessment is essential
Always tell any prescriber about all medications you're taking, including over-the-counter and herbal products.
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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.
What Your GP Or Prescriber Will Check
Before prescribing Mounjaro alongside sertraline, your GP or weight management prescriber will review your full medical history, current symptoms, and how well each medication is working. They'll assess whether the combined gastrointestinal effects could be problematic — for example, if you already experience nausea or appetite changes from sertraline, starting Mounjaro may require dose adjustments or closer monitoring.
- Your mental health stability on sertraline
- Any current digestive symptoms or gastroparesis history
- Whether sertraline has affected your weight or appetite
- Your BMI, weight loss goals, and eligibility for Mounjaro
- Frequency of appointments to monitor both conditions
Your prescriber may recommend a slower dose escalation schedule for Mounjaro or more frequent check-ins to ensure both medications remain safe and effective for you.
- 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 a direct drug interaction between sertraline and Mounjaro?
No direct pharmacological interaction has been identified between sertraline and tirzepatide. However, both can affect appetite and gastrointestinal function, so combined use requires assessment. Always inform your GP or prescriber that you take sertraline before starting Mounjaro.
Can sertraline stop Mounjaro from working?
Sertraline does not reduce the effectiveness of Mounjaro's weight loss mechanism. However, if sertraline affects your appetite, this may interact with Mounjaro's appetite-suppressing effects. Your prescriber will monitor your response to both medications.
What side effects might be worse when taking both medications?
Nausea, reduced appetite, and changes to bowel habits may be more noticeable when combining sertraline and Mounjaro. If you experience persistent nausea, vomiting, or severe gastrointestinal symptoms, contact your GP — your Mounjaro dose may need adjustment.
Do I need to stop sertraline to use Mounjaro?
No. Most people safely take both medications together. However, you must inform your prescriber about your sertraline use before starting Mounjaro. Your prescriber will assess whether it's safe for you individually and plan appropriate monitoring.
Where can I get Mounjaro if I'm already on sertraline?
Mounjaro is available through NHS specialist tier 3 weight management services (via GP referral) or through private online prescribing with a UK-licensed prescriber. Both routes require a clinical assessment where you'll disclose your sertraline use. Your GP can advise on NHS availability in your area.
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.