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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Mounjaro and Sertraline — What UK Patients Need to Know
If you're taking sertraline (a common antidepressant) and considering Mounjaro for weight management, it's important to understand how these medications interact. Mounjaro (tirzepatide) is a prescription-only GLP-1 and GIP receptor agonist licensed in the UK for adults with obesity or overweight with weight-related health conditions. Sertraline is an SSRI (selective serotonin reuptake inhibitor) used to treat depression and anxiety. Both are commonly prescribed in the UK, but combining them requires careful assessment by your GP or prescriber to ensure they're safe together for your individual health 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.
Can You Take Mounjaro with Sertraline?
Yes, Mounjaro and sertraline can typically be taken together, as there are no known direct contraindications between tirzepatide and sertraline reported in clinical data. However, this does not mean they are automatically safe for every individual — your prescriber must assess your complete medical history and current medications before issuing a prescription.
Key considerations when combining these medications:
- Mounjaro may slow gastric emptying (how quickly food leaves the stomach), which could theoretically affect how your body absorbs sertraline. This effect typically reduces over time as your body adjusts to the injection.
- Both medications can cause nausea, particularly when starting Mounjaro. Your prescriber may need to monitor you more closely initially to distinguish between side effects.
- Sertraline may be affected by reduced food intake if Mounjaro significantly suppresses your appetite — discuss this with your GP if you notice changes in how you feel on your current antidepressant dose.
- Some SSRIs including sertraline have been associated with weight gain in some patients, which is why weight management medication may be particularly relevant for you.
Always inform your prescriber about all medications, including over-the-counter products and supplements, before starting Mounjaro.
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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.
How to Get a Safe Prescription
If you take sertraline and want to access Mounjaro in the UK, follow these steps:
- NHS route: Request a referral from your GP to a specialist tier 3 weight management service. Tell your GP about your sertraline use — they will assess whether specialist weight management is appropriate and refer you if eligible. Waiting lists vary by region but can be lengthy.
- Private route: Use a GPhC-registered online prescribing service. During your online consultation, you'll be asked about all current medications including sertraline. A UK-licensed prescriber will review your full health profile and decide whether Mounjaro is safe for you. If approved, you'll receive a prescription and the medication is dispensed by a regulated pharmacy.
- Whichever route you choose, be completely honest about your mental health medication and any other treatments. Your prescriber needs full information to make a safe decision.
- 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 Mounjaro safe to take with sertraline?
There are no known direct contraindications between Mounjaro (tirzepatide) and sertraline, meaning they can potentially be used together. However, individual safety must be assessed by a UK-licensed prescriber who reviews your complete medical history, current doses, and any other medications. Always disclose all medications during your clinical assessment.
Will Mounjaro affect how my sertraline works?
Mounjaro may slow gastric emptying initially, which could theoretically affect sertraline absorption, though this effect usually diminishes over time. Both can cause nausea, so your prescriber may monitor you closely when starting. If you notice changes in your mood or anxiety levels, inform your GP — your sertraline dose may need adjustment.
Can sertraline and Mounjaro both cause nausea?
Yes, nausea is a common side effect of Mounjaro, and sertraline can also cause nausea, especially when starting. Your prescriber will want to know about this potential overlap. Most Mounjaro-related nausea improves as your body adjusts, particularly if you start at the lowest dose (2.5 mg) and follow dietary guidance.
What should I tell my prescriber about my sertraline?
Tell your prescriber the specific antidepressant (sertraline), your current dose, how long you've been taking it, and how well it works for you. Mention any side effects you experience. This helps them assess whether Mounjaro is appropriate and whether any dose adjustments to either medication might be needed.
Can I access Mounjaro on the NHS if I take sertraline?
Yes, sertraline use doesn't automatically exclude you from NHS weight management services. Ask your GP for a referral to tier 3 specialist services if you meet eligibility criteria (BMI ≥30, or BMI 27–29.9 with weight-related health conditions). The specialist team will assess your suitability for Mounjaro, including your current antidepressant therapy.
Ready to take control of your weight loss journey?
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