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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Does Mounjaro Cause Depression or Anxiety?
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK. Some people taking Mounjaro have reported mood changes, including depression and anxiety, though the connection remains unclear. This guide explains what the evidence shows, distinguishes between weight loss-related mood improvements and medication side effects, and advises when to speak to your GP. Mental health concerns deserve prompt attention, so understanding what's normal and what warrants medical review is important for anyone taking this medication.
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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.
What Does the Evidence Say About Mounjaro and Mental Health?
Clinical trials for Mounjaro (tirzepatide) did not identify depression or anxiety as common reported side effects. In the SURMOUNT trials, mood changes were not listed in the standard safety data. However, this does not mean the medication cannot affect mental health — clinical trials may not capture all individual experiences, and some people taking GLP-1 and GIP/GLP-1 medications have reported depressive symptoms or anxiety in real-world use.
Why the confusion? Weight loss itself often improves mood and mental health, so people typically feel better emotionally while taking these medications. Conversely, some individuals experience low mood, emotional blunting, or increased anxiety. The cause may be related to how tirzepatide affects brain chemistry, nutrient absorption, or gradual weight management. It could also reflect an individual's baseline mental health vulnerabilities being affected by metabolic changes.
The UK regulatory authority (MHRA) continues to monitor tirzepatide safety reports, including any mental health effects reported by patients or healthcare professionals.
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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.
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When Should You Contact Your GP About Mood Changes?
If you experience persistent low mood, loss of interest in activities you normally enjoy, anxiety that interferes with daily life, or thoughts of self-harm after starting Mounjaro, contact your GP immediately. These warrant prompt assessment regardless of whether depression is listed as a known side effect.
Important context: Not all mood changes are caused by Mounjaro. Weight loss can trigger emotional shifts — some positive (increased confidence, energy) and some challenging (grief over lifestyle changes, body image adjustment). Your GP can help distinguish between expected emotional changes and concerning mental health symptoms that may require intervention or medication adjustment.
Never stop taking Mounjaro without medical guidance, but always prioritise mental health concerns by discussing them with your healthcare provider as soon as possible.
- 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 depression listed as a side effect of Mounjaro in the UK?
Depression and anxiety are not listed as very common or common side effects in the SURMOUNT clinical trials or UK prescribing information for Mounjaro. However, individual experiences vary, and some people have reported mood changes in real-world use. If you experience depression symptoms, inform your GP regardless of whether it appears in the official list.
Could Mounjaro's effects on the brain cause depression?
Tirzepatide activates GIP and GLP-1 receptors, which influence appetite regulation and nutrient absorption. These pathways are also present in brain regions affecting mood and motivation. While the mechanism is not fully understood, it's plausible that changes in these systems could affect mental health in some individuals, though this varies considerably.
How do I know if my low mood is from Mounjaro or just weight loss adjustment?
Weight loss can trigger complex emotions — relief, confidence, but also grief and identity shifts. Your GP can assess the timing, severity, and context of your symptoms. If low mood began shortly after starting Mounjaro and persists despite positive weight loss, discuss this with your healthcare provider. They may adjust your dose, monitor more closely, or explore other factors.
What should I do if I feel depressed or anxious while taking Mounjaro?
Contact your GP promptly. Do not stop Mounjaro without guidance, but make your mental health concerns known immediately. Your GP can review whether Mounjaro is contributing, assess for depression or anxiety requiring treatment, and help you decide whether to continue, pause, or adjust your medication.
Can I take antidepressants or anti-anxiety medications while on Mounjaro?
Yes, many people take mental health medications alongside Mounjaro. Inform your prescriber of all medications and supplements you're taking. Some antidepressants and anti-anxiety drugs may interact with Mounjaro or be affected by its effects on digestion, so your GP will advise on the safest combination and appropriate monitoring.
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