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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Can Mounjaro Cause Depression? Comparing Mounjaro and Wegovy
Depression and mood changes are not listed as common side effects of Mounjaro or Wegovy in UK clinical trials, though both medications can affect mood indirectly through weight loss and appetite changes. This guide compares how Mounjaro (tirzepatide) and Wegovy (semaglutide) affect mental health based on SURMOUNT and STEP trial data, prescriber experience in the UK, and NHS guidance. If you have concerns about mood changes while taking either medication, always speak to your GP or prescriber immediately.
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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.
Clinical Trial Data: Depression Risk in SURMOUNT vs STEP
Mounjaro (tirzepatide) in SURMOUNT trials: Depression was not reported as a common adverse event in SURMOUNT-1, SURMOUNT-2, or SURMOUNT-4. Mood disturbance occurs very rarely and is not listed in the standard side effects profile. The dual GIP and GLP-1 mechanism does not appear to increase depression risk compared to GLP-1 alone.
Wegovy (semaglutide) in STEP trials: Similarly, depression was not a frequently reported side effect in STEP-1, STEP-2, STEP-3, or STEP-4. Psychiatric adverse events were uncommon, occurring in less than 1% of trial participants at standard doses.
Important context: Both medications can indirectly affect mood through gradual weight management, reduced appetite, and changes in energy levels. Nausea, diarrhoea, and fatigue — common early side effects — may temporarily lower mood. These typically improve as the body adjusts over 4–8 weeks.
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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.
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Individual Factors and Prescriber Considerations
Depression risk depends on your individual medical history rather than the medication itself. If you have a personal or family history of depression, bipolar disorder, or other mental health conditions, your UK prescriber will assess whether Mounjaro or Wegovy is appropriate for you during your clinical consultation. Both medications undergo the same eligibility assessment — there is no significant difference between them in terms of psychiatric safety.
Weight loss itself often improves mood and mental health in people living with obesity, as it reduces health anxiety, improves mobility, and increases confidence. However, gradual weight management or unpleasant gastrointestinal side effects may temporarily affect mood. If you experience persistent low mood, anxiety, or suicidal thoughts whilst taking either medication, contact your GP or the Samaritans immediately (116 123).
- 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.
Does Mounjaro cause depression more than Wegovy?
No. Clinical trials show neither medication has a higher depression risk. Both are GLP-1 pathway medications (Mounjaro is dual GIP+GLP-1, Wegovy is GLP-1 only). Depression is not a common side effect of either. Your prescriber assesses your individual psychiatric history to determine suitability.
What mood-related side effects are actually reported with Mounjaro?
Mood changes are not listed as common side effects. Fatigue (low energy) is common, which may temporarily affect mood. Nausea and gastrointestinal upset can contribute to feeling unwell. These typically improve within 4–8 weeks as your body adjusts to the medication.
Can weight loss injections help depression?
Weight loss itself often improves mood and mental wellbeing by reducing health anxiety, improving mobility, and boosting confidence. However, if you have pre-existing depression, your GP should assess whether these medications are suitable for you before starting treatment.
What should I do if I feel depressed whilst taking Mounjaro or Wegovy?
Contact your GP or prescriber immediately. Do not stop taking the medication without medical advice. If you experience suicidal thoughts, call the Samaritans (116 123) or your local emergency services. Mental health changes should always be reported to your healthcare provider.
How do I check if Mounjaro or Wegovy is right for me?
Both medications require a clinical assessment by a UK-licensed prescriber who will review your medical history, current medications, and mental health status. Use our free GLP-1 weight loss calculator to explore potential outcomes, and discuss suitability with your GP or private prescriber before starting treatment. ```
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