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
Does Mounjaro Cause Depression or Anxiety?
Mental health concerns are a legitimate question when considering any prescription medication. Neither Mounjaro (tirzepatide) nor Wegovy (semaglutide) list depression or anxiety as confirmed side effects in UK clinical trials. However, some users report mood changes during weight loss treatment. This guide compares the evidence, explains what's known, and clarifies when to speak to your GP. Individual experiences vary, and a prescriber can assess your personal suitability before starting any weight loss injection. Use our GLP-1 weight loss calculator to explore options, then discuss any mental health concerns with your healthcare provider.
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Calculate Your BMI Instantly
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 and Reported Side Effects
The SURMOUNT trials (Mounjaro) and STEP trials (Wegovy) did not identify depression or anxiety as common side effects. In clinical data, nausea, diarrhoea, and stomach pain were the most frequently reported side effects for both medications. However, anecdotal reports on social media and patient forums suggest some individuals experience mood changes — though it's unclear whether this is a direct medication effect, a result of gradual weight management, or unrelated factors.
Mounjaro is a dual GIP and GLP-1 receptor agonist, whilst Wegovy activates GLP-1 only. Both work on brain pathways that regulate appetite and potentially mood. The dual mechanism of Mounjaro theoretically could affect neurotransmitters differently than single-action GLP-1, but clinical evidence does not show depression or anxiety as a class effect. Individual brain chemistry varies significantly, which may explain why some users report mood changes whilst clinical trials do not.
Clinically BackedWeight Loss
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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 You Should Know Before Starting
If you have a history of depression, anxiety, or other mental health conditions, inform your prescriber before starting Mounjaro or Wegovy. They will assess whether the medication is suitable for you and may recommend monitoring. Weight loss itself can affect mood positively (improved confidence, energy, mobility) or sometimes negatively (if weight loss is too rapid or causes nutrient deficiencies).
Some users report feeling "flat" or emotionally numb during treatment — though this is not listed as a standard side effect. If you experience mood changes after starting, contact your GP promptly. Mental health support should continue alongside weight loss treatment. Your prescriber can advise whether to continue, adjust the dose, or switch to an alternative approach. Use our free progress tracker to monitor not just weight, but overall wellbeing during treatment.
- 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 definitely cause depression?
No. Depression is not listed as a confirmed side effect in SURMOUNT clinical trials. Some users report mood changes, but clinical evidence does not establish a direct causal link. Individual experiences vary. If you experience low mood after starting Mounjaro, inform your GP immediately rather than stopping the medication without guidance.
Is Wegovy safer for mental health than Mounjaro?
Both medications have similar mental health profiles in clinical data — neither lists depression or anxiety as common side effects. Wegovy uses a single GLP-1 mechanism, Mounjaro uses dual GIP+GLP-1. There is no evidence that one is safer than the other for mood. Your prescriber will assess your individual suitability based on your medical history.
Can gradual weight management cause anxiety or depression?
Yes, potentially. Very gradual weight management, nutritional deficiencies, or hormonal changes can affect mood. NHS guidance recommends losing weight at 0.5–1 kg per week for sustainable results. Both Mounjaro and Wegovy are designed to support gradual weight loss alongside diet and exercise. Slower, steady progress is generally better for mental wellbeing.
Should I tell my GP about anxiety or depression before starting?
Absolutely. Always inform your GP or prescriber of any mental health history before starting weight loss injections. They will assess your overall suitability, discuss monitoring, and ensure the medication won't interact with any mental health treatments you're already taking (including antidepressants).
What should I do if I feel depressed or anxious after starting?
Contact your GP or prescriber immediately. Do not stop the medication without guidance — they may adjust your dose, recommend additional support, or switch you to an alternative. Mental health changes should be taken seriously and monitored professionally throughout treatment. ```
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.