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 Low Mood — What You Should Know
If you're considering Mounjaro (tirzepatide) for weight management in the UK, it's important to understand how it might affect your mood and mental health. While most people tolerate this GLP-1 and GIP receptor agonist well, some individuals have reported mood changes during treatment. This guide explains what NHS guidance says, what clinical evidence shows, and when to contact your GP. Understanding potential side effects helps you make an informed decision about whether Mounjaro is right for you.
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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.
Mounjaro, Mood Changes, and NHS Evidence
Mounjaro is a prescription-only weight management injection licensed in the UK for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or heart disease. In clinical trials, some people reported mood changes including low mood, anxiety, or depression, though these were not the most common side effects. The SURMOUNT trials, which led to Mounjaro's UK approval, recorded mood disturbances in a small percentage of users — but it's important to note that weight loss itself can sometimes trigger emotional changes as people adjust to lifestyle modifications.
- Very common side effects: nausea, diarrhoea, constipation, stomach pain (affecting more than 1 in 10 people)
- Mood-related reports: less frequent but documented — low mood, anxiety, or emotional changes reported by some users
- Context matters: gradual weight management and major lifestyle changes can independently affect mood, making it difficult to isolate whether changes are medication-related or adjustment-related
- NHS assessment: your GP or specialist prescriber will assess your mental health history before starting Mounjaro via your NHS tier 3 weight management service
If you have a history of depression, anxiety, or other mental health conditions, inform your prescriber before starting treatment. Never stop Mounjaro suddenly — always speak to your GP or prescriber first if you experience mood changes.
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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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Managing Mood on Mounjaro — NHS and Private Routes
In the UK, Mounjaro is accessed either through NHS specialist tier 3 weight management services or via private online prescribing following a clinical assessment. NHS prescribers will ask about your mental health history before starting treatment — this is standard practice. If you experience low mood, anxiety, or emotional changes while on Mounjaro, contact your GP immediately rather than stopping the injection yourself. Your prescriber may adjust your dose, offer mental health support, or recommend stopping treatment safely.
- Report any mood changes to your GP or prescriber promptly
- Do not stop Mounjaro suddenly — risk of rebound effects
- Mental health support is available through NHS — ask your GP about counselling or therapy
- Keep a mood diary if helpful — note changes and when they started
- Use our free GLP-1 weight loss calculator to understand projected outcomes — realistic expectations can help reduce anxiety about results
- 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.
Can Mounjaro cause depression or low mood?
In clinical trials, some people reported mood changes including low mood and anxiety, though these were not among the most common side effects. Very common side effects were nausea, diarrhoea, and constipation. However, gradual weight management and lifestyle changes can independently affect mood. If you experience persistent low mood, contact your GP immediately.
Should I tell my GP if I have a history of depression before starting Mounjaro?
Yes, absolutely. Always inform your prescriber of any mental health history, including depression, anxiety, or other conditions. NHS specialists and private prescribers assess your mental health before starting Mounjaro. This helps them monitor you more carefully and decide whether treatment is appropriate for you.
What should I do if I feel low mood after starting Mounjaro?
Contact your GP or prescriber promptly — do not stop the injection yourself. They may adjust your dose, offer support, recommend stopping gradually, or refer you to mental health services. Mood changes can be addressed with proper support and monitoring, so seeking help early is important.
Is low mood more common with Mounjaro than with Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are GLP-1 based medications with similar side effect profiles. Mood changes are reported with both but are not among the most common side effects. Individual experiences vary greatly. Your prescriber can discuss which medication may be more suitable for your specific health situation.
Can I take Mounjaro if I'm on antidepressants?
Mounjaro can be used alongside antidepressants, but you must inform your prescriber of all medications you take. Mounjaro may affect how quickly some oral medications are absorbed, so your GP may need to monitor you more closely. Always declare all mental health medications during your clinical assessment.
Ready to take control of your weight loss journey?
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