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 Mood Swings — What You Need to Know
Mood changes are not listed as a common side effect of Mounjaro in UK clinical trials, though some people report emotional shifts during treatment. This guide explains what research shows about Mounjaro and mood, how to access it in the UK via NHS or private prescription, typical costs, and what the consultation process involves. Whether you're considering Mounjaro or tirzepatide through a specialist service or private online prescription, understanding both the medication profile and access options helps you make an informed decision alongside your GP or prescriber.
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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.
Mood Changes with Mounjaro — What Clinical Evidence Shows
Mood swings are not listed as a common or very common side effect of Mounjaro (tirzepatide) in official UK product information. In the SURMOUNT clinical trials, mood-related adverse events were rare and not significantly different from placebo. However, some individual reports suggest mood changes, irritability, or emotional shifts during Mounjaro treatment — though these may be secondary to gradual weight management, changes in appetite, or underlying health conditions rather than the medication directly.
Potential mood-related factors include:
- Rapid lifestyle and dietary changes
- Energy changes from reduced calorie intake
- Blood sugar stabilisation (particularly if you have prediabetes)
- Social or emotional responses to weight loss
- Interaction with other medications or pre-existing mental health conditions
If you experience persistent mood changes while taking Mounjaro, inform your prescriber immediately — they can assess whether this relates to the medication or other factors and adjust your treatment plan accordingly.
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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.
Accessing Mounjaro in the UK — NHS vs Private Routes & Costs
In the UK, Mounjaro access differs significantly between NHS and private options. NHS access: Available through tier 3 specialist weight management services following GP referral, though availability and waiting times vary considerably by region (ICB). Private access: Available through UK-licensed online prescribing services following a remote clinical assessment — typically faster but at a cost of approximately £150–£300 per month depending on your dose (ranging from 2.5 mg to 15 mg via the KwikPen delivery system). Consultations assess your BMI, health history, and suitability before issuing a prescription to a GPhC-registered pharmacy. Use our GLP-1 weight loss calculator to explore potential outcomes before committing.
The online consultation process is straightforward: complete a medical questionnaire, have a video or phone consultation with a UK-licensed prescriber, receive a prescription if approved, and collect your medication from a registered pharmacy. Most private consultations cost £20–£50. Costs vary based on your starting dose — initial doses (2.5–5 mg) are typically cheaper than maintenance doses (10–15 mg). Always check whether your chosen provider offers dose escalation support and ongoing monitoring, as Mounjaro requires regular dose increases over several months. Some services include follow-up consultations in their pricing; others charge per consultation.
- 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 mood change a listed side effect of Mounjaro in the UK?
Mood swings are not listed as a common side effect in UK product information or clinical trial data. However, some individuals report emotional changes during treatment, which may relate to gradual weight management, dietary changes, or blood sugar stabilisation rather than tirzepatide directly. Always report mood changes to your prescriber.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £150–£300 per month depending on your dose and provider. Initial doses (2.5–5 mg) are usually cheaper than maintenance doses (10–15 mg). Consultation fees are typically £20–£50 additional. Prices vary by service, so compare providers before choosing.
Can I get Mounjaro through the NHS in the UK?
Yes, Mounjaro is available through NHS tier 3 specialist weight management services following a GP referral. However, availability and waiting times vary significantly by region. Your GP can refer you if you meet eligibility criteria (BMI ≥30 or ≥27 with weight-related health conditions).
What happens during a private Mounjaro consultation?
You'll complete a medical questionnaire, have a consultation with a UK-licensed prescriber (video or phone), discuss your health history and weight loss goals, and receive a prescription if approved. The prescriber assesses your suitability based on your BMI, medical conditions, and current medications before issuing the Mounjaro prescription.
Does private Mounjaro include ongoing support?
Support varies by provider. Some include follow-up consultations and dose escalation guidance in their pricing; others charge separately for each consultation. Ask your chosen service about ongoing support, dose escalation plans, and how they monitor side effects or mood changes during 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.