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
What Happens When You Increase Your Mounjaro Dose?
When starting tirzepatide (Mounjaro), your prescriber will increase your dose gradually over several weeks. Most people experience side effects during dose escalation, particularly in the first week after each increase. Understanding what to expect can help you manage symptoms and stay on track with treatment. This guide explains the dose titration process, common side effects at each stage, and practical tips for managing them during your weight loss journey.
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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 Dose Escalation and Side Effects Timeline
Mounjaro uses a structured dose titration schedule, with increases every 4 weeks. Each dose step may trigger temporary side effects as your body adjusts to the medication.
- 2.5 mg (weeks 1–4): Starting dose. Nausea and appetite suppression are most common. Many people experience mild stomach discomfort.
- 5 mg (weeks 5–8): First escalation. Side effects often intensify temporarily, then improve by week 3–4. Diarrhoea and constipation may alternate.
- 7.5 mg onwards: Higher doses increase nausea risk in the first 7–10 days post-injection, but typically settle by day 14. Vomiting and appetite loss are more pronounced than at lower doses.
- Key pattern: Most side effects peak within days 1–3 of each injection, then improve significantly by day 7–10.
Your prescriber may delay escalation if side effects are severe, or recommend staying at your current dose longer. Use our GLP-1 weight loss calculator to understand what typical weight loss looks like at each dose level.
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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
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Managing Side Effects During Dose Increases
Practical strategies to reduce discomfort: Eat small, frequent meals rather than large portions—this eases nausea and prevents stomach pain. Avoid fatty, greasy, or spicy foods for 2–3 days after injection. Stay hydrated with small sips of water throughout the day, not large amounts at once. Ginger tea, peppermint, or anti-nausea medications (discuss with your GP) can help.
If side effects are severe—persistent vomiting, inability to keep fluids down, severe stomach pain spreading to your back—contact your prescriber or GP immediately. These could signal pancreatitis or other complications. Most people find side effects become manageable by week 2–3 of each dose level. Track your symptoms with our free progress tracker to spot patterns and inform your prescriber.
- 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.
Why do side effects get worse when I increase my Mounjaro dose?
Your body is adjusting to a higher concentration of the medication. GLP-1 and GIP receptor activation intensifies at higher doses, increasing effects on stomach emptying and appetite. This is temporary—most people adapt within 7–14 days as your body becomes accustomed to the new dose level.
Should I stop increasing my Mounjaro dose if side effects are bad?
No—do not stop on your own. Contact your prescriber instead. They may delay your next increase, keep you on your current dose longer, or recommend additional support (anti-nausea medication, dietary adjustments). Stopping abruptly can affect your weight loss results and is not advised.
Which Mounjaro dose causes the worst side effects?
There is no single "worst" dose—side effects vary by individual. Generally, the 5 mg step causes noticeable effects in most people, and 10 mg and above intensify nausea in the first few days. Some people have minimal side effects throughout; others struggle more. Your prescriber monitors this closely.
How long do side effects last after increasing Mounjaro?
Most side effects peak within 3 days of injection, then improve significantly by day 7–10. Nausea, diarrhoea, and appetite suppression usually settle within 2 weeks of dose increase. If symptoms persist beyond 2 weeks, inform your prescriber—this may signal you need a longer adjustment period.
Can I access Mounjaro through the NHS if side effects are severe?
NHS access depends on your local ICB and specialist weight management service availability. Private prescription is often faster—you can consult a UK-licensed prescriber online, who will assess whether to continue, pause, or switch your treatment. Your GP can also discuss NHS options and provide support managing side effects regardless of how you access the medication.
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.