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's the Difference Between 2.5mg and 5mg Mounjaro?
Mounjaro (tirzepatide) is prescribed in escalating doses starting at 2.5mg and increasing to 5mg after four weeks. The 2.5mg dose is an adjustment dose to help your body adapt to the medication, while 5mg is typically the first maintenance dose where clinical effects become more noticeable. Both are prescription-only doses that require clinical assessment and ongoing monitoring from your prescriber. Individual responses vary significantly between users.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
How Mounjaro Dose Titration Works
Mounjaro follows a structured dose titration schedule designed to minimise side effects and allow your body to adapt gradually. You start on 2.5mg once weekly for weeks 1–4, then escalate to 5mg for weeks 5–8. Each dose is delivered via a pre-filled KwikPen auto-injector, and you must spend at least four weeks on each dose level before increasing further. The 2.5mg starting dose is sometimes called the "adjustment dose" because it's not typically where weight loss benefits become apparent—it's primarily to help your body tolerate the medication. At 5mg, most users begin to experience more significant appetite reduction and the clinical effects measured in weight loss trials.
- 2.5mg (weeks 1–4): Adjustment phase, minimal side effects expected
- 5mg (weeks 5–8+): First maintenance dose, more noticeable appetite suppression
- Higher doses (7.5mg, 10mg, 12.5mg, 15mg): Available if needed for additional effect
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Weight Loss and Side Effects: 2.5mg vs 5mg
Clinical evidence from the SURMOUNT trials showed that weight loss becomes more apparent at higher doses. At 5mg, most users report noticeably reduced appetite compared to the 2.5mg starting phase. However, side effects like nausea, diarrhoea, and constipation also tend to increase with dose escalation. The 2.5mg dose may cause mild gastrointestinal effects in some users, but these often settle within the first few weeks. Moving to 5mg can temporarily increase symptoms as your body adjusts, though most side effects improve over time. Your prescriber will monitor your tolerance and may recommend staying at 5mg longer before further escalation if needed. Use our free GLP-1 weight loss calculator to explore potential weight loss projections at different tirzepatide doses.
- 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 2.5mg Mounjaro enough for weight loss?
The 2.5mg dose is an adjustment dose, not a therapeutic dose. Weight loss effects are typically minimal at 2.5mg—it's designed to help your body adapt. Clinical benefits usually become apparent at 5mg and above. Your prescriber will guide you through the escalation schedule based on your tolerance and response.
Why do I have to wait four weeks between doses?
The four-week interval allows your body to reach a steady state with each dose and helps identify any side effects. This gradual approach minimises nausea and gastrointestinal upset. Rushing the titration schedule increases the risk of intolerable side effects and is not recommended.
Can I stay on 2.5mg if it's working for me?
If you're experiencing weight loss on 2.5mg alone, this would be unusual but possible in some individuals. However, you should discuss your response with your prescriber. Most clinical benefits are seen at 5mg and above. Your prescriber may recommend continuing escalation or staying at 2.5mg depending on your personal health factors.
What happens if I skip from 2.5mg straight to 7.5mg?
Skipping doses is not recommended. The titration schedule is designed for safety and tolerability. Jumping to a higher dose significantly increases the risk of severe nausea, vomiting, and other side effects. Always follow your prescriber's guidance on dose escalation timing.
How long does it take to feel a difference between 2.5mg and 5mg?
Most users notice a more pronounced appetite reduction within 1–2 weeks of starting 5mg. However, individual responses vary. Some people experience immediate changes, while others take longer to adapt. Weight loss itself typically becomes measurable within 4–8 weeks at therapeutic doses like 5mg.
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.