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
Mounjaro Kwikpen 2.5 mg — Starting Dose Explained
The Mounjaro Kwikpen 2.5 mg is the starting dose for tirzepatide, a prescription-only weight management injection licensed in the UK. This initial dose is designed to help your body adjust to the medication before gradual escalation to higher doses. Understanding what to expect during these first four weeks can help you prepare for your weight management journey. Use our free GLP-1 weight loss calculator to explore how tirzepatide may support your goals, alongside dietary changes and physical activity.
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 the 2.5 mg Starting Dose Works
The Mounjaro Kwikpen 2.5 mg contains a dual GIP and GLP-1 receptor agonist — tirzepatide — which works differently from single-action GLP-1 medications like Wegovy (semaglutide). This dual mechanism may help regulate appetite, reduce food cravings, and support feeling fuller after smaller meals. The 2.5 mg dose is a starting point; you'll typically remain on this dose for weeks 1–4 before your prescriber considers escalating you to 5 mg if appropriate.
What each Kwikpen contains:
- One Kwikpen = 4 weekly injections (4 weeks supply)
- Each injection = 2.5 mg tirzepatide
- Injected once per week, same day each week
- Pre-filled and ready to use — no mixing required
The 2.5 mg dose allows your body to adapt to the medication's effects, helping minimise side effects as you adjust.
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.
Eligibility and What to Expect at 2.5 mg
In the UK, Mounjaro may be prescribed for adults with a BMI of 30 kg/m² or above, or BMI 27–29.9 kg/m² with weight-related health conditions such as type 2 diabetes, high blood pressure, or sleep apnoea. Lower BMI thresholds apply for people of South Asian, Chinese, Black African, or Black Caribbean heritage.
During weeks 1–4 on 2.5 mg, you may experience nausea, mild stomach discomfort, or changes in appetite — these are common as your body adjusts. Keep your prescriber informed of any side effects. Use our free BMI calculator to monitor how your current weight relates to NHS healthy weight thresholds, and track your progress with our weight loss tracker as you begin 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.
How is Mounjaro 2.5 mg injected?
Using the pre-filled KwikPen, you inject 2.5 mg under the skin once per week. Common injection sites include the stomach (abdomen), upper thigh, or upper arm. Rotate sites each week. The pen is designed for self-injection and takes seconds to administer.
Why start at 2.5 mg and not a higher dose?
The 2.5 mg starting dose allows your body to tolerate tirzepatide gradually. This reduces the risk of severe side effects and helps your prescriber assess how you respond before escalating to 5 mg (typically after 4 weeks) and beyond.
Can I stay on 2.5 mg indefinitely?
The 2.5 mg dose is intended as a starting point, not a maintenance dose. Most patients progress to higher doses (5 mg, 7.5 mg, 10 mg, 12.5 mg, or 15 mg) based on their response and tolerability. Your prescriber will guide escalation.
Is Mounjaro 2.5 mg available on the NHS?
NICE has approved tirzepatide (Mounjaro) for NHS specialist weight management services. However, NHS access varies by region and availability may be limited. Private prescription is available through online UK-licensed prescribers following clinical assessment.
How does Mounjaro 2.5 mg compare to Wegovy's starting dose?
Mounjaro starts at 2.5 mg (tirzepatide, dual GIP/GLP-1), while Wegovy starts at 0.25 mg (semaglutide, GLP-1 only). Mounjaro's dual mechanism may produce different results, though individual responses vary. Your prescriber will advise which is appropriate for you.
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.