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
Why 2.5 Mg Mounjaro Might Not Be Working for You
If you're taking 2.5 mg Mounjaro and not seeing results, you're likely still in the starting phase—this is the lowest dose and is designed for adjustment, not weight loss. Mounjaro follows a specific dose titration schedule over several weeks, and at 2.5 mg, your body is still adapting to the medication. This guide explains what's normal, when to expect results, and how to access Mounjaro in the UK through both NHS and private routes, including typical costs and the clinical assessment process.
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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.
Understanding 2.5 Mg and Dose Titration in the UK
The 2.5 mg Mounjaro dose is always the starting dose only—it's not intended to produce significant weight loss. Mounjaro works through a careful dose titration schedule, where your dose increases every 4 weeks if tolerated well. At 2.5 mg (weeks 1–4), most people experience adjustment side effects like nausea or mild appetite reduction, but substantial weight loss typically doesn't begin until you reach higher maintenance doses (5 mg or above).
In clinical trials (SURMOUNT-1), average weight loss results were:
- 5 mg: approximately clinically studied weight loss
- 10 mg: approximately clinically studied weight loss
- 15 mg (maximum): approximately clinically studied weight loss
Results vary considerably between individuals. If you're only a few weeks into 2.5 mg, weight loss may not yet be noticeable. Your prescriber will assess whether it's appropriate to escalate your dose after the standard 4-week period at each level. The tirzepatide (active ingredient) in your Mounjaro KwikPen is still working on appetite and metabolism even at the starter dose—dose escalation is the next step if tolerated.
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.
UK Access Routes: NHS vs Private Cost and Process
NHS access: Mounjaro is now approved by NICE for NHS specialist weight management services. However, access is limited to specialist tier 3/4 services (not routine GP prescription), and eligibility requires referral from your GP. Waiting times vary significantly by region—some areas have waits of 6–18 months. If you qualify under NHS criteria (BMI ≥30, or BMI ≥27.5 with weight-related health conditions), ask your GP about local NHS specialist services.
Private access: You can obtain a Mounjaro prescription privately through an online clinical consultation with a UK-licensed prescriber. Costs typically range from £150–£320 per month depending on dose and provider. The assessment takes 10–20 minutes; if approved, your prescription is dispensed by a GPhC-registered pharmacy. No NHS referral needed. This route gives faster access but is self-funded. Use our free GLP-1 weight loss calculator to explore projected outcomes at different doses, and our BMI calculator to check your eligibility context.
- 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 2.5 mg Mounjaro supposed to work for weight loss?
No—2.5 mg is a starting/adjustment dose only, designed to help your body tolerate the medication. Meaningful weight loss typically begins at 5 mg and increases at higher doses (10 mg, 15 mg). Stay at 2.5 mg for the recommended 4 weeks, then your prescriber will assess whether to increase your dose.
When should I see weight loss results on Mounjaro in the UK?
Results usually become noticeable between weeks 4–12, typically once you've reached 5 mg or higher. At 2.5 mg, most people experience appetite reduction but minimal weight loss. Individual timelines vary based on diet, activity, and metabolism. Keep a progress log using our free progress tracker.
How much does Mounjaro cost privately in the UK?
Private Mounjaro costs typically range from £150–£320 per month depending on the dose (2.5 mg to 15 mg) and the provider. Each Mounjaro KwikPen contains 4 weeks of doses. Prices vary between online prescribing services—compare options via online consultation.
Can I get Mounjaro on the NHS for weight management in the UK?
Yes, NICE has approved tirzepatide for NHS specialist weight management services. However, you must be referred by your GP to a tier 3/4 specialist service, eligibility criteria apply (BMI ≥30 or ≥27.5 with health conditions), and waiting lists are long in many areas. Ask your GP about local NHS weight management services.
What should I do if Mounjaro at 2.5 mg isn't working?
First, confirm you're in the adjustment phase (typically 4 weeks). If nausea or side effects are severe, speak to your prescriber—they may slow escalation. After 4 weeks, discuss dose increase to 5 mg with your prescriber. Ensure you're also following a reduced-calorie diet and increasing physical activity, as medication works best alongside lifestyle changes.
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.