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
How Much Does Mounjaro Increase in September?
If you're taking Mounjaro (tirzepatide) in the UK, your dose may increase in September depending on when you started treatment. Mounjaro requires a structured dose titration schedule, increasing every 4 weeks until you reach an effective maintenance dose. The specific amount you increase to depends on your current dose and how your body is responding to treatment. Your prescriber will guide your personalised dose escalation plan. Use our GLP-1 weight loss calculator to see how different doses may support your weight loss journey.
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.
Understanding Mounjaro Dose Titration Schedule
Mounjaro follows a strict once-weekly dose titration pattern designed to help your body adjust gradually. You must stay on each dose for a minimum of 4 weeks before increasing. The standard escalation pathway is: 2.5 mg (weeks 1–4) → 5 mg (weeks 5–8) → 7.5 mg (weeks 9–12) → 10 mg (weeks 13–16) → 12.5 mg (weeks 17–20) → 15 mg (week 21 onwards). If you started Mounjaro in mid-June, your dose would likely increase in mid-July, mid-August, and potentially in September depending on whether a further escalation is clinically appropriate. Your prescriber may adjust this schedule based on your response and any side effects.
- Each KwikPen contains 4 weeks of doses
- Minimum 4 weeks between dose increases is mandatory
- Maximum dose is 15 mg once weekly
- Individual escalation timelines vary based on start date
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.
What Happens During September Dose Changes?
In September, if your dose is increasing, your prescriber will confirm the next tier is appropriate for you. Before escalating, they consider your weight loss progress, side effects, and overall health. Some people stabilise on 5 mg or 10 mg and don't escalate further — this is normal and appropriate if that dose is working well. Others progress to 15 mg (the maximum). You'll receive a new Mounjaro KwikPen with the updated dose. Store unopened pens in the refrigerator at 2–8°C. If you experience persistent side effects, inform your prescriber before September escalation — they may recommend staying on your current dose longer. Track your progress with our free progress tracker to monitor how each dose is supporting your goals.
- 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.
Will my Mounjaro dose definitely increase in September?
Not necessarily. Dose increases only happen if clinically appropriate for you. Your prescriber assesses whether you're ready to escalate based on your progress, side effects, and health. Some people stabilise on a lower dose. Your prescriber will confirm any September increase in advance.
How much does Mounjaro increase each time?
Mounjaro increases by fixed amounts: from 2.5 mg to 5 mg, then to 7.5 mg, 10 mg, 12.5 mg, and finally 15 mg. Each step up is a specific dose — there are no variable increases. The maximum dose is 15 mg once weekly.
What if I start having side effects in September after my dose increases?
Contact your prescriber immediately. Common side effects include nausea, diarrhoea, and constipation. Your prescriber may recommend staying on your current dose longer, reducing the dose, or managing side effects with dietary adjustments. Never adjust your dose yourself.
Can I delay my September dose increase?
Yes. If you're experiencing side effects or prefer to stabilise on your current dose, discuss this with your prescriber before September. They can adjust your escalation schedule to suit your needs. The dose increase is not mandatory if clinically inappropriate for you.
Is Mounjaro available on the NHS in September 2025?
Mounjaro is available through NHS tier 3 specialist weight management services in some regions, though availability and waiting times vary significantly. Many people access it privately through online prescribing following clinical assessment. Both routes require a prescription from a UK-licensed prescriber.
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.