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 at Mounjaro Week 6?
At week 6, you'll typically be on the 5mg maintenance dose of Mounjaro after completing the initial 2.5mg starting phase. This is the first standard dose used in NHS and private UK prescribing. Most people experience reduced appetite and earlier fullness during meals by this stage. Side effects like nausea often begin to ease as your body adjusts. Week 6 marks an important checkpoint — your prescriber will assess how well you're tolerating the medication before any potential dose increase to 7.5mg. Use our free GLP-1 weight loss calculator to project potential outcomes with your current dose.
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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.
Mounjaro Dosing Schedule in UK Practice
Mounjaro follows a strict 4-week titration schedule approved by the MHRA for UK prescribing. At week 6, you're in your second week on the 5mg dose. Here's how UK dosing typically progresses:
- Weeks 1–4: 2.5mg weekly injection (starting/adjustment dose)
- Weeks 5–8: 5mg weekly injection (first maintenance dose)
- Weeks 9–12: 7.5mg (if escalation needed)
- Weeks 13–16: 10mg (further escalation)
- Week 17+: Up to 15mg maximum dose
Your GP or specialist must confirm you're tolerating each dose for at least 4 weeks before increasing. At week 6, you remain on 5mg unless your prescriber has specifically advised otherwise. Individual NHS tier 3 services and private prescribers follow this same MHRA-approved schedule. The tirzepatide formulation works as a dual GIP and GLP-1 agonist, which may explain why many people notice appetite suppression starting to become noticeable by week 6.
Clinically BackedWeight Loss
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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
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Side Effects and Tolerability at Week 6
By week 6, initial gastrointestinal side effects like nausea often improve as your body adjusts to the 5mg dose. However, some people continue to experience stomach discomfort, constipation, or diarrhoea. Staying hydrated and eating smaller, nutrient-dense meals typically helps. If side effects are severe or worsening, contact your prescriber — they may recommend remaining on 5mg for longer before escalating, or temporarily pausing treatment. Weight loss outcomes vary significantly between individuals; clinical trials showed an average of clinically studied weight loss on 5mg after 72 weeks, though results depend heavily on dietary habits and physical activity. Track your progress with our free progress tracker to monitor both side effects and weight changes objectively.
- 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 weight loss be noticeable by week 6?
Weight loss timelines vary. Some people see 1–2kg loss by week 6; others see minimal change. You're still on a lower dose (5mg), and weight loss typically accelerates as dose increases. Consistent dietary changes and physical activity are essential — Mounjaro works best alongside lifestyle modifications, not instead of them.
Should I still feel hungry on 5mg at week 6?
Most people report reduced appetite and earlier fullness on 5mg, but hunger varies individually. If you're experiencing normal appetite, discuss this with your prescriber at week 6. They may recommend staying on 5mg longer or escalating sooner based on your individual response and tolerance.
Can I switch from Mounjaro to Wegovy if I'm not tolerating it at week 6?
Switching between medications is possible but requires GP or prescriber approval. Wegovy (semaglutide) is a single GLP-1 agonist with a different dosing schedule and mechanism. Never switch without clinical guidance. Your prescriber may adjust your Mounjaro dose or suggest alternative approaches first.
Is Mounjaro available through the NHS at week 6?
NHS access to Mounjaro is through tier 3 specialist weight management services, not standard GP prescription. Referral, assessment, and ongoing prescribing happen through your regional specialist service. Availability and waiting times vary significantly by ICB. Private prescribing is available without NHS referral.
What happens if I miss my week 6 injection?
If you miss your week 6 dose, inject within 4 days of the scheduled date and resume your normal schedule the following week. If more than 4 days have passed, skip that dose and take your next injection on your regular day. Never take a double dose. Always inform your prescriber of missed doses.
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.