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
Can You Take Mounjaro Every 6 Days?
Mounjaro is designed as a once-weekly injection, and taking it every 6 days instead would mean dosing more frequently than prescribed. This is not recommended without explicit guidance from your prescriber. Mounjaro (tirzepatide) is a prescription-only medicine, and any changes to your injection schedule must be discussed with the GP or prescriber managing your treatment. Using the medication outside its approved dosing regimen could affect safety and effectiveness. Always follow the instructions provided with your KwikPen and contact your healthcare provider if you have questions about your injection timing.
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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.
Why Mounjaro Is Once-Weekly, Not Every 6 Days
Mounjaro is formulated as a once-weekly injection, meaning the medication is designed to work over a 7-day cycle. The active ingredient, tirzepatide, has a half-life that supports once-weekly dosing. Clinical trials that established safety and effectiveness, including the SURMOUNT trials, were based on this weekly schedule. Taking Mounjaro every 6 days would mean injecting more frequently than tested, which could lead to:
- Unpredictable medication levels in your bloodstream
- Increased risk of side effects
- Potential overdosing or underdosing effects
- Voiding the medication's safety profile
Your KwikPen is pre-filled for weekly use, with each pen containing exactly 4 weeks of doses. The timing is built into the pen design and the prescribing guidance. If you're struggling with your injection schedule or considering changing it, speak to your GP or prescriber rather than altering the dosing yourself.
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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.
What to Do If You're Considering a Schedule Change
If you're thinking about taking Mounjaro every 6 days, there's usually an underlying reason — perhaps you feel side effects wearing off, or you're hoping to speed up weight loss. These conversations belong with your prescriber, not with self-adjustment. Your GP can discuss dose escalation if appropriate, which is the safe, evidence-based way to increase Mounjaro's effect. Use our free GLP-1 weight loss calculator to track your progress and discuss realistic timelines with your prescriber. If you accidentally miss or delay a dose, the guidance is clear: if fewer than 4 days have passed, inject as soon as you remember; if more than 4 days have passed, skip and return to your normal schedule. Never try to "catch up" with extra 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.
What if I miss my Mounjaro injection by one day?
If you miss your weekly injection by 1 day (injecting on day 8 instead of day 7), this is generally acceptable. As long as you inject within 4 days of your scheduled date, you can inject as soon as you remember and continue your normal weekly schedule from there. Always inform your prescriber if you're consistently missing doses.
Is there any situation where Mounjaro can be injected more frequently?
No. Mounjaro is only prescribed as a once-weekly injection. Any changes to dosing frequency must be approved by your prescriber in writing. Attempting to inject more frequently on your own is unsafe and not supported by clinical evidence or UK licensing.
Can I take Mounjaro every 8 or 9 days instead of weekly?
You should not alter the injection schedule without prescriber approval. If you're finding weekly injections difficult, discuss alternative arrangements with your GP — they may suggest adjusting your injection day to a time that suits you better, but the 7-day interval must be maintained.
What's the difference between Mounjaro and Wegovy dosing schedules?
Both Mounjaro and Wegovy are once-weekly injections. Mounjaro (tirzepatide) doses range from 2.5 mg to 15 mg weekly. Wegovy (semaglutide) doses range from 0.25 mg to 2.4 mg weekly. Neither should be taken more frequently than once per week without explicit prescriber guidance.
If I want faster weight loss, should I inject Mounjaro more often?
No. Faster injection schedules are not safer or more effective — they're actually riskier. If you want to accelerate results, the evidence-based approach is to discuss dose escalation with your prescriber. Our weight loss calculator can help you track realistic progress and discuss options with your GP or weight management specialist.
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.