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 Twice A Week?
Mounjaro (tirzepatide) is a prescription-only weight management injection licensed in the UK for once-weekly use only. Taking Mounjaro twice a week is not recommended and is outside the approved dosing schedule. The standard UK prescribing protocol involves one 2.5mg to 15mg injection once weekly, with dose increases every four weeks if clinically appropriate. If you're considering changes to your Mounjaro schedule, always discuss this with your GP or the prescriber managing your treatment. Our free GLP-1 weight loss calculator can help you understand typical weight loss expectations with standard dosing.
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.
Mounjaro Dosing Schedule — What The NHS Approves
Mounjaro's approved UK dosing is strictly once weekly. The MHRA-licensed prescribing information specifies a once-weekly injection schedule with a minimum of seven days between doses. The dose titration protocol is: 2.5mg (weeks 1–4), 5mg (weeks 5–8), 7.5mg (weeks 9–12), 10mg (weeks 13–16), 12.5mg (weeks 17–20), and 15mg maximum (week 21 onwards). Each Mounjaro KwikPen contains four doses for four weeks' supply. Taking Mounjaro twice weekly would mean shortening the interval between injections, which is not supported by clinical evidence or UK regulatory approval. The SURMOUNT clinical trials that established Mounjaro's safety and efficacy were conducted using the once-weekly schedule. NHS specialist weight management services and private prescribers in the UK both follow this once-weekly protocol because it reflects the licensed dosing regimen.
- Minimum interval between doses: 7 days (one week)
- Licensed maximum frequency: once weekly
- Dose range: 2.5mg to 15mg once weekly
- Dose adjustments: every 4 weeks minimum
- Any changes must be discussed with your prescriber
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.
Why Twice-Weekly Dosing Isn't Approved In The UK
Taking Mounjaro more frequently than once weekly increases the risk of adverse effects without additional clinical benefit. Tirzepatide accumulates in your system with a half-life of around five days, meaning once-weekly dosing provides adequate steady-state levels for appetite suppression and metabolic effects. Doubling the frequency would increase drug concentration significantly, raising the risk of gastrointestinal side effects (nausea, vomiting, diarrhoea), injection site reactions, and other complications. The MHRA has not approved twice-weekly dosing because it falls outside the evidence base from the SURMOUNT trials. If standard once-weekly dosing isn't delivering expected results, your prescriber may increase the dose at your next scheduled injection (minimum four weeks later) rather than shorten the injection interval. Always speak with your GP or healthcare provider before making any changes to your Mounjaro schedule—never adjust dosing independently.
- 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 it safe to take Mounjaro more frequently than once a week?
No. Mounjaro is licensed for once-weekly use only in the UK. Taking it more frequently is not approved by the MHRA and increases the risk of side effects without additional benefit. Tirzepatide accumulates in your body, so more frequent dosing could lead to dangerous drug levels. Always follow your prescriber's instructions exactly.
What should I do if I feel Mounjaro isn't working at once-weekly dosing?
If you're not seeing expected results, discuss this with your prescriber at your next review. They may increase your dose (from 5mg to 7.5mg, for example) at your next injection, or investigate other factors affecting weight loss, such as diet or underlying health conditions. Never change your dosing schedule without medical guidance.
Can I take Mounjaro every five days instead of seven?
No. The minimum interval between Mounjaro injections is seven days (one week). Shortening this interval is not licensed and increases side effect risk. The once-weekly schedule is based on the drug's half-life and the clinical trial evidence that supports its safety and effectiveness.
What happens if I accidentally take Mounjaro twice in one week?
Contact your prescriber or NHS 111 immediately for guidance. Do not take your next scheduled dose as planned—wait the full seven days from your most recent injection. Your prescriber may advise on monitoring for side effects. Accidental double dosing can increase nausea, vomiting, and other gastrointestinal symptoms.
Is there a different weight loss injection I could take more frequently?
Saxenda (liraglutide) is a GLP-1 injection licensed in the UK for daily use, offering a different schedule option. Wegovy (semaglutide) is also once-weekly like Mounjaro. Speak with your GP or prescriber about which option might suit your needs best. Each medication has different profiles, side effects, and dosing routines.
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.