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
Does Mounjaro Show Up in Blood Tests?
Mounjaro (tirzepatide) will not show up on standard routine blood tests, but it may affect the results you receive. If you're taking this prescription injection as part of your weight management plan, it's important to understand how it influences blood markers — particularly blood sugar, insulin levels, and lipid profiles. Always inform your GP or the healthcare professional ordering your blood tests that you're taking Mounjaro, so they can interpret your results accurately and understand any changes in your health markers.
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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.
How Mounjaro Affects Blood Test Results
Mounjaro won't appear in your blood as a detectable substance, but this dual GIP and GLP-1 receptor agonist actively changes what your blood tests show. The medication works by improving how your body regulates blood sugar and insulin, which means your fasting glucose and insulin levels may be lower than before you started treatment. Your lipid profile (cholesterol and triglycerides) often improves too — a genuine health benefit alongside weight loss.
When you have routine bloods done, inform the phlebotomist and your GP that you're taking Mounjaro. This is especially important if you're also taking diabetes medication — your prescriber may need to adjust doses based on improved blood sugar control. Some patients find their HbA1c drops significantly within weeks of starting Mounjaro, reflecting better long-term glucose management.
- Fasting blood glucose often decreases
- Insulin levels typically improve
- Cholesterol and triglycerides may reduce
- Liver function tests usually remain normal
- Always disclose Mounjaro use before blood work
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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 Your GP Needs to Know
Your GP should have a full picture of your Mounjaro treatment before interpreting any blood results. If you've recently started this UK prescription injection or increased your Mounjaro dose through the titration schedule, significant improvements in metabolic markers are expected and positive. The improved blood sugar control doesn't mean you can stop taking other medications without guidance — your prescriber will assess whether any dose adjustments are needed based on your actual results.
Mounjaro eligibility in the UK is assessed through clinical evaluation, and ongoing blood monitoring is part of responsible prescribing. Regular blood tests help track your response to treatment and ensure the medication is working safely for you. Use our free BMI calculator to understand your baseline, and work with your healthcare team to monitor progress alongside blood work.
- 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 Mounjaro itself show up in a blood test?
No. Mounjaro (tirzepatide) does not appear as a detectable substance in routine blood tests. However, it will change your blood results by improving glucose control, insulin levels, and cholesterol profiles. Your GP needs to know you're taking it to interpret results correctly.
Should I tell my GP I'm taking Mounjaro before blood work?
Yes, always inform your GP and the phlebotomist that you're on Mounjaro before blood tests. This helps them understand changes in your results — particularly improved blood sugar and insulin levels — and ensures any other medications you take are still appropriate for you.
Can Mounjaro affect my diabetes blood test results?
Yes. Mounjaro significantly improves blood sugar control and may lower your HbA1c (three-month glucose average) and fasting glucose levels. If you're also taking diabetes medication like insulin or sulphonylureas, your prescriber may need to adjust doses to avoid low blood sugar.
What blood markers typically improve on Mounjaro?
Common improvements include lower fasting glucose, reduced insulin levels, lower cholesterol and triglycerides, and improved liver function. These changes reflect the medication's positive metabolic effects alongside weight loss from your reduced-calorie diet and increased activity.
How often should I have blood tests while taking Mounjaro?
Your prescriber will advise based on your individual health. Generally, baseline bloods before starting, then periodic monitoring (often every 3–6 months) is recommended, especially if you're also taking diabetes medications or have kidney/liver concerns.
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.