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 Use Mounjaro With HRT?
Yes, you can typically use Mounjaro (tirzepatide) alongside hormone replacement therapy (HRT), but it requires careful monitoring and open communication with your GP or prescriber. Mounjaro does not directly interact with HRT hormones, but both medicines affect how your body absorbs other medications, so your healthcare team needs to know about both treatments. This guide covers UK prescribing context, what to tell your GP, and monitoring requirements.
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.
What You Need to Tell Your Prescriber About HRT
If you are taking HRT (whether oestrogen, progesterone, or combined hormone replacement) and considering Mounjaro (tirzepatide), your prescriber must know about your HRT before issuing a prescription. The reason is not direct drug-to-drug interaction — tirzepatide and HRT hormones do not chemically interfere with each other — but rather that Mounjaro slows gastric emptying, which means food (and medications taken with food) stay in your stomach longer.
- HRT tablets taken orally may have slightly altered absorption patterns when you start Mounjaro
- Some HRT users report changes in symptom control when starting weight loss injections, though this is usually temporary during dose adjustment
- Patches and other non-oral HRT formulations are not affected by Mounjaro's gastric effects
- Your prescriber may recommend spacing out your HRT tablet dose away from meals to optimise absorption if you are taking oral HRT
Always inform your GP or the prescriber conducting your online assessment that you are on HRT — this is essential information for your safety record and allows them to provide personalised guidance.
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.
NHS Guidance and Monitoring Requirements
Under NHS guidance, if you are prescribed Mounjaro through a tier 3 specialist weight management service, your GP will be informed of the prescription. This means your medical record will show both your HRT and Mounjaro use, and your GP can flag any concerns. MHRA-approved tirzepatide does not carry specific contraindications against HRT use, but good prescribing practice requires baseline health checks.
- Your GP should assess your menopausal symptoms and HRT efficacy at baseline and periodically during Mounjaro treatment
- Weight loss itself can affect HRT absorption and symptom control — your dose may need adjustment
- Report any changes to hot flushes, night sweats, mood, or HRT symptom control to your GP
- Keep both your weight management team and GP in communication about your treatment plan
Use our free BMI calculator above to check your current BMI and understand your eligibility for weight management support under NHS criteria. If you are eligible for Mounjaro, your prescriber will assess the full picture of your health, including HRT use.
- 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.
Does Mounjaro interfere with HRT hormone absorption?
Not directly. Mounjaro does not chemically interfere with oestrogen or progesterone hormones. However, because it slows stomach emptying, oral HRT tablets may be absorbed slightly differently. This is usually not clinically significant, but your prescriber should know you are on HRT to monitor symptom control.
Will Mounjaro affect my menopausal symptoms if I'm on HRT?
Mounjaro itself does not typically worsen menopausal symptoms. However, weight loss (which Mounjaro supports) can sometimes affect HRT efficacy — some people need HRT dose adjustment. Report any changes in hot flushes, night sweats, or mood to your GP for review.
What should I tell my GP or prescriber about HRT before starting Mounjaro?
Tell them the type of HRT you are taking (oral tablet, patch, gel, etc.), the dose, how long you have been on it, and how well it controls your symptoms. Also mention any recent changes to your symptoms. This helps them prescribe Mounjaro safely and monitor your overall health.
Can I take my HRT tablet at the same time as Mounjaro injection?
You do not take Mounjaro as a daily tablet — it is a once-weekly injection. Your HRT tablet schedule does not need to change. However, if your prescriber advises spacing meals and medications, you can take your HRT tablet with water independently of food timing.
Where can I get Mounjaro if I am on HRT in the UK?
Through NHS tier 3 specialist weight management services (via GP referral) or through private online prescribing with a UK-licensed prescriber. Either route requires a clinical assessment where you disclose your HRT use. Your prescriber will determine suitability based on your full health picture, including HRT use.
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.