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
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Does Mounjaro Affect HRT?
If you're taking hormone replacement therapy (HRT) and considering Mounjaro, it's important to understand how these two treatments interact. The short answer is that Mounjaro (tirzepatide) itself does not directly interact with HRT medications, but there are important considerations you should discuss with your GP. This guide covers what research shows, what precautions apply, and how to manage both treatments safely alongside a reduced-calorie diet and increased physical activity.
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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 the Evidence Shows About Mounjaro and HRT
Mounjaro does not have a documented direct drug interaction with HRT medications, according to current UK prescribing information. However, this does not mean there are no considerations. Mounjaro works by activating GIP and GLP-1 receptor pathways to reduce appetite and support weight management—a completely different mechanism from hormone replacement. The real concern is indirect: Mounjaro slows gastric emptying (how quickly food leaves your stomach), which may theoretically affect absorption of oral medications, including some HRT formulations.
- If you take oral HRT (tablets), inform your prescriber before starting Mounjaro
- Transdermal HRT (patches) bypasses the stomach and is not affected by gastric slowing
- Your GP or prescriber may recommend timing HRT doses away from Mounjaro injections or monitoring hormone levels more closely
- Individual responses vary—some people experience minimal impact on medication absorption
Always disclose all medications, including HRT, when requesting a Mounjaro prescription through a UK clinical assessment.
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.
Managing HRT Safely While Using Mounjaro
If you're eligible for Mounjaro—including those with a BMI of 27–29.9 with weight-related health conditions—your prescriber can help you navigate HRT and tirzepatide together. Some women find that weight loss itself improves menopausal symptoms like hot flushes and night sweats, potentially reducing HRT dosing needs over time. However, this is individualised and must be managed by your GP or specialist. Keep a symptom diary while adjusting either treatment, and report any changes in how your HRT feels or any unusual side effects to your healthcare team. The MyWeightCheck GLP-1 weight loss calculator can help you estimate potential weight loss with Mounjaro, which may be useful context when discussing long-term health goals with your prescriber.
- 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 stop my HRT from working?
No, Mounjaro does not directly block HRT. However, Mounjaro slows stomach emptying, which may affect absorption of oral HRT tablets. Transdermal HRT (patches) is not affected. Your GP can advise whether your specific HRT formulation needs any adjustment or timing changes.
Should I tell my prescriber I take HRT before starting Mounjaro?
Yes, absolutely. Always disclose all medications, including HRT, during your clinical assessment for Mounjaro. This allows your prescriber to assess any potential interactions and monitor you appropriately.
Can I use Mounjaro with a patch-based HRT?
Transdermal HRT patches are unlikely to be affected by Mounjaro's effect on stomach emptying because patches bypass the digestive system entirely. This makes patches a potentially simpler option alongside Mounjaro, though your GP should confirm this for your specific situation.
Might weight loss from Mounjaro reduce my HRT needs?
Possibly. Some women find that weight loss improves menopausal symptoms, potentially reducing HRT dosing needs over time. However, any changes to HRT should only be made by your GP—never adjust doses yourself without medical guidance.
Is Mounjaro safe for perimenopausal or postmenopausal women?
Mounjaro is prescribed to adults of all ages who meet eligibility criteria. Perimenopausal and postmenopausal women can use Mounjaro, but your individual health profile (including HRT use and other medications) must be assessed during a clinical consultation. Your GP is best placed to advise whether it's suitable for you.
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.