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
Mounjaro and Bone Density — What You Need to Know
gradual weight management from medications like Mounjaro (tirzepatide) can affect bone density, and this is an important consideration for NHS patients considering this prescription treatment. Bone density naturally decreases with weight loss, particularly when loss occurs quickly or over longer treatment periods. This guide explains what the evidence shows, what the NHS recommends, and how your GP can monitor your skeletal health during and after treatment with tirzepatide.
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.
How Weight Loss Affects Bone Density
Bone density tends to decline during significant weight loss because bones bear less load and the body remodels skeletal tissue more rapidly than normal. Research shows that weight loss of 5–10% of body weight can result in a measurable reduction in bone mineral density, particularly in the spine and hip. With Mounjaro dose titration reaching up to 15 mg weekly, average weight loss in clinical trials reached approximately 20% of body weight over 72 weeks — a rate that does increase the risk of bone density loss. The SURMOUNT trials demonstrated this effect, though bone fracture rates were not significantly elevated in the trial populations studied. However, the NHS recognises that rapid or substantial weight loss requires careful monitoring, particularly in older adults, postmenopausal women, and those with existing osteoporosis risk factors. Your GP can assess your individual bone health risk using standard screening tools like DEXA scans before starting tirzepatide and periodically during treatment.
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 Monitoring and Management Recommendations
If you're prescribed Mounjaro through NHS specialist tier 3 weight management services, your healthcare team should assess your baseline bone health risk before starting treatment. This includes reviewing your age, sex, family history, medications (particularly corticosteroids), and lifestyle factors like calcium intake and physical activity. The NHS recommends that patients taking GLP-1 or dual GIP/GLP-1 medications maintain adequate calcium and vitamin D intake throughout treatment — the NHS recommends 700 mg calcium daily for adults and 10 micrograms vitamin D daily. Regular weight-bearing and resistance exercise helps preserve bone density during weight loss. If you have existing osteoporosis, a history of fractures, or are postmenopausal, discuss bone monitoring with your GP before starting Mounjaro. Your prescriber may recommend a DEXA scan and repeat monitoring during longer-term treatment.
- 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 cause osteoporosis?
Mounjaro (tirzepatide) does not directly cause osteoporosis. However, the gradual weight management it enables can reduce bone density over time, particularly with significant loss (15–20% body weight). The SURMOUNT trials did not show elevated fracture rates, but NHS guidance recommends monitoring bone health in at-risk groups, including postmenopausal women and older adults. Your GP can assess your individual risk.
What does the NHS say about Mounjaro and bone health?
The NHS recognises that gradual weight management from medications like Mounjaro can affect bone density and recommends baseline bone health assessment before starting treatment, particularly in at-risk populations. NHS guidance emphasises maintaining adequate calcium (700 mg daily) and vitamin D (10 micrograms daily), plus regular weight-bearing exercise. Your tier 3 weight management service should discuss monitoring if you have existing bone health concerns.
Can I prevent bone density loss while taking Mounjaro?
Yes. The NHS recommends maintaining adequate calcium and vitamin D intake, engaging in regular weight-bearing and resistance exercise, avoiding smoking and excessive alcohol, and having a balanced diet. These measures support bone health during weight loss. If you have osteoporosis risk factors, your GP may recommend a DEXA scan before starting treatment and periodic monitoring during longer-term use of tirzepatide.
Who should have bone density checks before starting Mounjaro?
The NHS recommends bone health screening before Mounjaro treatment if you are postmenopausal, over 60, have a family history of osteoporosis, take corticosteroids, have previous fractures, or have other risk factors. Your GP or specialist team can assess whether a DEXA scan is appropriate for you based on your individual health profile.
Does Mounjaro affect bone density differently than Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) enable weight loss that can affect bone density in similar ways. The primary difference is that Mounjaro typically results in greater average weight loss (approximately 20% vs 15% body weight in trials), which may increase bone density monitoring importance. Your GP can advise which medication suits your individual health circumstances.
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.