The FRAX score is an online calculator that estimates your chance of breaking a bone from osteoporosis over the next 10 years. It combines age, sex, body size and a set of clinical risk factors, with or without a bone density result, to give two numbers: the 10-year probability of a hip fracture and of a major osteoporotic fracture. In osteoporosis risk assessment, doctors use these figures alongside a DEXA scan to decide who benefits from treatment.
Bone density alone misses many people who go on to fracture, because fracture risk depends on more than how dense the bone is. FRAX was designed to fill that gap. In this article I explain how it works, how to read the results and where its limits lie.
What Is the FRAX Score?
FRAX stands for Fracture Risk Assessment Tool. It was developed at the University of Sheffield and released in 2008, and it is now built into many national osteoporosis guidelines. The calculator uses country-specific models, because fracture and death rates vary between populations.
It reports two results:
- Major osteoporotic fracture (MOF) probability: the 10-year chance of a clinical spine, hip, forearm or upper arm (humerus) fracture.
- Hip fracture probability: the 10-year chance of a hip fracture specifically.
FRAX is designed for adults aged 40 to 90 who have not already been treated for osteoporosis.
What FRAX Measures: The Risk Factors
Each input reflects a factor known to raise fracture risk independently of bone density.
| FRAX input | Why it matters |
|---|---|
| Age | Risk rises steeply with age, beyond what bone density explains |
| Sex | Women lose bone faster after menopause |
| Weight and height (BMI) | Low body weight is linked to lower bone mass and higher risk |
| Previous fragility fracture | One of the strongest predictors of future fractures |
| Parent fractured hip | Reflects inherited bone strength and structure |
| Current smoking | Impairs bone formation |
| Glucocorticoid use | Oral steroids for 3 months or more at 5 mg prednisolone daily or equivalent weaken bone |
| Rheumatoid arthritis | Inflammation and treatment both affect bone |
| Secondary osteoporosis | Conditions such as type 1 diabetes, untreated hyperthyroidism, early menopause or malabsorption |
| Alcohol, 3 or more units daily | Affects bone and increases fall risk |
| Femoral neck BMD (optional) | Adds bone density to refine the estimate |
These factors connect directly to the pathophysiology of osteoporosis, in which bone breakdown by osteoclasts outpaces bone formation by osteoblasts. Hormonal change, especially falling estrogen after menopause, is a central driver, while genetics shapes the peak bone mass a person reaches in early adulthood.
FRAX and DEXA: How They Work Together
A DEXA scan (dual-energy X-ray absorptiometry) measures bone mineral density and reports a T-score, which compares your bone density with that of a healthy young adult.
- Normal: T-score of −1.0 or above
- Osteopenia (low bone mass): between −1.0 and −2.5
- Osteoporosis: −2.5 or below
The T-score defines osteoporosis, but most fractures actually occur in people in the osteopenia range, simply because far more people fall into it. FRAX is most useful here: it helps decide which people with low bone mass have enough overall risk to justify medication.
FRAX can also be run without a bone density result. This is useful in areas where DEXA is limited, and to decide who should be referred for a scan.
Interpreting Your FRAX Results
Treatment thresholds vary by country. In the United States, guidance from the Bone Health and Osteoporosis Foundation recommends considering treatment in people with osteopenia when:
- the 10-year hip fracture probability is 3% or higher, or
- the 10-year major osteoporotic fracture probability is 20% or higher.
Treatment is also generally recommended regardless of FRAX for anyone with a T-score of −2.5 or below, or a prior hip or vertebral fragility fracture. In the United Kingdom, the National Osteoporosis Guideline Group uses age-dependent thresholds, so the level that triggers treatment rises with age.
In my practice, I treat the FRAX number as the start of a conversation rather than a verdict. A result just below a threshold in someone with recent falls may still warrant treatment.
Limitations of FRAX
FRAX is powerful but simplified. It answers most risk factors with a yes or no, so it cannot capture everything.
- Dose and number: it does not account for high-dose steroid use or for multiple prior fractures, both of which raise risk further.
- Recent fracture: risk is especially high in the first couple of years after a fracture, which FRAX does not reflect.
- Falls: fall history is not an input, although falls cause most fractures.
- Spine density: only femoral neck BMD is used, so a much lower spine value can be missed.
- Other conditions: type 2 diabetes, for example, raises fracture risk in ways FRAX underestimates.
Clinicians can adjust for some of these. The trabecular bone score (TBS), derived from spine DEXA images, assesses bone microarchitecture and can refine the estimate, and newer versions of the tool allow adjustments for factors such as steroid dose and recent fracture.
From Risk Score to Treatment
Once FRAX and DEXA identify high risk, the next step is treatment. Treating osteoporosis usually combines medication with lifestyle measures.
- Bisphosphonates such as alendronate, risedronate and zoledronic acid slow bone breakdown and are usually first-line.
- Denosumab, a monoclonal antibody given by injection, also reduces bone resorption.
- Anabolic agents such as teriparatide and romosozumab build new bone and are reserved for very high risk.
- Selective estrogen receptor modulators such as raloxifene are options for some postmenopausal women.
Foundations still matter: adequate calcium and vitamin D, weight-bearing and muscle-strengthening exercise, stopping smoking, limiting alcohol and preventing falls. Our article on the role of supplements in the management of osteoporosis covers calcium and vitamin D in more detail, and our osteoporosis guide brings the topic together.
Frequently Asked Questions
Can I calculate my own FRAX score?
Yes, the FRAX calculator is freely available online and anyone can enter their details. However, results are best interpreted with a doctor, who can account for factors the tool leaves out and decide whether a bone density scan or treatment is needed.
What is a high FRAX score?
In the United States, a 10-year hip fracture probability of 3% or more, or a major osteoporotic fracture probability of 20% or more, is generally considered high enough to discuss treatment. Other countries use different, often age-based, thresholds.
Can FRAX be used if I am already on osteoporosis treatment?
FRAX was designed for people who are not on treatment, so it may overestimate risk in those already taking medication. Doctors usually rely on bone density trends, new fractures and clinical judgment to monitor treated patients.
Does FRAX apply to men?
Yes. FRAX includes sex as an input and is validated for both men and women. Men generally have a lower fracture risk at the same age, which the calculator reflects.
