Bone Density Scan (DEXA Scan)

Introduction

A bone density scan, also known as a DEXA scan, is a medical test used to measure the strength and density of a person’s bones. DEXA stands for Dual-Energy X-ray Absorptiometry, a specialized type of low-dose X-ray technology. The test helps determine whether a person has normal bone density, low bone density (osteopenia), or osteoporosis. Although people often refer to a DEXA scan as a “bone scan,” it is different from the nuclear medicine bone scan used to identify fractures, infections, or tumors. A DEXA scan specifically measures bone density and fracture risk.

Equipment Used in a Bone Density Scan

The equipment used for a DEXA scan is relatively simple. The patient lies comfortably on a padded examination table while a scanning arm passes slowly over the body. The machine uses two very low-energy X-ray beams to measure how much mineral, primarily calcium, is present within the bones. The amount of radiation exposure is very small—typically much lower than that of a standard chest X-ray. The test is painless, non-invasive, and usually takes only 10 to 20 minutes to complete.

Indications for a DEXA Scan

Doctors commonly order a DEXA scan when they are concerned that a patient may have osteoporosis or be at increased risk of fractures. Common reasons for ordering the test include women over age 65, men over age 70, individuals who have suffered a low-energy fracture, patients taking long-term corticosteroid medications, and people with medical conditions known to weaken bone. A DEXA scan may also be ordered when a patient has a strong family history of osteoporosis, significant weight loss, smoking history, or other risk factors for reduced bone strength.

Anatomical Areas that are Commonly Tested

The areas most commonly tested during a DEXA scan are the hip and the lumbar spine (lower back). These locations are chosen because they are common sites of osteoporotic fractures and provide a reliable estimate of overall bone health. In some situations, the forearm may also be scanned, particularly if the hip or spine cannot be measured accurately. Measuring these specific areas helps doctors estimate a patient’s future fracture risk and determine whether treatment may be needed to improve bone strength.

Understanding DEXA Scan Results

The results of a DEXA (bone density) scan are usually reported using T-scores and Z-scores. A T-score compares your bone density to that of a healthy young adult of the same sex and is the primary measurement used to diagnose osteopenia and osteoporosis. A Z-score compares your bone density to that of other people of the same age and sex and can help doctors determine whether factors other than normal aging may be contributing to bone loss.

Score Type	Result	Interpretation
T-Score	-1.0 or higher	Normal bone density
T-Score	Between -1.0 and -2.5	Osteopenia (bone density is lower than normal but not low enough to be considered osteoporosis)
T-Score	-2.5 or lower	Osteoporosis
Z-Score	Compared to people of the same age and sex	Helps determine whether bone density is lower than expected for age and whether additional factors may be contributing to bone loss

In general, the lower the T-score, the weaker the bones and the greater the risk of fracture. Doctors use these results, along with a patient’s age, medical history, and other risk factors, to determine whether treatment or additional evaluation is needed.

Other Types of “Bone Scans”

Although the term “bone scan” is often used to describe a DEXA scan, there are other imaging tests that evaluate bone health. A nuclear medicine bone scan uses a small amount of radioactive tracer to identify areas of increased bone activity, such as fractures, infections, arthritis, or cancer. Quantitative CT (QCT) scans can also measure bone density using computed tomography technology. In addition, some screening programs use heel ultrasound to estimate bone density, although this is generally less precise than a DEXA scan. Among these tests, DEXA remains the most widely used and most validated method for diagnosing osteoporosis.

Summary

A bone density scan, also called a DEXA scan, is a quick and painless test that measures how strong your bones are. It is commonly used to look for osteoporosis, a condition that makes bones weaker and more likely to break. The scan usually measures the hip and lower back and uses very low-dose X-rays. The results help doctors determine whether your bone density is normal, low (osteopenia), or in the osteoporosis range. By identifying weak bones early, a DEXA scan can help patients and their doctors take steps to reduce the risk of future fractures.

Edited by Stephen Pinney MD, June 8th, 2026.