DEXA (DXA, dual-energy X-ray absorptiometry) is a technology that scans the body with X-rays of two energies. From how the tissues absorb these rays, the machine separately assesses bone mineral, fat and "lean" mass.
So DEXA has two uses: it is the "gold standard" of densitometry (diagnosing osteoporosis) and one of the most accurate methods of assessing body composition.
How it works
The machine sends X-rays of two different energies. Bone and soft tissue absorb them differently, and from the difference in absorption the software separately calculates bone mineral mass, fat and lean tissue.
The radiation dose is very small — less than an ordinary chest X-ray. The scan is done lying down and takes a few minutes.
DEXA for bones and for body composition
In bone mode DEXA measures mineral density (BMD) and gives the T- and Z-scores — the diagnosis of osteoporosis is built on this (see densitometry).
In body-composition mode DEXA assesses total and regional fat, lean and skeletal muscle mass, as well as visceral fat. For the accuracy of body fat percentage the method surpasses BMI and skinfold measurement and serves as a reference, including for assessing sarcopenia.
DEXA and densitometry — don't confuse them
Densitometry is the measurement of bone density (the task). DEXA is the technology that usually performs it, but it can do more: the same method also analyzes body composition. Put simply, every DXA densitometry is DEXA, but not every use of DEXA is limited to bones.
Calculate using this marker
Calculators where DEXA (Dual-energy X-ray absorptiometry) is used directly:
Frequently asked questions
Are DEXA and densitometry the same thing?
Not quite. Densitometry is the measurement of bone density; DEXA is the technology (dual-energy X-ray absorptiometry) that usually performs it. But DEXA is broader: the same method also measures body composition — fat, muscle, visceral fat.
How accurate is DEXA for body composition?
DEXA is one of the reference methods: it separately assesses fat, lean and bone mass and is noticeably more accurate than BMI or skinfold measurement. The result depends on the machine, so for tracking the trend it is better to be scanned on the same device.