DEXA (which stands for dual energy x-ray absorptiometry) scanning uses special x-rays to measure the density of your bones. The density of your bones will show how strong they are. The exposure to x-rays is very low and is similar to what you would receive on a long distance plane flight.
What to expect
You will lie very still on a padded table for 5-10 minutes while the arm of the machine passes over the area to be measured (usually the lower spine and hip, although the forearm can also be measured). This is quite painless.
You can remain in your normal clothing, although you may have to take off anything with large buttons, buckles or metal zips.
Read more about DEXA Bone Densitometry here.