The strength of bones is measured by their mass or thickness. Greater mass or high bone density means the bones are less likely to fracture. Bone mineral density (BMD) can be measured two ways. The first and easiest is done on the heel or finger. This is probably the type of test you and your friend had done.

The second is by X-rays called dual energy X-ray absorptiometry or DEXA. Either test gives a T-score to describe the thickness of the bone (BMD). Normal is a T-score above -1.0. Low bone density starts with a T-score between -1.0 and -2.5.

A T-score below -2.5 indicates osteoporosis or weak bones. You and your friend are both in the "normal" range. Your score is slightly better than your friend's. The scores are only for the bone tested. Different bones can have different densities. A normal score in one bone doesn't mean all other bones are the same.