(A score less than -2.5 is considered osteoporosis, while your score of -3.4 is considered severe osteoporosis.) The Z-score compares you against an average person of your age and sex.

So, an elderly woman might have a low T-score of -2.6 and a Z-score of 0, meaning that she has the expected bone loss of a woman of her age and still has osteoporosis.