Z-scores compare you to a woman your age. T-Scores compare you to a woman between 25-30 years of age, at what is usually peak BMD. It used to be specifically a white woman, and I don't know if that is the case anymore. Doctors only use T-scores in diagnosing Osteoporosis. The good thing about oral Fosamax is, if you experience side effects, you can stop. I had horrible heartburn but had GERD to begin with, (with an upper esophageal sphincter that has been described as "flapping in the breeze") so it was not unexpected. I quit after the first dose, and still had some mild improvement and stabilization in my T-Scores 2 years later.