Several widely used medications can cause bone loss, including the antacids Prilosec and Prevacid, blood-sugar-lowering drugs Actos and Avandia, anti-seizure meds Dilantin or phenobarbital, and antidepressants such as Prozac, Zoloft, and Lexapro. "These medications drain magnesium stores, because magnesium is needed to break down and neutralize the drug chemicals in the liver," Dean says. Many drugs also alter hinder calcium absorption.

But the medications that are hardest on bones are corticosteroids such as prednisone and cortisone, according to Recker. He says people who use them frequently for skin problems, arthritis, or other inflammatory conditions tend to have significantly weakened bones. If you're on any prescription med, there's probably a good reason, and you won't likely ditch the drug for your bones' sake. Nor should you, says Recker, but then you'll "just have to work harder to prevent bone loss." Since the risk of bone loss increases with higher doses of corticosteroids, Recker says to make sure you're only taking as much as you need. If taking high doses of prednisone and cortisone, Recker suggests his patients take an osteoporosis medication right along with it to counteract the corticosteroid's effect.