Dual-energy X-ray Absorptiometry or DXA measures Bone Mineral Density or BMD. Tests on DXA machines are commonly called bone density scans. These machines became available over 20 years ago. The on board computer gives a simple number for a reading. It looked like a very simple and accurate way to test for Osteoporosis. We now know that it is neither.
Your Total daily intake of Calcium should be 1200 to 1500 mg. That is 4 to 5 – 8 oz glasses of milk every day. Or you can have other sources of Calcium in your Diet. If you do not get 1200 to 1500 mg of Total Calcium in your Diet, you should take Calcium Supplements.
In 2010 the “Optimal” level most often quoted at National Osteoporosis Foundation and at American Society for Bone Mineral Research was 32 to 100ng/ml. This is markedly different from the original “normal” range of 15 to 40ng/ml.