How to recognize secondary causes of bone fragility in relation with an abnormal calcium and phosphate laboratory in general practice ? Through clinical cases presentations we will discuss the calcium and phosphate abnormalities which can be related to bone fragility and for which a-specific approach must be proposed. It can be abnormal results of calcium, phosphate or vitamin D. Some causes are frequent, others are iatrogenic, and others are related to a rare disease sometimes of genetic cause which consequences are more important than expected.