Frailty is a geriatric syndrome that has been characterized by an increased vulnerability against external stressors. The aim of laboratory investigations in the context of frailty is to screen for conditions that are pathophysiologically related to the development of this syndrome. Successful therapy of these conditions may help to stabilize the elderly individual who is at risk for functional decline and increasing frailty. In this review laboratory parameters for the detection of anemia, impaired vitamin D intake, thyroid and gonadal function are described in their relationship with developing frailty.