Calcium(Ca) Determination Reagent is an in vitro diagnostic quantitative test kit. Calcium is an essential mineral that serves many roles in the body, including bone formation, muscle movement, nerve signaling, and heart rhythm regulation. A calcium blood test may be ordered as part of a routine checkup or to screen for or monitor medical conditions affecting the bones, kidneys, or parathyroid gland (a set of tiny organs in the neck, right next to the thyroid gland).