Bones might be the first thing that comes to mind when you think of calcium, but calcium performs other tasks in the body besides building strong bones. Calcium also helps transmit nerve impulses and regulate muscle contractions. Approximately 99 percent of calcium is stored in the bones, with just 1 percent found in the blood, nerves, muscle and other tissues. Calcium in the blood exists in bound and unbound forms. The unbound form is called free or ionized calcium. Common blood tests include total and free calcium.
Total Calcium Ranges
Total calcium levels change as you age. For adults, the normal calcium range is approximately 8.5 to 10.5 mg/dL. In women older than 45, however, levels tend to increase slightly until around age 75, when they begin to gradually decrease. Different laboratories list different normal ranges, but they typically vary less than 0.5 mg/dL.
Free calcium is the only active form of calcium in the fluid outside your cells, which makes it the best indicator of calcium status in the body. Around half of total calcium is normally in the form of free calcium. Normal free calcium levels in an adult range from approximately 4.5 to 5.1 mg/dL. As with total calcium levels, normal ranges may vary from one laboratory to another. Talk with your doctor to determine if your free calcium levels are a concern.
- Advanced Human Nutrition; Denis Medeiros and Robert E.C. Wildman
- Fluids and Electrolytes Made Incredibly Easy; Springhouse
- Clinical Methods: The History, Physical, and Laboratory Examinations: H.Kenneth Walker, et al.
- Hypercalcemia Pathophysiology and Treatment; Franco Lumachi and Stefano M. M. Basso (eds.)
- Critical Care Medicine: The Essentials; John J. Marini and Arthur P. Wheeler
- Indian Journal of Clinical Biochemistry: Serum Calcium Measurement: Total Versus Free (ionized) Calcium