What Is Calcium in a Blood Test?

Calcium is the most abundant mineral in your body. 99% is stored in bones; the remaining 1% in blood is critical for nerve signaling, muscle contraction, and clotting.

Normal Range

• Total calcium: 8.5–10.5 mg/dL
• Ionized calcium: 4.65–5.28 mg/dL (active form)
• Hypercalcemia: above 10.5
• Hypocalcemia: below 8.5

High Calcium Causes

• Primary hyperparathyroidism — most common in outpatients
• Cancer — most common in hospital
• Vitamin D toxicity
• Sarcoidosis
• Thiazide diuretics

Low Calcium Causes

• Vitamin D deficiency
• Hypoparathyroidism
• Chronic kidney disease
• Hypomagnesemia
• Pancreatitis

Symptoms

• High: fatigue, confusion, constipation, kidney stones
• Low: muscle spasms, tetany, numbness/tingling, seizures