Which laboratory pattern is typical of hypocalcemia?

• A. Low ionized calcium and low total calcium
• B. High calcium and high phosphate
• C. High magnesium and high calcium
• D. Low potassium and normal calcium

Answer: (A)

Calcium homeostasis is best assessed by the physiologically active portion, ionized calcium. While total calcium can be misleading because it depends on albumin binding, true hypocalcemia is reflected by a low ionized calcium. When both ionized calcium and total calcium are reduced, it indicates genuine hypocalcemia rather than a situation where total calcium is low only because albumin is low.

Other patterns don’t fit hypocalcemia as well. A high calcium (with or without high phosphate) would point away from hypocalcemia. A pattern with high magnesium and high calcium isn’t typical for low calcium states. Low potassium with normal calcium doesn’t describe low calcium.