Calcium

Level of ionized calcium is regulated by parathyroid hormone and vitamin D. Serum calcium equals the sum of ionized calcium plus complexed calcium and calcium bound to proteins (mostly albumin).

 Normal Range: 8.5-10.5 mg/dL

increased in: Hyperparathyroidism, malignancies secreting PTH-like substances (especially squamous cell carcinoma of lung, renal cell carcinoma), vitamin D excess, milk-alkali syndrome, multiple myeloma, Paget's disease of bone with immobilization, sarcoidosis, other granulomatous disorders, familial hypocalciuria, vitamin A intoxication, thyrotoxicosis, Addison's disease. Drugs: antacids (some), calcium salts, chronic diuretic use (eg, thiazides), lithium, others. 

 

Decreased in: Hypoparathyroidism, vitamin D deficiency, renal insufficiency, pseudohypoparathyroidism, magnesium deficiency, hyperphosphatemia, massive transfusion, hypoalbuminemia. 

 

Additional: Need to know serum albumin to interpret calcium level. For every decrease in albumin by 1 mg/dL, calcium should be corrected upward by 0.8 mg/dL.