Calcium
Calcium is the most abundant mineral in the body, with 99% stored in bones and teeth. The remaining 1% in blood is critical for nerve transmission, muscle contraction, blood clotting, and cell signaling. Serum calcium exists in three forms: protein-bound (40%, mainly to albumin), complexed (10%), and ionized/free (50%, biologically active).
Why it matters: Calcium is tightly regulated by PTH, vitamin D, and calcitonin. High calcium (hypercalcemia) is associated with kidney stones, bone pain, constipation, and confusion ("stones, bones, groans, and moans"). Low calcium (hypocalcemia) is associated with muscle cramps and tingling, and in severe cases more serious effects.
May increase with:
May decrease with:
What is Calcium?
Calcium is the most abundant mineral in the body, with 99% stored in bones and teeth. The remaining 1% in blood is critical for nerve transmission, muscle contraction, blood clotting, and cell signaling. Serum calcium exists in three forms: protein-bound (40%, mainly to albumin), complexed (10%), and ionized/free (50%, biologically active).
What might a high or low Calcium mean?
Calcium is tightly regulated by PTH, vitamin D, and calcitonin. High calcium (hypercalcemia) is associated with kidney stones, bone pain, constipation, and confusion ("stones, bones, groans, and moans"). Low calcium (hypocalcemia) is associated with muscle cramps and tingling, and in severe cases more serious effects.
What is the typical reference range for Calcium?
The general-population reference range shown here is 2.15 – 2.55 mmol/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.
What can affect Calcium?
It may be higher with: Primary hyperparathyroidism (parathyroid adenoma), Malignancy (bone metastases, PTHrP secretion), Vitamin D excess, Thiazide diuretics, Prolonged immobilization, Sarcoidosis, Lithium. It may be lower with: Vitamin D deficiency (most common cause), Hypoparathyroidism (post-surgical), Chronic kidney disease, Magnesium deficiency (impairs PTH secretion), Pancreatitis, Low albumin (total calcium low but ionized may be normal), Malabsorption.