Ionized Calcium Blood Test Guide

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Ionized calcium is a type of calcium not attached to proteins that flow freely through the blood. Calcium is something all cells require to function, and it is also essential for strong teeth and bones, for muscle contraction, blood clotting, heart function, and nerve signaling. An ionized calcium blood test is done to determine how much ionized calcium the patient has in his or her blood.

Why is this Test Done?

An ionized calcium blood test may be performed for a number of reasons. Parathyroid disease or kidney disease are two of the primary reasons a patient may need to undergo this blood test. If a doctor suspects certain neurologic disorders, high or low calcium levels, thyroid disease, cancer, intestinal disease, or malnutrition this test may be done. Other reasons include a critically ill patient being administered intravenous fluids or blood transfusions, patients with low albumin and other low-protein abnormalities, and patients undergoing major surgery.

If a patient has high ionized calcium levels, they may experience fatigue, appetite loss, constipation, needing to urinate frequently, weakness, vomiting, abdominal pain, increased thirst, and vomiting.

If a patient has low ionized calcium levels, they may experience abdominal cramping, tingling fingers, and muscle cramping.

Preparation and Procedure

This test requires a blood sample that is most often drawn from the patient’s wrist. The sample may also be taken, however, from the groin, inside of elbow, or another artery. A doctor will locate an artery and will look to ensure the hand is receiving blood from the ulnar and radial arteries. The puncture site is then cleaned with an antiseptic and the doctor inserts the needle. Once the sample is obtained and the needle is removed, the patient will be shown and told to apply firm pressure to the puncture site. This pressure is necessary to stop the bleeding and typically needs to be applied for about ten minutes. The patient will be monitored to ensure the bleeding does stop.

To prepare for this blood test the patient must abstain from drinking or eating anything six hours prior to this laboratory test. Certain medications may also have to be stopped temporarily as well. Such medications may include hydralazine, thiazide diuretics, calcium salts, lithium, and thyroxine. Only stop taking a medication with doctor’s permission.


Normal results essentially mean that the patient has a normal level of ionized calcium in their blood. If their ionized calcium levels are too high, they may be suffering from:

  • Hyperparathyroidism
  • Idiopathic hypocalciuria
  • Milk-alkali syndrome
  • Paget’s disease
  • Too much vitamin D
  • Using thiazide diuretics
  • Immobilization
  • Metastatic bone tumor
  • Multiple myeloma
  • Sarcoidosis
  • Certain type of tumors

If a patient’s ionized calcium levels are too low, they may be suffering from:

  • Hypoparathyroidism
  • Osteomalacia
  • Renal failure
  • Vitamin D deficiency
  • Malabsorption
  • Pancreatitis
  • Rickets


Lab Tests Online. (2010). Calcium. Retrieved on November 15, 2010 from Lab Tests Online:

MedlinePlus. (2010). Calcium – Ionized. Retrieved on November 15, 2010 from MedlinePlus: