Serum Calcium Blood Test

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A serum calcium blood test is performed to measure a patient’s blood-calcium levels. Calcium is necessary for cell function. It helps keep teeth and bones strong. Calcium is also essential for helping with muscle contraction, blood clotting, heart function, and nerve signaling. This test may also be referred to as Ca++ or Ca+2.

Why this Test is Performed

If a doctor suspects parathyroid diseases, bone diseases, or kidney diseases, he or she may have the patient have this test done. This test may also be used to monitor such conditions.

Preparation and Procedure

Preparation may be necessary for some patients. Certain drugs may increase the level of calcium in the blood, therefore, may need to be temporarily discontinued before having this test. These may include calcium salts, thiazide diuretics, vitamin D, lithium, and thyroxine. Consuming more than two quarts or milk everyday may also increase blood-calcium levels.

The serum calcium blood test is done by drawing blood from a vein. This involves gently inserting a needle into one of the patient’s veins and then allowing the blood to collect into a vial. A tourniquet will be tied around the arm a few inches above the intended puncture site. The health care provider will feel for a vein and then gently insert the needle. Once enough blood is collected, the tourniquet is untied and removed, the needle is removed, and a small bandage is placed over the puncture site. Some slight bruising or soreness may occur after this is done.

Infants and young children will typically have their blood drawn using a lancet. The lancet will puncture the skin and then the blood will collect onto a test strip or slide, or into a pipette.

How the test feels will vary among patients. Patients have reported a slight prick to moderate pain. For most patients any discomfort experienced is tolerable.


8.5 to 10.2 mg/dL are the normal values range. If levels are higher than normal, it may indicate:

  • Addison’s disease
  • Excessive calcium intake
  • Hyperparathyroidism
  • Metastatic bone tumor
  • Multiple myeloma
  • Paget’s disease
  • Sarcoidosis
  • Using certain medications like tamoxifen, thiazides, and lithium
  • Excessive vitamin D level
  • Infections causing granulomas like certain mycobacterial infections and fungal infections, and tuberculosis
  • Milk-alkali syndrome
  • Overactive thyroid gland
  • Prolonged immobilization
  • Tumors that produce a substance that is parathyroid-like

If levels are lower than normal, it may indicate:

  • Hypoparathyroidism
  • Liver disease
  • Malabsorption
  • Pancreatitis
  • Vitamin D deficiency
  • Kidney failure
  • Magnesium deficiency
  • Osteomalacia
  • Rickets

Other conditions that may warrant this test may include:

  • Delirium
  • Multiple endocrine neoplasia II
  • Renal cell carcinoma
  • Dementia
  • Multiple endocrine neoplasia I
  • Secondary hyperparathyroidism


MedlinePlus. (2009). Calcium – Blood Test. Retrieved on November 21, 2010 from MedlinePlus:

Lab Tests Online. (2010). Calcium. Retrieved on November 21, 2010 from Lab Tests Online: