Calcium Blood test

A calcium blood test is performed to measure two types of calcium:

• Total calcium: Calcium, that is both free and bound to circulating blood proteins, mainly albumin
• Ionised or free calcium: Calcium, which is not bound to circulating blood proteins and is in biologically active form

A physician will recommend a calcium blood test if you exhibit symptoms of

• Hypercalcaemia, such as fatigue, depression, mental confusion, anorexia, nausea, vomiting, constipation, increased urination, changes in an electrocardiogram and in some patients, cardiac arrhythmia.
• Hypocalcaemia, such as numbness and tingling sensations in the mouth area, fingers and toes; muscle cramps in the back and legs; swallowing difficulties; irritability; depression and personality changes; fatigue; seizures and other uncontrolled movements; or skin symptoms, such as chronic itching, excess hair fall and brittle nails.

Calcium blood tests are also recommended in case of symptoms of certain bone diseases; cancers of breast, lungs, kidneys, blood and neck; chronic kidney or liver disease; disorders of the parathyroid gland; excess thyroid hormone, either due to overactive thyroid gland or over supplementation of thyroid medicines; or abnormal vitamin D levels.

Special preparation is not required for solely a calcium blood test. However, the same blood sample may be used to test other parameters and may require you to fast, usually for eight hours. Inform your physician if you are taking any of the following drugs as they may cause an increase or decrease in your blood calcium levels and give misleading results: bicarbonates, bisphosphonates, lithium, vitamin A, cinacalcet, calcitonin, hydrochlorothiazide, furosemide, oestrogens or any steroids.

For this test, a blood sample is usually taken from a  vein of an elbow or wrist. The procedure lasts for less than 5 minutes.

A thin needle is inserted into the vein, which will cause a sharp pricking sensation for a few seconds, and a small amount of blood (usually 2-3 mL) is filled into a syringe or blood sample container.

Normal results: Here are the normal values for a calcium blood test:

• Ionised calcium: 1.1-1.35 mmol/L (4.64-5.28 mg/dL)
• Total calcium in adults: 8.5-10.3 mmol/L (8.9-10.1 mg/dL)

Abnormal results:

The following values of blood calcium may be obtained in case of Hypercalcaemia

• Mild hypercalcaemia
  • Total calcium:10.5-11.9 mg/dL (2.5-3 mmol/L) 
  • Ionised calcium: 5.6-8 mg/dL (1.4-2 mmol/L)
• Moderate hypercalcaemia
  • Total calcium: 12-13.9 mg/dL (3-3.5 mmol/L)
  • Ionised calcium: 8-10 mg/dL (2-2.5 mmol/L)
• Hypercalcaemia crisis
  • Total calcium: 14-16 mg/dL (3.5-4 mmol/L)
  • Ionized calcium:10-12 mg/dL (2.5-3 mmol/L)

Symptoms of hypercalcaemia can be seen even at mildly increased levels, but some patients could be asymptomatic. In moderate hypercalcaemia, calcium stone formation in kidneys, skin, vessels, lungs, heart and stomach can occur. Severe hypercalcaemia can be a medical emergency wherein coma and cardiac arrest can occur.

Before undertaking a diagnostic workup, it is essential to be sure that true hypercalcaemia, not a false-positive laboratory test, is present. A false-positive diagnosis of hypercalcaemia is usually the result of a disruption of albumin synthesis. Hypercalcaemia is a long-term problem, and it is cost-effective to obtain several serum calcium measurements to adequately treat it.

Hypocalcaemia

If the results of a calcium blood test are lower than normal, it may indicate hypoparathyroidism, deficiency of vitamin D, deficiency of magnesium, pancreatitis or kidney disease. Although almost one-half patients in intensive care units are reported to have calcium concentrations of less than 2.1 mmol/L (8.5 mg/dL), most do not have a reduced ionised calcium level. Care must be taken while interpreting low calcium levels, as it can be reflective of a variety of severe or acute illnesses. In a patient with hypocalcaemia, it is also necessary to measure albumin levels as it helps to distinguish between true hypocalcaemia and false hypocalcaemia.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is purely from an educational perspective and is in no way a substitute for medical advice from a qualified doctor.