Calcium blood test
Ca+2; Serum calcium; Ca++; Hyperparathyroidism - calcium level; Osteoporosis - calcium level; Hypercalcemia - calcium level; Hypocalcemia - calcium levelThe calcium blood test measures the level of calcium in the blood.
This article discusses the test to measure the total amount of calcium in your blood. About one half of the calcium in the blood is attached to proteins, mainly albumin.
A separate test that measures calcium that is not attached to proteins in your blood is sometimes performed. Such calcium is called free or ionized calcium.
Ionized calcium
Ionized calcium is calcium in your blood that is not attached to proteins. It is also called free calcium. All cells need calcium in order to work. ...
Read Article Now Book Mark ArticleCalcium can also be measured in the urine.
Urine
This test measures the amount of calcium in the urine. All cells need calcium in order to work. Calcium helps build strong bones and teeth. It is ...
Read Article Now Book Mark ArticleHow the Test is Performed
A blood sample is needed.
Blood sample
Venipuncture is the collection of blood from a vein. It is most often done for laboratory testing.
Read Article Now Book Mark ArticleHow to Prepare for the Test
Your health care provider may tell you to temporarily stop taking certain medicines that can affect the test. These medicines may include:
- Calcium salts (may be found in nutritional supplements or antacids)
- Lithium
- Thiazide diuretics (water pills)
- Levothyroxine
- Vitamin D
Drinking too much milk (2 or more quarts or 2 liters a day or a large amount of other dairy products) or taking too much vitamin D as a dietary supplement can also increase blood calcium levels.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
Why the Test is Performed
All cells need calcium in order to work. Calcium helps build strong bones and teeth. It is important for heart function, and helps with muscle contraction, nerve signaling, and blood clotting.
Your provider may order this test if you have signs or symptoms of:
- Certain bone diseases
- Certain cancers, such as multiple myeloma, or a cancer of the breast, lung, neck, and kidney
- Chronic kidney disease
Chronic kidney disease
Chronic kidney disease is the slow loss of kidney function over time. The main job of the kidneys is to remove wastes and excess water from the body...
Read Article Now Book Mark Article - Chronic liver disease
Chronic liver disease
Cirrhosis is scarring of the liver and poor liver function. It is the last stage of chronic liver disease.
Read Article Now Book Mark Article - Disorders of the parathyroid glands (hormone made by these glands controls calcium and vitamin D levels in the blood)
- Disorders that affect how your intestines absorb nutrients (intestinal malabsorption)
- High vitamin D blood level
- Overactive thyroid gland (hyperthyroidism) or taking too much thyroid hormone medicine
Your provider may also order this test if you have been on bed rest for a long time.
Normal Results
Normal values range from 8.5 to 10.2 mg/dL (0.47 to 0.57 millimol/L).
Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
A higher than normal level may be due to a number of health conditions. Common causes include:
- Being on bed rest for a long time.
- Consuming too much calcium or vitamin D.
- Hyperparathyroidism (parathyroid glands make too much of their hormone; sometimes associated with a low vitamin D level).
Hyperparathyroidism
Hyperparathyroidism is a condition in which 1 or more of the parathyroid glands in your neck produce too much parathyroid hormone (PTH).
Read Article Now Book Mark Article - Infections that cause granulomas such as tuberculosis and certain fungal and mycobacterial infections.
- Multiple myeloma, T cell lymphoma and certain other cancers.
Multiple myeloma
Multiple myeloma is a blood cancer that starts in the plasma cells in the bone marrow. Bone marrow is the soft, spongy tissue found inside most bone...
Read Article Now Book Mark Article - Metastatic bone tumor (bone cancer that has spread).
Metastatic bone tumor
A bone tumor is an abnormal growth of cells within a bone. A bone tumor may be cancerous (malignant) or noncancerous (benign).
Read Article Now Book Mark Article - Overactive thyroid gland (hyperthyroidism) or too much thyroid hormone replacement medicine.
- Paget disease. Abnormal bone destruction and regrowth, causing deformity of the affected bones.
Paget disease
Paget disease is a disorder that involves abnormal bone destruction and regrowth. This results in deformity of the affected bones.
Read Article Now Book Mark Article - Sarcoidosis. Lymph nodes, lungs, liver, eyes, skin, or other tissues become swollen or inflamed.
Sarcoidosis
Sarcoidosis is a disease in which inflammation occurs in the lymph nodes, lungs, liver, eyes, skin, and/or other tissues.
Read Article Now Book Mark Article - Tumors producing a parathyroid hormone-like substance.
- Use of certain medicines such as lithium, tamoxifen, and thiazides.
A lower than normal levels may be due to:
- Disorders that affect absorption of nutrients from the intestines (intestinal malabsorption)
- Hypoparathyroidism (parathyroid glands do not make enough of their hormone)
Hypoparathyroidism
Hypoparathyroidism is a disorder in which the parathyroid glands in the neck do not produce enough parathyroid hormone (PTH).
Read Article Now Book Mark Article - Kidney insufficiency or failure
- Low blood level of albumin
- Liver disease
- Magnesium deficiency
- Pancreatitis
- Vitamin D deficiency
Risks
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
- Multiple punctures to locate veins
References
Chonchol M, Smogorzewski MJ, Stubbs JR, Yu ASL. Disorders of calcium, magnesium, and phosphate balance. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 18.
Klemm KM, Klein MJ, Zhang Y. Biochemical markers of bone metabolism. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 16.
Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
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Review Date: 11/19/2023
Reviewed By: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.