Blood test

Normal calcium level in the blood

Blood test
Normal calcium level in the blood
Last update: 05/03/2020

What is the normal level of calcium in the blood?

Adults: 8.5-10.9 mg/dL
Children: 8.5-10.9 mg/dL

In the International System of Units (SI), calcium in the blood is measured in mmol/l. The normal blood calcium levels in the SI are:

Adults: 2.12-2.72 mmol/L
Children: 2.12-2.72 mmol/L

Why normal levels can differ across different labs?

Each laboratory must establish its own normal ranges for calcium in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels, according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.

Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.

What is the role of calcium?

Calcium is an essential element to perform specialized functions in all the cells of our body. That is the reason why calcium in the blood (Ca2+) must be carefully controlled and it is so important to maintain calcium blood levels within a fairly narrow range.

Calcium is one of the most important and the most abundant mineral in the human body. Calcium is essential for a good function of our organism. It is essential to develop and maintain healthy bones and teeth. Calcium phosphate salts forming crystals constitute the main component of bones and teeth. Calcium plays also an important role in the activity of the heart (cardiac muscle contraction) and along with potassium and sodium is necessary to the transmission of nerve impulses to the muscle.

Calcium is supplied in the food we eat and it is excreted by the kidneys. Bones are the main storage place of calcium in the body (99%). However, it is possible to find some calcium in the blood.

Blood calcium can be free or bound to other substances. 40% of blood calcium is free and is called ionized calcium or free calcium. 50% is bound to proteins (albumin mainly) and 10% is bound to other minerals (phosphorus, etc.)

Blood calcium concentration is regulated by:

  • Parathyroid hormone (PTH): PTH Increases intestinal calcium absorption and enhances the release of calcium from the reservoir contained in the bones. Parathyroid hormone is secreted from the parathyroid glands.
  • Calcitonin. Calcitonin inhibits intestinal calcium absorption and has an inhibitory effect of bone resorption. Calcitonin is produced by the parafollicular cells of the thyroid gland.

Vitamin D, lactose or acid blood pH can increase calcium absorption from the intestine.

What is a calcium blood test for?

The calcium blood test does not measure levels of bone calcium, but rather how much calcium is circulating in the blood.

The calcium blood test is ordered to find:

  • If the kidneys are working properly
  • Functional state of the parathyroid glands
  • Calcium metabolism
  • Bone diseases

High calcium blood levels (hypercalcemia or hypercalcemia) can be a result of suffering from hyperparathyroidism or bone mass loss.

When the calcium blood level is low, it can be a sign of hypoparathyroidism, kidney failure, vitamin D deficiency, pancreatitis or rickets.

Where can I find more information about calcium in the blood?

You can visit our pages about:

Which values are considered a normal calcium level in the blood?

The following values are considered to be normal values:

IMPORTANT: These levels are expressed in mg/dl. They are an example of a healthy man of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

8.5 mg/dL8.6 mg/dL8.7 mg/dL8.8 mg/dL8.9 mg/dL9 mg/dL9.1 mg/dL9.2 mg/dL
9.3 mg/dL9.4 mg/dL9.5 mg/dL9.6 mg/dL9.7 mg/dL9.8 mg/dL9.9 mg/dL10 mg/dL
10.1 mg/dL10.2 mg/dL10.3 mg/dL10.4 mg/dL10.5 mg/dL10.6 mg/dL10.7 mg/dL10.8 mg/dL
10.9 mg/dL       
Medically reviewed by Javier Muga Bustamante Ph.D. on 05/03/2020


  • Concise Book of Medical Laboratory Technology: Methods and Interpretations. 2nd Edition. 2015. Ramnik Sood. ISBN: 978-93-5152-333-8. Pag. 493.
  • Tietz. Fundamentals of Clinical Chemistry. Carl A. Burtis, Edward R. Ashwood, David E. Bruns, Barbara G. Sawyer. WB Saunders Company, 2008. Pag 712. ISBN: 978-0-7216-3865-2.
  • Common Terminology Criteria for Adverse Events (CTCAE). Version 5.0.Published: November 27, 2017. U.S. Department of health and human Services. Available on:
  • Thomas L, ed. Clinical Laboratory Diagnostics Use and Assessment of Clinical Laboratory Results, 1st ed. Frankfurt/Main: TH-Books Verlagsgesellschaft, 1998:231-241.

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