Le calcium and the mineral most common in the blood and it is also one of the most important. It is necessary for the proper functioning of all the cells of the body: it helps build strong bones and teeth, it is involved in cardiac function, muscle contraction, nerve signaling and blood coagulation.

Almost all of the calcium in the body is stored in the bones. In the blood, its quantity is strictly regulated: if the mineral is decreasing (we speak ofhypocalcemia), the bones release it into the bloodstream to restore balance. On the contrary, if the level is too high (we speak ofhypercalcemia), the calcium supplement is stored in the bones or excreted in the urine or stool.

The level of calcium in the body is determined by:

• food (dairy products, eggs, green vegetables, fruits, etc.)

• absorption of calcium from the intestines (a process in which vitamin D is involved)

• or the activity of the parathyroid glands, which are involved in the regulation of the blood calcium level

The doctor prescribes a dosage of calcium if he suspects, for example:

• a problem of parathyroid glands

• bone disease

• certain cancers

• or kidney or liver disease

The examination consists of a sample of venous blood, generally at the level of the elbow crease. The doctor may ask you to stop taking certain drugs that may interfere with the results of the test, such as calcium salts that can be found in food supplements or antacids, lithium or vitamin D.

It is possible to measure the total calcium level, about half of the calcium in the body being attached to transport proteins, in particular albumin, or free calcium (also called ionized calcium).

Note that calcium can also be quantified in urine.

The level of calcium in the blood is normally between 8,8 and 10,4 mg / dl (milligrams per deciliter). The level of ionized calcium (free) in the blood is normally between 4,6 and 5,3 mg / dl.

Note that the so-called normal values ​​of calcium in the blood may vary depending on the laboratories performing the analyzes.

High blood calcium levels may be a sign of:

• an hyperparathyroïdie : abnormally high production of parathyroid hormones by large parathyroids, resulting in increased blood calcium levels 

• of a cancer

• tuberculosis

• Paget’s disease, in which the bones grow too fast

• or simply the fact of lying down for too long

On the contrary, a low calcium level can reflect:

• low blood levels of albumin, a transport protein

• hypoparathyroidism: abnormally low production of parathyroid hormones by large parathyroids, resulting in low blood calcium levels 

• a high level of phosphate in the blood, caused by kidney damage for example (when the calcium level is low, the phosphate level is high and vice versa)

• malnutrition or alcoholism

• or to osteomalacia (bone decalcification)

Note that in children in full bone growth, the level of calcium is higher.