Calcium

Calcium plays an important role in the body. It is involved in metabolic reactions, the regulation of the functioning of the heart, muscle cells, and nerve cells, and the development of bones and the normal coagulation of blood.

In blood, calcium exists in two forms. Ionised calcium circulates freely in the bloodstream. Only this free part of calcium takes part in the different metabolic reactions in the body. Some of the calcium is bound to proteins circulating in the bloodstream. This is a kind of “storage form” from which calcium can become ionised calcium and vice versa.

99 per cent of the calcium in the body is in the bones, where it functions as a strong mineral. It gives strength to bones and teeth. An adult’s bones contain approximately one kilogramme of calcium. Because some of the calcium in the bones changes when bones renew, an adult needs calcium in their diet every day. The body regulates the calcium concentration of the body and makes sure that calcium is always found where it is needed.

We get calcium from food, including dairy products, nuts, dark-green vegetables, tofu, juice, fish, oranges, and broccoli. Calcium is also added to food products.

Vitamin D is needed for nutritional calcium to be absorbed in the intestines. The level of calcium in the bloodstream is regulated by a parathyroid hormone secreted by the parathyroid gland, parathormone (fP-PTH). This parathyroid hormone regulates the secretion of calcium in urine and calcium metabolism in bones. If the level of calcium in the blood decreases, more parathyroid hormone is secreted in the bloodstream, which results in increased release of calcium from the bone to the bloodstream. Correspondingly, if there is excessive calcium in the bloodstream, the secretion of parathyroid hormone decreases, and calcium passes from blood to bone and is excreted in urine.

When should calcium levels be measured?

It is a good idea to have calcium tested (S-Ca, P-Ca, fS-Ca-Ion) when suffering from general symptoms, such as headache, loss of appetite, cramps, constipation, or fatigue. These can be a sign of too low a calcium concentration in the blood.

Too low calcium blood levels can cause nervous symptoms, such as muscle cramps, stinging and numbness in the arms and legs, and arrhythmia.

Calcium levels should also be checked if you suspect:

• Parathyroid disease
• Vitamin D deficiency
• Skeletal diseases
• Absorption disorders
• Kidney stone disease
• Kidney failure

What does a calcium test measure?

Total calcium (S-Ca) concentration includes both free calcium and calcium bound to proteins. If the calcium balance is to be examined in more detail, for example the concentration of albumin-corrected calcium (S-Ca-Albk) should be tested.