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.
How to interpret the calcium test result?
Normally, the result is:
Reference values: 2.15–2.51 mmol/l
Read more about defining reference values.
Please contact your physician or other healthcare professional if you suspect an illness or need help interpreting the results.
What can cause elevated calcium values?
An increased calcium level in the blood is called hypercalcaemia. The reason is usually overactive parathyroid glands, which causes too much calcium to transfer from the bones to the blood. In the longer term, this can cause osteoporosis. Another reason for excessive calcium being resorbed from the bones to the blood is cancer that has spread to the skeletal system.
Excessive intake of vitamin D is a rarer cause of elevated calcium levels. In this case, the calcium received from food is absorbed too effectively. However, vitamin D needs to be consumed in excess of the necessary amount for a long time for the level of calcium to exceed the reference range.
Considerably elevated calcium levels are treated at hospital using fluid therapy and medicines. Overproduction of calcium caused by the parathyroid hormone is treated surgically by removing the enlarged parathyroid gland.
What can cause decreased albumin-corrected calcium values?
A decreased calcium level in the blood is known as hypocalcaemia. It is a rarer condition than excessive blood calcium levels.
Hypocalcaemia can be caused by the following reasons:
- Kidney failure
- Vitamin D deficiency (for example, vitamin D is not absorbed in the small intestine because of coeliac disease or insufficient intake of vitamin D)
- Hypoparathyroidism (underactive parathyroid)
- Nutrient absorption disorders
The most typical additional calcium tests:
- Parathormone regulates calcium balance (4560 fP-PTH)
- Vitamin D deficiency is a problem for many Finns (1220 D-25)
- After calcium test albumin-corrected calcium (6032 S-Ca-Albk)
- Phosphate (1432 fS-Pi)
- Magnesium (2303 S-Mg)
SYNLAB tests: Calcium, Arto Katajamäki https://www.yml.fi/tuotekuvaus_show.php?tuotenro=209
SYNLAB test list: Calcium, ionised (2019 fS-Ca-Ion) https://www2.synlab.fi/laboratoriokasikirja/tutkimuskuvaukset/kalsium/
Terveyskirjasto health library: Kalsium (P-Ca, Ca-albk ja Ca-Ion) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=snk03063&p_hakusana=kalsium
Terveyskirjasto health library: Kalsium – liikaa (hyperkalsemia) tai liian vähän (hypokalsemia) veressä https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=dlk00025
Luustoliitto: Kalsium https://luustoliitto.fi/tietoa-luustosta/lapsille-ja-nuorille/ravinto/kalsium/
Luustoliitto: Kalsium https://luustoliitto.fi/osteoporoosin-itsehoitopolku/omahoidon-kokonaisuus/kalsium/
Fasting is not required
This examination does not require fasting