Vitamin D25 is a type of vitamin D that can be measured by a blood test. It is converted to the active form, D1,25, which helps control calcium and phosphate levels in the body. Vitamin D25 is obtained through diet or sunlight, and low levels can indicate a deficiency or absorption problem. Testing for both vitamin D25 and D1,25 is necessary for a diagnosis, and certain medications can affect absorption. High levels of vitamin D25 can indicate excessive supplementation.
Vitamin D25 is an abbreviated name for 25-hydroxy-vitamin D, one of two types of vitamin D that can be measured by a blood test. When a doctor orders a blood test, it will be tested for vitamin D25, and sometimes the second form of vitamin D, called 1,25D-dihydroxy-vitamin D (D1,25), will also be tested. Known as an inactive element in the body, vitamin D25 is sometimes called a prehormone because it is converted to the D1,25 hormone. This conversion process takes place in the kidneys, and the active form, D1,25, helps control calcium and phosphate levels in the body.
Two main components of vitamin D25 are D3, also called cholecarciferol, and D2, also called ergocalciferol. Humans ingest natural D3 when they eat animal foods, such as fatty fish and egg yolks, while synthetic D3 is often added to yogurt and milk, as well as breads and cereals. D3 can also be obtained through exposure to sunlight. D2 comes from plant foods like mushrooms.
Doctors order vitamin D blood tests when they suspect a patient has a deficiency or a problem with the parathyroid glands, which play a role in converting vitamin D25 to vitamin D1,25. When vitamin D25 levels are low, the patient may not get enough D3 and D2 from dietary sources and/or from the sun. Low levels can also mean that the patient has a problem absorbing vitamin D25, even if they are taking adequate amounts. High levels of this type of vitamin D sometimes indicate that a patient is getting too much of the vitamin from supplements.
When a doctor orders a concurrent vitamin D1,25 test, and the result shows a low reading, the patient is evaluated for kidney disease or parathyroid problems. When the D1.25 reading is very high, some diseases may be the cause, including lymphoma and an autoimmune condition called sarcoidosis. In cases where the vitamin D25 reading is very low and the vitamin D1,25 is very high, doctors try to determine what disease process might be causing the results. Supplemental vitamin D should be avoided until the doctor understands the cause of very low vitamin D25 combined with very high D1.25.
The relationship between the two forms of vitamin D is complex. Without testing for both elements, a diagnosis cannot be reached. Also, when vitamin D malabsorption is suspected, some medications may be to blame, including the anticonvulsants phenytoin and phenobarbital and the antibiotic rifampicin.
Protect your devices with Threat Protection by NordVPN
