Normal vitamin D level in the blood

Each laboratory must establish its own normal ranges for vitamin D 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.

Vitamin D levels depend on the exposure to the sunlight. They show seasonal variation with the highest concentrations in summer or fall and the lowest concentrations in winter or spring. In addition, the production of vitamin D has been reported to decrease with age.

The values shown above refer to the 25-hydroxy vitamin D [25(OH)D] test which is the main circulating form of vitamin D in the blood. However, there is also a test to measure the 1,25-dihydroxyvitamin D [1,25(OH)2D] in the blood and the normal ranges for it are 15 to 60 pg/mL (36 to 144 pmol/L).

Vitamin D, also called calciferol, is a fat-soluble vitamin essential for the normal development of bones and teeth.

Contrary to its name, vitamin D is actually not a vitamin, but a hormone with an important role in the body:

• It is required for the absorption of calcium and phosphorus by the intestinal tract (and magnesium in a lesser degree).
• Protects against muscle weakness
• It is involved in regulation of heartbeat

Vitamin D is obtained in two ways:

• Endogenous: Exposure of skin to sunlight
• Exogenous: Absorbed from foods and supplements

Vitamin D is known as the sunshine vitamin because it is produced when the skin is exposed to sunlight.

Vitamin D can be categorized as:

• Vitamin D3 or cholecalciferol: Can be obtained from animal sources and it is transformed into vitamin D in the skin on exposure to the ultraviolet portion of sunlight.
• Vitamin D2 or ergocalciferols: It is present in plants and yeasts.

Only a few foods have a significant amount of vitamin D such as fish liver oils, fatty fish (sardines, mackerel, trout and salmon), egg yolks, liver, and dairy products. There are also foods supplemented with vitamin D like cereals.

Vitamin D is metabolized first in the liver to its main circulating form, 25-hydroxyvitamin D [25(OH) D] and then in the kidneys to its biologically active form, 1,25-dihydroxyvitamin D [1,25(OH)2D], a hormone regulating calcium and phosphate metabolism.

Vitamin D deficiency results in impaired formation of the bones, producing rickets in children and osteomalacia in adults.

The vitamin D values shown when doing a blood test are usually the 25-hydroxy vitamin D [25(OH)D] values. This is the main circulating form of vitamin D in the blood. The 25(OH)D value hardly change day-to-day, with exposure to sunlight or with dietary intake and the measurement is relatively easy.

The vitamin D blood test is asked and may be a help in case of suffering:

• Bone problems or disease (osteoporosis, bone fractures, etc.)
• Hypocalcemia (low level of calcium in the blood)
• Low or limited exposure to sunlight

A high level of vitamin D in the blood is not common and may be related to vitamin D toxicity due to a daily use of high-dose vitamin D supplements.

A low value of vitamin D in the blood may be related to a low intake of vitamin D or a low exposure to sunlight.

The following values are considered to be normal values:

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