Vitamins are needed in small amounts for the body to function properly. Often vitamins are needed to manufacture proteins or tissues within the body. Vitamin deficiencies can cause a variety of health issues, depending on what is lacking. A deficiency in vitamin B12 can cause nerve problems and fatigue if levels get abnormally low.
Indications
If you develop anemia or sudden changes in mental status, a doctor may measure your levels of vitamin B12. Low levels can cause macrocytic anemia, in which red blood cells are unusually large and present in lower levels in the blood, Lab Tests Online explains. A deficiency in vitamin B12 can also cause neurological problems resulting in abnormal behavior or confusion and lethargy.
Preparation
You should not eat or drink anything for six to eight hours before taking a vitamin B12 test. This will keep you from inadvertently eating something that could cause a temporary rise in vitamin B12 levels. Your doctor will also need to know about any medications, including herbal and over-the-counter drugs, that you are taking because these could also alter the results of a vitamin B12 test, the New York Times explains. For example, phenytoin, neomycin, colchicine and para-aminosalicylic acid can all affect the results of the test.
Test
Vitamin B12 testing is done on a blood sample that is usually obtained from a vein in the arm. An elastic band will be placed on your upper arm to help the vein swell with blood. A nurse or other medical professional will insert a needle in your arm, which will then suck up the blood into an airtight vial or tube, MedlinePlus reports. The elastic band and needle will be removed and the puncture site will be covered with a bandage.
Levels
Normal vitamin B12 levels in the blood are between 200 pg/mL and 900 pg/mL. Unusually low vitamin B12 levels can be caused by a lack of vitamin B12 in the diet, pregnancy, hyperthyroidism, or conditions which interfere with vitamin B12 absorption. In order for the digestive tract to absorb vitamin B12, a protein known as intrinsic factor needs to be made; sometimes the lack of intrinsic factor can cause unusually low vitamin B12 levels.
Risks
There are very few risks involved in having your vitamin B12 levels tested. You may develop bleeding under the skin, also known as a hematoma, or an infection at the puncture site. Patients may also faint or have problems with excessive bleeding. Serious medical problems caused by venous blood draws are rare, however.
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