What is Vitamin B12 ( Fasting )?

Also known as:Vitamin B12; cobalamin; folic acid; RBC folate

Why get tested?

To investigate the cause of anemia or neuropathy (nerve damage), to evaluate nutritional status in some patients, to monitor the effectiveness of treatment for B12 or folate deficiency

When to get tested?

When you have an abnormal full blood count with a blood film showing large red blood cells, or abnormal neutrophils; when you have symptoms of anemia and/or of neuropathy (e.g. tingling or numbness in the hands or feet); when you are being treated for B12 or folate deficiency.

Sample required?

A blood sample drawn from a vein in your arm.

WHAT IS BEING TESTED?

These tests measure the concentration of folate and vitamin B12 in the serum or plasma (liquid portion of the blood). Vitamin B12 is also known as cobalamin. The amount of folate inside the red blood cell (RBC) may also be measured - it will normally be at a higher concentration inside the cell than in the serum and reflect folate level over a longer period. Vitamin B12 and folate are two vitamins that are part of the B complex group of vitamins. Folate is found in leafy green vegetables, citrus fruits, dry beans and peas, liver, and yeast while vitamin B12 is found in animal products such as red meat, fish, poultry, milk, and eggs. Fortified cereals, bread, and other grain products are now also important dietary sources of folate (identified as 'folic acid' on nutritional labels), especially for those vegetarians who do not consume any animal products. Since September 2009, mandatory folate fortification of flour in Australia has significantly reduced the incidence of folate deficiency.

Both vitamin B12 and folate are necessary for normal red cell formation, tissue and cellular repair, and DNA synthesis. Vitamin B12 is also important for nerve health, while folate is necessary for cell division such as occurs in a rapidly growing fetus during pregnancy. A deficiency in either vitamin B12 or folate can lead to a form of anemia characterized by the production of fewer, but larger, red cells (macrocytic anemia).

A deficiency in vitamin B12 can also result in varying degrees of neuropathy, nerve damage that can cause tingling and numbness in a person's hands and feet. A deficiency in folate can cause neural tube defects such as spina bifida in a growing fetus.

B12 and folate deficiencies are most often caused by not getting enough of the vitamins through the diet or supplements, inadequate absorption, or increased need as seen in pregnancy.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

Fasting for 6-8 hours before sample collection may be required.
Fasting is essential for serum folate as food prior to testing can influence the measured serum level.