Vitamin B12 and folate

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Also known as: Vitamin B12; cobalamin; folic acid; RBC folate
Formal name: Vitamin B12, folate
Related tests: FBC

At a Glance

Why Get Tested?

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

When to Get Tested?

When you have large red blood cells, when you have symptoms of anaemia and/or of neuropathy. When you are being treated for B12 or folate deficiency

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

Fasting for 6-8 hours before sample collection is required especially for serum folate testing

The Test Sample

What is being tested?

These tests measure the concentration of folate and vitamin B12 in the serum (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 both part of the B complex group of vitamins and come from food. 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, breads 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 and increased blood folate levels. 

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 anaemia characterised by the production of fewer, but larger, red cells (macrocytic anaemia).

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

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.

The Test

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Ross D Brown, Mark R Langshaw, Elaine J Uhr, John N Gibson and Douglas E Joshua
The impact of mandatory fortification of flour with folic acid on the blood folate levels of an Australian population. MJA 20011;194(2):65-67