Test for B12 Levels

Vitamin B12 levels are tested in different ways with different accuracies.

Serum B12 by radioimmune assay (RIA) is less accurate than microbial assay since it picks up all forms of cobalamin including those that are inactive. Serum B12 by microbial assay appears to be the most widely used and is considered accurate. However, pregnancy, large doses of vitamin C, and folate deficiency may result in a falsely reduced B12 microbial assay. A 24 hour urine MMA (Methylmalonic acid) test is claimed to be very sensitive but is also more expensive. Without B12, MMA increases in the urine.

Another testing pattern used by doctors to determine vitamin B12 status is to test for intrinsic factor (IF) antibodies. Their presence prevents the normal binding of B12 to IF and thus prevents B12 absorbtion. Of pernicious anemia sufferers, 70% have these antibodies. If the test for IF antibodies is negative, a Schilling test is usually performed to help distinguish the nature of the problem. This test involves the use of radioactively labelled B12 and may be objectionable to some people.

A lack of gastric hydrochloric acid tends to confirm a suspected lack of intrinsic factor (IF), as both can be due to a shrinking of gastric cells.


Test for B12 Levels can help with the following


Multiple Sclerosis / Risk

The first step when you receive a diagnosis of multiple sclerosis is to determine if you really have it. A vitamin B12 deficiency has very similar symptoms and is frequently misdiagnosed as MS; the type of anemia resulting from B12 deficiency is called pernicious anemia. [Hosp Pract (Off Ed) 1995 Jul 15;30(7): pp.47-52; discussion 52, 54]

Additionally, researchers found in 45 MS patients that vitamin B12 levels were significantly lower in those who experienced the onset of first neurological symptoms prior to age 18 years (10 patients) compared to patients in whom the disease first manifested after age 18 (35 patients). In contrast, serum folate levels were unrelated to age of onset of the disease. As vitamin B12 levels were statistically unrelated to chronicity of illness, these findings suggest a specific association between the timing of onset of first neurological symptoms of MS and vitamin B12 metabolism. In addition, since vitamin B12 is required for the formation of myelin and for immune mechanisms, a deficiency in MS is of critical pathogenetic significance. [PMID: 8407160, UI: 94011702]


Anemia, Megaloblastic

A vitamin B12 deficiency is the most common cause of megaloblastic anemia. When testing facilities are not available or cannot be afforded, intramuscular or sublingual B12, with or without folic acid, can be used to see if symptoms improve.


Obsessive-Compulsive Disorder (OCD)

In one study of OCD patients, 20% had abnormally low serum vitamin B12 concentrations compared to the two control groups. [Acta Psychiatr Scand 78(1): 8-10, 1988.]


May do some good
Highly recommended



Vitamin B-12. Essential for normal growth and functioning of all body cells, especially those of bone marrow (red blood cell formation), gastrointestinal tract and nervous system, it prevents pernicious anemia and plays a crucial part in the reproduction of every cell of the body i.e. synthesis of genetic material (DNA).


The cell-free fluid of the bloodstream. It appears in a test tube after the blood clots and is often used in expressions relating to the levels of certain compounds in the blood stream.

Vitamin C

Also known as ascorbic acid, Vitamin C is a water-soluble antioxidant vitamin essential to the body's health. When bound to other nutrients, for example calcium, it would be referred to as "calcium ascorbate". As an antioxidant, it inhibits the formation of nitrosamines (a suspected carcinogen). Vitamin C is important for maintenance of bones, teeth, collagen and blood vessels (capillaries), enhances iron absorption and red blood cell formation, helps in the utilization of carbohydrates and synthesis of fats and proteins, aids in fighting bacterial infections, and interacts with other nutrients. It is present in citrus fruits, tomatoes, berries, potatoes and fresh, green leafy vegetables.


A type of serum protein (globulin) synthesized by white blood cells of the lymphoid type in response to an antigenic (foreign substance) stimulus. Antibodies are complex substances formed to neutralize or destroy these antigens in the blood. Antibody activity normally fights infection but can be damaging in allergies and a group of diseases that are called autoimmune diseases.

Pernicious Anemia

Anemia caused by a vitamin B12 deficiency.

Hydrochloric Acid

(HCl): An inorganic acidic compound, excreted by the stomach, that aids in digestion.

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