Vitamin B12 Test

Vitamin B12 is a water soluble vitamin. It is also known as Cobalamin. Some of the most important functions of vitamin B12 in our body are proper functioning of brain and nervous system, blood formation, DNA synthesis and its regulation, fatty acid synthesis etc. Vitamin B12 plays a major role in the regeneration of folate in the body, thus it is possible to replace some of the effects of vitamin B12 function with sufficient level of vitamin B12 or folic acid in the body. Vitamin B12 is found in food items like meet, egg, milk and milk products, prawn, crab etc. Since vitamin B12 is found sufficiently in animal products, people who eat non vegetarian foods rarely suffer from vitamin B12 deficiency symptoms.

Vitamin B12 Level Test


Vitamin B12 test is used to measure the amount of vitamin B12 present in the body.

Description of the Test

The method followed for detecting vitamin B12 at present is more accurate than the one used few years back. Thus the change for obtaining false positive result is also very rare. This more accurate result is obtained by just carefully measuring the level of biologically active vitamin B12 in the body.

Purpose of the Test

  • Vitamin B12 level test helps in diagnosing the cause of Macrocytic anemia.
  • In case when the complete blood count test shows some abnormal results like the presence of large RBCs or low hemoglobin level, the physician may ask to do Vitamin B12 test.
  • In patients suffering from malnutrition or malabsorption, the physician may order to do vitamin B12 test along with other similar tests to confirm the condition. Some of the symptoms of vitamin B12 deficiency are weakness, fatigue etc.
  • In elderly patients, the physician may ask to perform this test to rule out the cause of behavioral changes. An abnormal level of vitamin B12 in the body may lead to behavioral changes like depression, irritability etc.
  • The vitamin B12 level test may be performed in lactating mothers whose baby is found to have vitamin B12 deficiency.
  • Physician may also ask to perform the vitamin B12 test along with other metabolic screening tests to rule out the cause of neuropathy. In some patients, the vitamin B12 deficiency may lead to some neural symptoms like numbness in the arms, tingling in the legs and so on.
  • In patients who already suffer from vitamin B12 deficiency, this test helps in ruling out the effectiveness of medication.
  • Physician may suggest performing this test in patients who is suspected of Pernicious anemia, a condition which arises due to improper absorption of vitamin B12 by the body.
  • In patients who are prone to vitamin B12 deficiency anemia, like those who have history of this anemia in their family or patients who had under gone a recent intestinal surgery or stomach surgery, the physician may order this test to diagnosis the persistence of this anemia.
  • A Patient diagnosed positive for atrophic gastritis may also be prone to vitamin B12 deficiency anemia. Thus in this case also the physician may order to perform vitamin B12 test to diagnose the condition.


The test should be done in empty stomach, thus requires fasting for about eight to ten hours. Some medicines like colchicines, methotrexate, neomysin, para amino-salicylic acid, contraceptive pills etc. may adversely affect the test result. So inform your doctor about all the medications you are undergoing before performing the test. In female patients who are pregnant or lactating, the result may be abnormal. Patients who take vitamin C in large amount may have abnormal vitamin B12 level in the body. If you have under gone any tests using dyes like Computer tomography scan, then the test result may appear abnormal.

Normal Results

The normal values of vitamin B12 may range from 200 – 900 pg/ml (pictogram per milliliter) or 146 - 616 pmol/L (picomoles per liter).

It should be noted that the normal values may vary from one lab to other depending upon the method they follow and reagents they use. So talk to your physician to know about the result interpretation.

Abnormal Results

The level of vitamin B12 less than 200pg/ml shows that the patient is vitamin B12 deficient. Such patients may show vitamin B12 deficiency symptoms like poor functioning of brain and nervous system, poor blood formation etc. Some of the major causes for vitamin B12 deficiency are:

  • Inadequate intake of vitamin B12 through diet.
  • Vitamin B12 mal absorption.
  • Pregnancy.
  • Absence of intrinsic factors needed for vitamin B12 metabolism.
  • Increased body temperature.
  • Fish tapeworm infection.
  • Surgery in the abdominal area like gastrectomy, gastric stapling surgery, removal of terminal ileum etc.

The level of vitamin B12 greater than 900pg/ml shows the presence of excess vitamin B12 in the body. But this condition occurs very rare since excess urine gets excreted out from the body through urine. Some of the major health conditions which may lead to increase in vitamin B12 level are:

  • Hepatic or liver diseases. For example: Cirrhosis, Hepatitis B etc.
  • Myeloproliferative disorders.
  • Obesity and diabetic. Obese and also diabetic people are some times found to have high level of vitamin B12 in the body.