What Is a Low Level of Vitamin B12?

by Matthew Busse

About Matthew Busse

Matthew Busse has pursued professional health and science writing since 2007, writing for national publications including "Science Magazine," "New Scientist" and "The Scientist." Busse holds a doctorate in molecular biology from the University of California-San Diego.

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Vitamin B-12 is a fat-soluble nutrient required for several crucial biochemical processes in your body, including neuronal firing, red blood cell synthesis and DNA replication. A deficiency in vitamin B-12 could result in severe health problems. If your doctor suspects you have a vitamin B-12 deficiency, a blood test can determine how much of this vitamin is present in your blood stream.

Vitamin B-12 Level

The normal concentration of vitamin B-12 in the blood ranges from around 170 picograms per milliliter, or pg/ml, to 900 pg/ml, reports the Office of Dietary Supplements of the National Institutes of Health. In adults, levels below 170 pg/ml are typically considered an indication of vitamin B-12 deficiency.

Vitamin B-12 Blood Test

The standard test of vitamin B-12 levels requires drawing blood from a vein, usually at on the back of the hand or the inside of the elbow. Before taking the test, you will need to refrain from drinking and eating anything for six to eight hours. Be sure to tell your doctor about any medications your are taking, including herbal and over-the-counter medications, because certain medications may affect the test results.

Blood Levels Versus Intracellular Levels

The most common tests of vitamin B-12 levels measure the concentration of vitamin B-12 in your blood serum or blood plasma, two different components of blood. However, levels of vitamin B-12 in your blood may not accurately reflect the levels of the vitamin within actual cells. While there are other tests that indirectly measure levels of vitamin B-12 within cells, they are not entirely accurate for other reasons. As a result, the blood test is still the standard test for measuring vitamin B-12 levels.

Recommended Dietary Allowance

The Food and Nutrition board of the Institute of Medicine has developed a Recommended Dietary Allowance, or RDA, for vitamin B-12. Based on available research, consuming the RDA each day should prevent low levels of vitamin B-12 from developing. For adults ages 14 years and older, the RDA for vitamin B-12 is 2.4 micrograms per day. The RDA decreases with age for children, down to 0.4 micrograms per day for infants less than 6 months old.

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