Vitamin B12 (Cobalamin)
Vitamin B12 is a water-soluble vitamin essential for DNA synthesis, red blood cell formation, and nerve function. It is found almost exclusively in animal-derived foods. The body stores 2–5 years' worth of B12 in the liver, so deficiency develops slowly. B12 deficiency is extremely common in India, particularly among vegetarians.
Reference Ranges
Male
200 – 900
pg/mL
Female
200 – 900
pg/mL
Child
200 – 900
pg/mL
Ages 1–18
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low B12 causes megaloblastic anemia (large, immature red blood cells) and neurological damage — numbness, tingling in hands and feet, difficulty walking, memory problems, and depression. Neurological damage can become irreversible if untreated. Common causes include vegetarian diet, pernicious anemia (autoimmune), and malabsorption (atrophic gastritis, metformin use).
What High Levels Mean
High B12 is usually harmless and can result from supplementation, liver disease, or kidney disease. Very high levels (>1000 pg/mL) without supplementation may occasionally indicate blood cancers (chronic myeloid leukemia) or liver damage. B12 supplements cannot cause toxicity — the body excretes excess.
Frequently Asked Questions
Why are vegetarians at risk for B12 deficiency?
Vitamin B12 is naturally found only in animal products — meat, fish, eggs, and dairy. Strict vegetarians and vegans get almost no B12 from diet. Even lacto-vegetarians may not get enough, as dairy contains relatively low amounts. Supplementation or fortified foods are essential for vegetarians.
Can B12 deficiency cause permanent nerve damage?
Yes, if untreated for months to years. B12 is required for myelin (the insulating sheath around nerves). Prolonged deficiency causes demyelination — numbness, tingling, balance problems, and cognitive decline. While early symptoms are reversible with treatment, long-standing damage may be permanent.
Is it possible to have B12 deficiency with normal levels?
Yes. Some people have functional B12 deficiency — normal blood levels but cellular deficiency. Testing methylmalonic acid (MMA) and homocysteine can reveal functional deficiency even when serum B12 appears normal. Symptoms despite normal B12 warrant these additional tests.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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