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Vitamin B12 Blood Test: What Your Results Mean

Vitamin B12 is essential for nerve function, DNA synthesis, and red blood cell formation. Deficiency develops slowly over months or years and can cause irreversible neurological damage if left untreated. It is especially common in vegetarians, vegans, and older adults.

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Normal Range

200 – 900 pg/mL

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Unit

pg/mL

What Your Results Mean

Normal

Normal B12 levels support healthy nerve function, energy production, and red blood cell formation, reducing the risk of megaloblastic anemia and neurological complications.

High

High B12 is rarely dangerous from diet or supplements, but very high levels without supplementation can indicate liver disease, certain blood cancers, or kidney problems.

Low

Low B12 causes fatigue, weakness, numbness and tingling in hands and feet, balance problems, memory issues, depression, and megaloblastic anemia. Neurological damage can be irreversible.

Frequently Asked Questions

What is a normal B12 level? expand_more

Normal B12 is 200–900 pg/mL. Levels below 200 pg/mL indicate deficiency, while 200–300 pg/mL is considered borderline low by many clinicians.

Who is at risk of B12 deficiency? expand_more

Vegans and vegetarians, people over 50 (reduced stomach acid), those with pernicious anemia, Crohn's disease, celiac disease, or those taking metformin or proton pump inhibitors long-term.

How do I treat B12 deficiency? expand_more

Oral B12 supplements (1,000 mcg daily) are effective for dietary deficiency. Pernicious anemia or severe deficiency may require B12 injections.

What foods are high in B12? expand_more

Meat, fish, shellfish, eggs, dairy products, and fortified cereals are the best sources. Plant-based sources are very limited, making supplementation essential for vegans.

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