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Vitamin B12

Published: July 27, 2026Updated: August 25, 2026

Vitamin B12 is a crucial nutrient that supports nerve function and the production of red blood cells.

Quick summary

Vitamin B12 levels indicate potential deficiencies or excesses affecting blood and nerve health.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
pg/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche Vitamin B12, Abbott Vitamin B12, Siemens Vitamin B12
interpretation: {"text":"May indicate pernicious anemia, malabsorption, or dietary deficiency. Symptoms can include fatigue, weakness, and neurological problems.","label":"Low Vitamin B12"}; {"text":"Could suggest liver disease, certain types of leukemia, or excessive supplementation. Further testing is often required to determine the cause.","label":"High Vitamin B12"}

Vitamin B12, also known as cobalamin, is essential for DNA synthesis, neurological function, and the formation of red blood cells. Its measurement in the blood helps diagnose deficiencies that can lead to anemia and neurological issues.

Normal levels of Vitamin B12 typically range from 200 to 900 pg/mL. Levels below this range may indicate a deficiency, while higher levels could suggest liver disease or other conditions.

Deficiency in Vitamin B12 is commonly associated with pernicious anemia, malabsorption syndromes, and dietary insufficiency, particularly in vegetarians and vegans.

Frequently asked questions

What are the symptoms of Vitamin B12 deficiency?
Symptoms include fatigue, weakness, constipation, loss of appetite, and neurological changes such as numbness and tingling in the hands and feet.
How can I increase my Vitamin B12 levels?
Consuming foods rich in Vitamin B12, such as meat, fish, eggs, and dairy products, or taking supplements can help increase levels. In some cases, injections may be necessary.
  1. 1
    Vitamin B12 - Mayo ClinicSource
  2. 2
    Vitamin B12 Deficiency - National Institutes of HealthSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy