Is my Vitamin B12 normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal B12 level?
Vitamin B12 is essential for nerve function, DNA synthesis, and red blood cell production. Deficiency is common — affecting up to 6% of adults under 60 and 15% of those over 60 — and causes fatigue, numbness, cognitive decline, and megaloblastic anemia. Normal is 200-900 pg/mL, but levels below 400 pg/mL may already indicate subclinical deficiency.
| Range | Values |
|---|---|
| Standard Reference | 200–900 pg/mL |
| Optimal | 400–900 pg/mL |
| Longevity Optimal | > 400 pg/mL |
| Low Risk | < 200 pg/mL |
What causes abnormal B12 levels?
Low B12 is caused by inadequate dietary intake (vegetarian/vegan diets), malabsorption (pernicious anemia, celiac disease, Crohn's, gastric bypass), aging (reduced intrinsic factor after 50), and medications (metformin, PPIs like omeprazole). Nitrous oxide exposure can also rapidly deplete B12.
When should you see a doctor?
See your doctor if B12 is below 300 pg/mL with symptoms like fatigue, numbness/tingling in hands or feet, difficulty walking, cognitive changes, or a swollen tongue. B12 deficiency can cause irreversible nerve damage if untreated. Also test methylmalonic acid (MMA) for confirmation.
B12 and longevity
B12 deficiency is increasingly recognized as a contributor to cognitive decline and neurodegeneration — even at levels previously considered "normal." Subclinical B12 deficiency (200-400 pg/mL) is associated with elevated homocysteine, brain atrophy, and accelerated cognitive aging. The gut's ability to absorb B12 diminishes with age due to declining intrinsic factor production and reduced stomach acid, making supplementation increasingly important after age 50. Methylcobalamin (the active coenzyme form) is preferred over cyanocobalamin for supplementation. B12, folate, and B6 work as a triad to metabolize homocysteine — deficiency in any one of these raises homocysteine, an independent cardiovascular and neurological risk factor.
Where to get a B12 test
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Related biomarkers
These biomarkers are often tested alongside B12 for a more complete picture.
Frequently asked questions
What is a normal B12 level?
Who is at risk for B12 deficiency?
How do I supplement B12?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.