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Vitamin B12 (Cobalamin)

Also known as: cobalamin, methylcobalamin, cyanocobalamin

Vitamin B12 is essential for nerve function, red blood cell formation, and DNA synthesis. Deficiency is common in vegans, the elderly, and those on metformin or proton pump inhibitors. The body can store years' worth of B12, so deficiency develops slowly.

Key Benefits

  • Prevents megaloblastic anemia
  • Supports nerve health and myelin formation
  • Essential for DNA synthesis
  • Supports energy metabolism
  • May improve mood and cognitive function

Recommended Dosage

General Use
2.4 mcg daily (RDA) — supplements typically provide 500-5000 mcg
Upper Limit
No established upper limit (water-soluble, excess excreted)
Deficiency
1000-2000 mcg daily or injections

Forms & Bioavailability

Best Forms

  • Methylcobalamin (active form)
  • Adenosylcobalamin
  • Hydroxocobalamin (injection form)

Forms to Avoid

  • Cyanocobalamin at very high doses for people with kidney issues

Safety Notes

  • Very safe even at high doses
  • Cyanocobalamin contains trace cyanide (negligible at normal doses)
  • Absorption decreases with age — sublingual or injections may be needed
  • Vegans must supplement — no reliable plant sources

Drug Interactions

Consult your healthcare provider if you take any of the following:

Metformin (reduces absorption)Proton pump inhibitorsH2 blockersColchicine

Sources

  • NIH Office of Dietary Supplements
  • American Journal of Clinical Nutrition

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