Form Comparison

Adenosylcobalamin vs Cyanocobalamin

How adenosylcobalamin and cyanocobalamin differ in potency, absorption, tolerance, and cost.

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Quick verdict. Cyanocobalamin is the studied, stable, cheap default, and cells convert it into both active cofactors, adenosylcobalamin and methylcobalamin. Oral adenosylcobalamin has sparse human data on its own. Choose cyanocobalamin for treating or preventing deficiency, and adenosylcobalamin only as part of a combined methyl and adenosyl product you already want.

Side by Side

Adenosylcobalamin Cyanocobalamin
Absorption Moderate High
How it is absorbed Same uptake pathways. Mitochondrial cofactor for methylmalonyl-CoA mutase. Bound by intrinsic factor and absorbed in the terminal ileum; this route saturates at about 1.5-2 mcg per dose. About 1% of a large oral dose also crosses by passive diffusion, which is why 1,000 mcg oral doses work even without intrinsic factor.
Typical dose 500-1,000 mcg daily, often combined with methylcobalamin 25-1,000 mcg daily; 1,000-2,000 mcg for malabsorption
Common uses combination B12 products general supplementation, deficiency treatment, fortified foods
Side effects Very well tolerated. Very well tolerated. The cyanide content is toxicologically trivial.
Cost High Low
Also called dibencozide, cobamamide vitamin B12
Labels in index 115 871

When to Choose Adenosylcobalamin

Choose adenosylcobalamin when it is part of a combined methyl and adenosyl product you already want. Human data comparing it to other oral forms are sparse.

Adenosylcobalamin

Choose adenosylcobalamin when it is part of a combined methyl and adenosyl product you already want.

What to look for: Adenosylcobalamin named on the Supplement Facts panel, with the amount per serving stated.

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When to Choose Cyanocobalamin

Choose cyanocobalamin when you want the most studied, stable, and cheapest form. Synthetic and the most stable form. Converted in cells to methylcobalamin and adenosylcobalamin. Most clinical trials used it.

Cyanocobalamin

The best-studied oral form and the one used in the trials of high-dose oral therapy. Stable and inexpensive.

What to look for: 1,000 mcg tablets for malabsorption or treatment; 25-100 mcg daily for vegans with normal absorption.

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Products on Titrate

In Titrate's index of NIH label data, 115 labels named as vitamin B12 products list adenosylcobalamin and 871 list cyanocobalamin.

Open supplement search

Supplement Search loads one category at a time. Choose the B-Complex tab, then type a form such as "cyanocobalamin" under Must contain, or a form to avoid under Must not contain.

Related

References

NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals.

Berlin H, Berlin R, Brante G. Oral treatment of pernicious anemia with high doses of vitamin B12 without intrinsic factor. Acta Med Scand. 1968;184(4):247-258.

Stabler SP. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149-160.

Lam JR, et al. Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency. JAMA. 2013;310(22):2435-2442.

Aroda VR, et al. Long-term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study. J Clin Endocrinol Metab. 2016;101(4):1754-1761.

Wang H, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. 2018;3(3):CD004655.