Form Comparison

Adenosylcobalamin vs Hydroxocobalamin

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

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Quick verdict. These rarely compete: hydroxocobalamin is the injectable form, retained longer than cyanocobalamin so injections can be spaced out, and it is the standard injection in the UK. Adenosylcobalamin is an oral mitochondrial cofactor with little comparative data. Choose hydroxocobalamin for injection-based treatment; adenosylcobalamin has no clear standalone role.

Side by Side

Adenosylcobalamin Hydroxocobalamin
Absorption Moderate High
How it is absorbed Same uptake pathways. Mitochondrial cofactor for methylmalonyl-CoA mutase. Binds plasma proteins more tightly than cyanocobalamin, so injected doses are retained longer and need less frequent dosing.
Typical dose 500-1,000 mcg daily, often combined with methylcobalamin 1,000 mcg intramuscular per protocol; 1,000 mcg oral
Common uses combination B12 products injectable B12 (standard in the UK), cyanide poisoning antidote (high dose)
Side effects Very well tolerated. Injection site pain; red urine at antidote doses.
Cost High Moderate
Also called dibencozide, cobamamide hydroxycobalamin, vitamin B12a
Labels in index 115 65

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 Hydroxocobalamin

Choose hydroxocobalamin when you are on an injection regimen and want longer intervals. The natural form produced by bacteria.

Hydroxocobalamin

Longer retention than cyanocobalamin, which is why it is the injection of choice in much of the world.

What to look for: Mainly relevant as a prescribed injection. Oral hydroxocobalamin offers no proven advantage.

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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 65 list hydroxocobalamin.

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.