Cyanocobalamin is a vitamin also known as B12
October 12 2016 by Ray Sahelian, M.D.

Vitamin B-12 is the name for a whole group of chemicals with B-12 activity, and cyanocobalamin is one of these. Cyanocobalamin usually does not even occur in nature, and is not one of the forms of the vitamin which is directly used in the human body. Humans can convert it to active (cofactor) forms of the vitamin, such as methylcobalamin.

Q. I'm a bit confused regarding the forms of vitamin B12 specifically cyanocobalamin vs. methylcolbamin. Is the latter a coenzyme of the former and are they interchangeable in terms of use. Specifically is the methyl form useful for those suffering from anemia.

Q. I was reading about vitamin B12. Regarding cyanocobalamin and cyanide a web site says:  To the best of our understanding, cyano refers to (-CN). Cyanocobalamin is a synthetic form of vitamin B12. What does (-CN) mean? Does it stand for cyanide? Also, is cyanocobalamin synthetic? One of the other answers says it's natural.
   A. I have not seen enough research yet to determine the difference in activity between the two forms. At this time the use of methylcobalamin is well understood and I would suggest using this form although cyanocobalamin appears to be safe, also.

Hong Kong Medical J. 2015. Vitamin B12 deficiency in the elderly: is it worth screening? Vitamin B12 deficiency is common among the elderly. Elderly people are particularly at risk of vitamin B12 deficiency because of the high prevalence of atrophic gastritis-associated food-cobalamin (vitamin B12) malabsorption, and the increasing prevalence of pernicious anaemia with advancing age. The deficiency most often goes unrecognised because the clinical manifestations are highly variable, often subtle and non-specific, but if left undiagnosed the consequences can be serious. Diagnosis of vitamin B12 deficiency, however, is not straightforward as laboratory tests have certain limitations. Setting a cut-off level to define serum vitamin B12 deficiency is difficult; though homocysteine and methylmalonic acid are more sensitive for vitamin B12 deficiency, it may give false result in some conditions and the reference intervals are not standardised. At present, there is no consensus or guideline for diagnosis of this deficiency. It is most often based on the clinical symptoms together with laboratory assessment (low serum vitamin B12 level and elevated serum homocysteine or methylmalonic acid level) and the response to treatment to make definitive diagnosis. Treatment and replacement with oral vitamin B12 can be as effective as parenteral administration even in patients with pernicious anaemia. The suggested oral vitamin B12 dose is 1 mg daily for a month, and then maintenance dose of 125 to 250 g for patients with dietary insufficiency and 1 mg daily for those with pernicious anaemia.

Assessment of Vitamin B12 Absorption Based on the Accumulation of Orally Administered Cyanocobalamin on Transcobalamin.
Clin Chem. 2009. Hardlei TF, Mrkbak AL, Bor MVE. Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus Hospital, Aarhus, Denmark.
Vitamin B12, or cobalamin (Cbl), is absorbed in the intestine and transported to the cells bound to transcobalamin (TC). We hypothesize that cyanocobalamin is absorbed unchanged, thereby allowing measurement of the complex of cyanocobalamin bound to TC (TC-CNCbl) to be used for studying the absorption of the vitamin. TC was immunoprecipitated from serum samples obtained from healthy donors at baseline and at 24 h after oral administration of three 9-mug CNCbl doses over 1 day. Cbl was released by treatment with subtilisin Carlsberg. The different forms of Cbl were isolated by HPLC and subsequently quantified with an ELISA-based Cbl assay. At baseline, the median TC-cyanocobalamin concentration was 1 pmol/L; the intraindividual variation (SD) was 1.6 pmol/L. After CNCbl administration, the TC-CNCbl concentration increased significantly, whereas no major changes were observed in any of the other Cbl forms bound to TC. Only a moderate additional increase in TC-CNCbl was observed with prolonged (5 days) CNCbl administration. We designed an absorption test based on measuring TC-CNCbl at baseline and 24 h after CNCbl intake and established a reference interval for the increase in TC-CNCbl. The median absolute increase was 23 pmol/L (range, 6-64 pmol/L), and the relative increase was >3-fold. Our data demonstrate that CNCbl is absorbed unchanged and accumulates on circulating TC. We suggest that measuring TC cyanocobalamin will improve the assessment of vitamin B12 absorption.