From North Central Oklahoma Ostomy Outlook September 2008:

Vitamin B-12 Replacement Therapy

by Bob Baumel, Ostomy Association of North Central Oklahoma

Editor’s note: This is an updated version of an article that I originally prepared for our November 2005 newsletter. That original article can still be viewed at

Editor’s note 2: We ran this article again in our March 2016 newsletter and modified the text slightly. Consequently, I’ve updated the text below to match the version in our March 2016 newsletter. Please note, however, that this online version includes Further Reading links at the bottom that weren’t included in our newsletter.

Vitamin B-12 is, under normal conditions, absorbed in only a small section of the terminal small intestine (ileum), raising the possibility of B-12 deficiency if that section of ileum has been removed surgically or damaged by disease. People who may have lost that portion of ileum include some ileostomates, people who had a failed J-pouch or Kock pouch, and some people with urinary diversions (especially continent urinary diversions) made using the terminal ileum. A condition such as Crohn’s disease may have damaged the terminal ileum, even if it hasn’t been removed surgically.

Vitamin B-12 is necessary for many metabolic processes including development of red blood cells, and also maintains normal functioning of the nervous system. Deficiency causes anemia (reduced oxygen carrying capacity of the blood resulting in fatigue) and can also cause nervous system damage. It’s worth noting that folic acid (another B vitamin) can correct the anemia caused by vitamin B-12 deficiency but will not correct the nerve damage caused by B-12 deficiency. So it’s important to get enough vitamin B-12.

If you think you are at risk for vitamin B-12 deficiency, you can ask your doctor to check your serum (blood) B-12 level. This test can be added easily to routine blood testing. If your ability to absorb vitamin B-12 by the normal pathway involving the terminal ileum has been impaired, you can supplement the vitamin by three basic methods:

By injection: This method bypasses the normal gastrointestinal process of B-12 absorption by inserting it into the body by intramuscular or subcutaneous injection. In cases of serious B-12 deficiency, this method should be used first in order to build up the B-12 level as rapidly as possible; then, the patient may switch to one of the other methods if desired. B-12 injections may be self-administered in the same way that diabetic patients can give themselves insulin shots. Maintenance therapy may require only one B-12 injection per month.

Nasally: This method also bypasses the normal gastrointestinal absorption process, as vitamin B-12 can be absorbed through nasal mucous membranes. The nasal form of B-12 was developed first as a nasally applied gel and later a true nasal spray (brand name Nascobal®). This product is marketed by the company Par Specialty Pharmaceuticals, who promotes it as the only FDA approved form of vitamin B-12 besides the injectable form (Note: FDA approval isn’t relevant to oral B-12, discussed below, because the FDA doesn’t regulate oral vitamin sales). Nasal B-12 can be effective but, because one company has sole rights to distribute it in the U.S., it can be an expensive way to get your vitamin B-12.

Orally: Until recently, doctors believed that B-12 taken orally was useless to people who lack the normal absorption mechanism involving the terminal ileum. That opinion has changed, however, as research has revealed that even in such people, when a large dose of vitamin B-12 is taken orally, a small fraction (typically around 1%) gets absorbed by passive diffusion through the gut. Therefore, you may absorb an adequate amount of B-12 by taking a big enough oral dose—a typical recommended dosage is 1000 micrograms per day. Vitamin B-12 tablets in large sizes of 1000 micrograms or more are available inexpensively without a prescription and are also quite safe (there is no known toxicity to vitamin B-12, even in considerably larger dosages, and even in people with normal ability to absorb the vitamin). Oral B-12 can thus be a safe, easy and effective way to get the vitamin. It may not work, however, in people with a severely shortened intestine (short bowel syndrome), who may therefore have to use one of the first two methods listed above.

Notes on Oral Forms of Vitamin B-12

Many of the available oral preparations of vitamin B-12 in sizes of 1000 micrograms or more are marked as either “sublingual” or “time release.” The time release versions should definitely be avoided. Considering the small fraction of vitamin B-12 that gets absorbed (in people who lack the normal pathway for B-12 absorption), delaying that absorption further makes no sense. The sublingual versions do “work,” although there’s no evidence that this vitamin can be absorbed through membranes under the tongue, so the “sublingual” form is basically a gimmick. Effectiveness of oral B-12 depends only on the dosage. So you can just buy the lowest cost version available at the desired dosage (whether a “sublingual” form or regular tablets), as long as it isn’t a time release preparation.

Further Reading

National Institutes of Health Fact Sheet:
American Family Physician article:
Wikipedia article on Vitamin B12

Research article abstracts (cited in above Wikipedia article)

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This page last revised 2016-05-02
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