ZocdocAnswersWhy would one take a B-12 shot?

Question

Why would one take a B-12 shot?

I'm a vegan man in my late 20s, and I keep hearing about vitamin B-12 injections. But oral supplements of vitamin B-12 are everywhere, and they're cheap. Is there an advantage to getting the B-12 shot?

Answer

Vitamin B12 deficiency should involve specialists including internists, neurologists, gastroenterologists, and others. Vitamin B12 (or cobalamin) comes from animal products (meat and dairy) for humans. Dietary vitamin B12 is made more available by stomach acids then complexed to a factor which allows it to be absorbed in the small intestine (specifically, near the end in the ileum). Problems with stomach acids, this factor, and the ileum can also lead to vitamin B12 deficiency in addition to diet. Certain causes of vitamin B12 deficiency, particularly those involving problems with absorption of vitamin B12, and not low intake, typically respond best to vitamin B12 shots. However, this method is also very effective for repleting low vitamin B12 stores even in cases of dietary deficiency to more quickly bring vitamin B12 stores back up. Oral vitamin B12 supplementation requires much higher doses for bring stores back up in vitamin B12 deficiency (1-2 mg per daily; more than 200 times higher than the minimal requirement for normal subjects). Oral formulations, when patients are compliant, are generally just as good as the shots for patients with dietary lack of vitamin B12 intake. However, due to the concern for unreliable and erratic absorption, the general recommendation is to correct vitamin B12 stores with shots with the consideration of transitioning to pills afterwards if vitamin B12 stores remain stable and normal. Additional labs in addition to vitamin B12 levels (such as homocysteine, methylmalonic acid, iron, bilirubin, LDH, folic acid and others) may be followed in order to determine the appropriateness of this. It is not possible to come to a diagnosis or treatment plan without examining the patient. The strong recommendation is to be evaluated by an internists and be seen in person.

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