The pill works, if the dose is far above a normal supplement
Oral treatment works at 1 to 2 milligrams a day, far above an ordinary supplement. At that dose, over 90 percent of both the tablet and injection groups had normal levels by week eight.
What the study found
Swallowed B12 matched the injection across 6,098 people
The catch is the dose: oral treatment works at 1 to 2 milligrams of B12 a day, far above an ordinary supplement. Give that, and in over-65s who started deficient more than 90 percent of both the tablet group and the injection group had normal blood levels by week eight.
The caveat · Blood levels, not how people felt
These trials counted blood levels, not whether anyone felt better. The Cochrane review behind the comparison had three eligible trials and 153 people, and graded its own certainty low. By one year the oral group had slipped slightly behind the injected one on the stricter analysis.