A study published in Blood (August 15, 1998; 92(4):1191–1198) compared oral and injectable vitamin B12 therapy in patients diagnosed with vitamin B12 deficiency.
The study included 38 patients, who were divided into two treatment groups. One group received intramuscular cobalamin injections at a dose of 1 milligram, administered on days 1, 3, 7, 10, 14, 21, 30, 60, and 90. The second group received oral cobalamin at a dose of 2 milligrams daily for a period of four months.
At the end of the treatment period:
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Serum cobalamin levels were higher in the group receiving oral therapy
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Homocysteine levels were lower in the oral therapy group
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Methylmalonic acid (MMA) levels were also lower in the oral therapy group
These biochemical markers are commonly used to assess functional vitamin B12 status.
Context
This study demonstrated that high-dose oral vitamin B12 was at least as effective—and in some measures more effective—than intramuscular injections in improving both serum B12 levels and functional markers of deficiency. The findings challenged the long-held assumption that injectable B12 is inherently superior, even in patients with established deficiency.
