Will a Multivitamin Cover B12 Needs?
Is a typical daily multivitamin with 100% RDA of B12, taken once a day, sufficient to reliably cover my B12 needs?
No. The RDA for vitamin B12 is 2.4 µg. I recommend getting at least 25 µg per day if only getting B12 in one dose per day.
Note that nutrition labels on supplements usually show the percentage of the Daily Value, not the RDA. The Daily Value for B12 is 6 µg, which is still not enough.
The body can absorb B12 two ways:
1. Using transport proteins that ferry B12 from the digestive tract into the blood.
2. Through passive diffusion without any transport proteins.
The transport proteins get saturated at about 1.5 µg while only 1% to 1.5% of B12 is absorbed through passive diffusion. Because of this, I recommend 25 to 100 µg if only getting B12 in one dose per day.
Vitamin B12: Are you Getting It? – How Recommendations Were Formulated
Table of Daily Recommendations – Shows amounts needed for two daily doses, one daily dose, and two weekly doses.