1. Patients without known hematologic disease were given 8 µg. (0.2 µc. Co60 vitamin B12 as a water solution or in various types of delayed release capsules.
2. All groups showed approximately equal fecal excretion. However, the cobalt60-labeled vitamin B12 delayed release capsules showed a greater urinary excretion after a loading dose of stable B12 than did the water solution of labeled vitamin B12.