Patients who have had gastric bypass surgery need to take 500 micrograms of vitamin B-12 each day, preferably in the morning, according to Cleveland Clinic. Tablets or sublingual doses, which dissolve under the tongue, are options. Alternately, some physicians recommend monthly injections of 1,000 micrograms of B-12.
Patients with gastric bypasses have reconstructed digestive systems and often have difficulty dealing with whole pills, states the University of California San Francisco Medical Center. Therefore, vitamin B-12 and similar tablets need to be crushed or cut into small pieces. Other vitamin and mineral supplements typically suggested for these patients include multivitamins, calcium and vitamin D.