Vitamin and mineral supplements are important for gastric bypass patients because deficiencies can develop. The most vital gastric bypass supplements include calcium, iron and vitamin B-12. Gastric bypass surgery can cause dizziness, fatigue and low blood. Iron supplements can help eliminate these deficiencies. Calcium helps strengthen bones which may become weakened after surgery. Vitamin B-12 is essential for regenerating red blood cells, and it helps rebuild and strengthen muscles. B-12 also helps the central nervous system to function properly. Other benefits of vitamin B-12 include the improvement of memory, balance and concentration. Multivitamins are also important for maintaining overall good health.