Nascobal is a synthetic form of vitamin B12. It is used in the treatment of vitamin B12 deficiency in the body. Vitamin B12 is important because it enables the body to utilize carbohydrates and fats for energy and synthesize new proteins. It is also essential for healthy cells, nerves and blood. Nascobal works by replacing the normal Vitamin B12 in the body, thereby eliminating vitamin B12 deficiency.