Vitamin B1, also called thiamine, is a water-soluble vitamin and is particularly essential for the functioning of the nervous system. Since vitamin B1 is essential for the formation of the hormone serotonin, it is also popularly called the mood vitamin.When can Vitamin B1 AGEPHA be used?In the case of vitamin B1 deficiency and associated diseases in case, it cannot be remedied by nutritional intake. Vitamin B1 deficiency results from decreased intake in the digestive tract or increased demand during pregnancy and lactation, growth, exercise, and metabolic activity.