The first signs of niacin deficiency are all of the following EXCEPT dermatitis anorexia indigestion weakness Solution Answer is dermatitis The early stage signs and symptoms of niacin deficiency are Weakness Headache Indigestion, Anorexia, Fatigue, Headache Mild skin eruptions, Backache Weight loss. Only in the advanced stage, the person will get scaly dermatitis. So dermatitis is not the early sign of niacin deficiency..