Zinc sulfate is an inorganic compound and dietary supplement. As a supplement it is used to treat zinc deficiency and to prevent the condition in those at high risk. Side effects of excess supplementation may include abdominal pain, vomiting, headache, and tiredness. It has the formula ZnSO4 as well as any of three hydrates.It was historically known as "white vitriol". All of the various forms are colourless solids. The heptahydrate form is commonly encountered.