A common substance lost in sweat, besides water, is electrolytes. The main electrolytes that are secreted in sweat include sodium and chloride, with smaller amounts of potassium and other minerals. In addition, some metabolic byproducts such as lactate (lactic acid) and trace metabolites may also be present in sweat. This combination helps explain why heavy sweating can disrupt electrolyte balance and hydration status if not replenished.