A method and device for determining whether a product is in condition to be used or consumed, this product being intended to be preserved under temperature conditions and for a period of time which limit its degradation includes an indicator combined with the product, to provide a signal indicating that the product can be used or consumed, and then, after the expiration of a preservation period of time, a signal indicating a change in the condition of possible use or consumption of the product. The period of time depends on the preservation conditions of the product. The indicator provides information enabling the product to be used or consumed for a longer period of time if the product has been preserved under conditions better than recommended conditions or for a shorter period of time if the product has been preserved under conditions worse than recommended conditions.