Home made, cooked lasagna keeps in the refrigerator for three to five days. It is important to cover and refrigerate the lasagna within two hours of cooking it. Lasagna keeps in the freezer for one to two months.
If the cooked lasagna is meant to be refrigerated, it is best to allow it to cool completely putting it in the refrigerator. A warm dish in the refrigerator raises the overall internal temperature of the refrigerator. The food should be covered firmly with kitchen foil, or it should be transferred to an airtight container and covered. If it is a commercially frozen lasagna, it should be kept in the freezer until it is taken out to be cooked. Once it has been cooked, the leftover lasagna can be kept safely in the refrigerator for up to two days in a covered container.