Meatloaf, unlike a creamy casserole with a lot of liquid ignredients, is likely to dry out if reheated after having already been cooked. So it's better to combine the meat mixture, form into a loaf, and freeze it before cooking. To bake a frozen loaf, use the method given in your recipe, but bake 1-1/2 to 2 times longer. Always check for doneness with a meat thermometer and make sure the meatloaf has reached a minimum of 160 degrees.
You can also freeze leftover meatloaf in individual portions. The individual portions will reheat very quickly, and therefore, without drying out. For more tips on freezing recipes, see our Fill-Up-Your-Freezer Storage Guide.