To determine if the meatloaf is cooked thoroughly, you can use an instant-read meat thermometer. Insert the thermometer into the center of the meatloaf, and it should register an internal temperature of 160°F (71°C) for ground meat to be considered safe to eat. If you don't have a thermometer, you can also check for doneness by ensuring that the meat is no longer pink in the center and the juices run clear.