Reheating cooked chicken can be done safely and effectively as long as it is done properly. 

First, the chicken should be heated gently. It’s best to reheat the chicken slowly at a low temperature of 165°F (74°C) or less for several minutes, until an internal temperature of 165°F (74°C) has been reached throughout the entire piece. Heating quickly at high temperatures can dry out the meat and make it tough, so slow cooking is key! 

It's important to avoid reheating leftover chicken more than once as this increases your risk of food poisoning. Any leftovers should always be refrigerated within two hours after cooking and eaten within three to four days after cooking. If you aren’t planning on eating all of your cooked chicken in that time frame, freeze it for longer storage. 

When reheating frozen or thawed leftover cooked chicken, you need to make sure that there are no signs of spoilage such as an unpleasant odor or a slimy texture before consuming it. Also check to see if any stores mishandled any raw poultry products prior to purchase; if so throw them away immediately for safety reasons. And finally, never eat raw or undercooked poultry products – cook them thoroughly by using a thermometer until they reach an internal temperature between 74-82ºC/165-180ºF throughout each piece before eating them!