Leftover crabs if overnight over a long time can not then heat a hot meal, preserved properly and can heat a hot meal. 1. can not eat: general leftover crab at room temperature overnight will breed a lot of bacteria, and then eat may cause bacterial infection resulting in abdominal pain, diarrhea and other abdominal discomfort, will seriously endanger the health of the body. 2. can eat: leftover crab is not overnight or in the refrigerator properly preserved, you can heat a hot meal, but pay attention to eat before the heat through, to avoid residual bacteria into the body is not conducive to human health. If you feel unwell after consuming leftover crabs, stop eating immediately, go to the hospital for checkups and follow the doctor’s instructions for treatment. It is recommended that crabs should not be eaten overnight, and should be consumed on the same day. Those who are allergic to crabs should not consume crabs.