Perioperative unexpected hypothermia (IPH) and excessive preoperative fasting and no drinking are commonly seen in the perioperative period and closely associated with a variety of complications. However, the clinical correlation between IPH and excessive preoperative fasting and no drinking is still unclear. This article describes IPH, and discusses its mechanisms and influencing factors, the current status of preoperative fasting and no drinking, and the potential mechanisms by which excessive fasting and no drinking may lead to IPH, in order to raise the awareness of clinicians to excessive fasting and no drinking and its damages, and to timely identify patients with a high risk of IPH and provide individualized interventions in advance.