You can’t take cephalexin a day after drinking alcohol. Alcohol is also known as ethanol, and its clearance rate is affected by gender, age, race and other factors, and there is a 2 to 4-fold difference between different populations. Clinically applied cephalosporins can inhibit acetaldehyde dehydrogenase, an enzyme in the metabolism of ethanol, so that ethanol can not be metabolized smoothly, resulting in the accumulation of acetaldehyde, resulting in a disulfiram-like reaction. Patients manifested as facial flushing, conjunctival congestion, headache, dizziness, abdominal pain, nausea, vomiting, severe blood pressure drop, respiratory depression, heart failure and even life-threatening. Therefore, for those who really need to use cephalosporin after drinking alcohol, it should be used in accordance with medical advice. Closely observe the vital signs and clinical manifestations during the use of cephalosporin, if the above disulfiram-like reaction is found, the drug should be stopped immediately and consult a doctor.