Aspirin works by inhibiting the function of platelets in the blood. With more than 80% of platelet function in the body inhibited, cardiovascular disease can be prevented. The body regenerates about 1/10th of its platelets every day, so taking the drug once a day will keep more than 90% of the platelets from functioning by simply keeping the newly generated, functional platelets inhibited. For these reasons, aspirin only needs to be taken once a day. So, when is this one time the best time to take it? Opinions are not unanimous as to whether aspirin is better taken in the morning or at night. Most opinions favor taking it in the morning. Because from the human body’s biological clock, 6:00-10:00 a.m., blood viscosity is higher, blood pressure, heart rate level is also high, this time is the high incidence of cardiovascular and cerebrovascular accidents. Aspirin has a faster onset of action in the body, so it is more appropriate to take it in the morning at 7:00-8:00 a.m. for the purpose of treating and preventing cardiovascular and cerebrovascular diseases. The recent American College of Chest Physicians (ACCP) evidence-based guidelines for antithrombotic and thrombolytic therapy point out that the use of aspirin for the prevention of myocardial infarction, stroke, and vascular death, the best time to take it is after breakfast, and the dosage form of aspirin enteric-coated tablets is the best. Another viewpoint is that because the body is less active at night, the blood is viscous, blood flow slows down, and platelets are easy to aggregate, so taking the drug at night may provide better efficacy. The author believes that, for most patients, due to the use of ordinary aspirin enteric-coated tablets, peak time and half-life are relatively short, to take in the morning is more appropriate; for patients taking aspirin sustained-release tablets, due to peak time and half-life are longer, it is more appropriate to take at night. Of course, the safest way is still to take under the guidance of a doctor, so that aspirin to play a better role.