Dyslipidemia refers to abnormalities in the quality and quantity of lipids in plasma. Since lipids are insoluble or slightly soluble in water, they must be bound to proteins in plasma in the form of lipoproteins, so dyslipidemia is actually manifested as dyslipoproteinemia. The prevalence of dyslipidemia is very high, with an estimated 160 million people affected in China. A lot of research data shows that dyslipidemia is closely related to coronary heart disease, stroke, obesity, hypertension, diabetes, etc. It is an independent and important risk factor for the development of cardiovascular and cerebrovascular diseases, so some scholars call it “the source of many diseases”. When dyslipidemia is detected, therapeutic lifestyle interventions should be carried out first. However, it is often necessary to rely on medication. Generally speaking, there are two types of lipid-lowering drugs: “statins” and “betablockers”. Statins are divided into natural compounds (e.g. simvastatin, pravastatin) and fully synthetic compounds (e.g. fluvastatin, atorvastatin). They are primarily cholesterol-lowering and are used to treat hypercholesterolemia. Once you suffer from hypercholesterolemia, your doctor often recommends taking lipid-lowering drugs, and by the way you will be told that the drug should be taken at night, and you will take it as your doctor tells you to, but do you know why? The key enzyme that regulates cholesterol synthesis is the rate-limiting enzyme hydroxymethylglutaryl coenzyme A (HMG- CoA) reductase. The synthesis of cholesterol in the body is inhibited by HMG-CoA reductase, and statins inhibit the activity of this enzyme, affecting the cholesterol synthesis process and thus lowering total serum cholesterol levels. Since cholesterol synthesis is strong at night, and statins work mainly by limiting cholesterol synthesis, it is best to take these drugs at night. It is also important to note that it is important not to eat at night as often as possible, as this can lead to a significant increase in cholesterol synthesis by the liver, disrupting the normal metabolism of the body and triggering or aggravating dyslipidemia. However, not all statins must be taken at night, and one of the fully synthetic compounds, atorvastatin, can be taken during the day. And why is this? It turns out that the average plasma half-life of the drug is about 14h, but due to its active metabolites, the actual half-life of HMG- CoA reductase inhibition is 20-30h, so that the drug has a long duration of action, while the half-lives of similar drugs are shorter, so it can be taken during the day. Related studies have also shown that the efficacy of daytime atorvastatin administration is not significantly different from nighttime administration, and it is more beneficial to improve the treatment and control rates because daytime administration can increase patients’ compliance with the medication. In addition, because patients with dyslipidemia require long-term medication, although this class of drugs has fewer side effects, it can cause increased transaminases or rhabdomyolysis, so it is important to follow up regularly, especially during the first 3 months of use.