Statins lower cholesterol by blocking an enzyme in the liver called HMG-CoA reductase. That enzyme is the rate-limiting step in cholesterol synthesis, so blocking it reduces the liver's cholesterol production and triggers the liver to pull more LDL cholesterol out of the blood. The result is a 30 to 50 percent reduction in LDL, depending on the statin and the dose. For people at high risk of heart attack or stroke, statins reduce the chance of a major cardiovascular event by roughly a quarter to a third.

Atorvastatin, rosuvastatin, and simvastatin are among the most prescribed drugs in the world. They are generally well tolerated, but muscle aches are a common complaint. Rarely, statins cause rhabdomyolysis, a serious muscle breakdown. Liver enzyme elevations can occur, and blood sugar may rise slightly. The benefits outweigh the risks for most people with established cardiovascular disease or high LDL. For those at lower risk, the decision is more nuanced and depends on overall risk factors.

What statins do:

• Lower LDL. Reduce the "bad" cholesterol.
• Reduce cardiovascular events. Heart attacks, strokes, and deaths.
• Stabilize plaques. Make atherosclerotic plaques less likely to rupture.
• Reduce inflammation. Some statins have anti-inflammatory effects independent of cholesterol lowering.

Statins are usually taken once daily, often at night, because cholesterol synthesis peaks overnight.