Typically, 1,200 to 2,400 mg of red yeast rice is taken daily (two to four 600 mg pills). (Rarely, taking red yeast rice at night may cause insomnia in some people). It contains several substances that may reduce cholesterol levels, including beta-sterols, monounsaturated fatty acids, and a statin. Avoid using red yeast rice together with other herbal/health supplements that can harm your liver, such androstenedione, chaparral, comfrey, DHEA, germander, kava, niacin, pennyroyal oil, and others. Grapefruit may interact with red yeast rice and lead to unwanted side effects. A 2017 study found that levels of monacolin K in red yeast rice supplements sold in the U.S. ranged from undetectable to nearly 11 milligrams per daily recommended dose, which is … While red yeast rice can significantly reduce high levels of LDL ("bad") cholesterol, a recently published analysis of 28 brands re-emphasized the fact that amounts of active, cholesterol-lowering compounds can range from none to potent levels, yet this information is not found on labels. What Is Red Yeast Rice? RYR is a rice product made by fermenting rice with the mold Monascus purpureus.