Possible side effects of red yeast rice include headaches, heartburn, upset stomach, elevation of liver and muscle enzymes, and muscle and liver problems, according to WebMD. Some types of red yeast rice may contain high levels of other potentially dangerous substances, such as citrinic acid, claims WebMD.
There are safety concerns regarding products containing red yeast rice that are marketed as dietary supplements in the United States. Such products may contain a potentially-harmful contaminant or may cause identical side effects as certain cholesterol-lowering drugs, such as lovastatin, according to the National Center for Complementary and Integrative Health.
While further research on the long-term safety of red yeast rice is needed, as of 2015, experts believe that the known risks of lovastatin – including elevation of liver and muscle enzymes and liver and muscle problems – logically apply to red yeast rice, as stated by WebMD.
There are reports of individuals taking red yeast rice who suffered side effects including myopathy, rhabdomyolysis and liver toxicity, according to the NCCIH. In a 2011 study, four of the 11 products of red yeast rice contained the contaminant citrinin, which caused genetic damage in human cells and kidney failure in animals during studies of the contaminant, as reported by the NCCIH.