Initial Posting: 2/13/2018    Last Update: 2/13/2018
Answer: CoQ10 supplements are generally well-tolerated, even when taken in relatively high doses. Rarely, gastrointestinal symptoms such as nausea and diarrhea have been reported, as has mild insomnia. Piperine, which is sometimes added to CoQ10 supplements to increase bioavailability, may also cause side effects, and may interact with certain medications. For more details, plus how to minimize the occurrence of CoQ10 side effects, see the Concerns and Cautions section of the CoQ10 and Ubiquinol Supplements Review.