<s>[INST] my husband was rushed to the hospital with blood in his urine  cat scan showed no kidney stone  today he was rushed back with suvere back pain which he was given pain med for and seemed to pass   he was told it may have been a blood clote  that passed through again cat scan showed no kidney stone.  my question what if any are the interactions between red yeast rice he has been on for 2 yrs with  wararin sod 4 mg which he was just put on for afib [/INST] Hi! Welcome to Chat Doctor! Red yeast rice is made by fermenting a type of yeast called Monarchs purposes over red rice and used both as a food and medicine. Since, your husband has been consuming red yeast rice for the last 2 years, and recently he was started on Warfarin 4 mg for his atrial fibrillation. The persistent bleeding that occurred is due to the interaction between the red yeast rice and warfarin. Red yeast rice is known to increase the bleeding in patients who are receiving warfarin. Your husband must undergo the following lab tests PT and INR then he must consult his doctor to see the change in the dose or use of other Chat Doctor. Regards! </s>