http://www.medications.com/effect/view/28286 Relative with lung cancer was given Omeprazole 20 mg. once a day. On the second day, he started coughing up huge amounts of red blood which continued for hours and lessening throughout the day. That evening he questioned if the new prescription could have Mon, 24 Mar 2008 01:07:57 -0400 http://www.medications.com/effect/view/28286?item=5770 Yes my online search also did not reveal bleeding as one of the side effect, but better consider your physician immediately. As far I know chest pain is one of the serious side effect. There are few other serious side effects you can look at them at http:/ http://www.medications.com/effect/view/28286?item=5770