EXCLUSIVE

Charles Manson was supposed to have surgery Thursday night for intestinal bleeding, but doctors determined he was too weak and the procedure too risky ... TMZ has learned.

Sources familiar with the situation tell us ... Manson was taken from Corcoran State Prison to a Bakersfield hospital a few days ago because of a lesion in his intestines that was causing significant bleeding.

We're told doctors wanted to perform surgery shortly after the 82-year-old arrived at the hospital but he refused.

Our sources say Thursday Manson had a change of heart and agreed to the surgery, but during pre-op late yesterday doctors determined he needed to go under the knife ... but felt it was life-threatening because his condition was too weak.