'King of Infomercials' Don Lapre -- Self-Mutilation Suspected in Apparent Suicide

Officials found a "large amount of blood" in the jail cell where "King of Infomercials" Don Lapre was discovered Sunday morning, law enforcement sources tell TMZ ... and we're told it appears Don had cut himself.

As we previously reported, Don was set to appear in court on Tuesday to face 41 counts of conspiracy and fraud ... for allegedly selling a bogus product called The Greatest Vitamin in the World.

Don's body was discovered in his Arizona jail cell early Sunday morning -- officials believe he committed suicide.