The report was released Thursday by police.
Shannon Herrin Huddleston, 38, apparently put on an overcoat before entering the freezer in her garage on Aug. 8, authorities said. She died from the "toxic effects of methamphetamine," with hypothermia a contributing factor.
The autopsy report noted fresh puncture wounds on her body, and toxicology tests found meth, marijuana, hydrocodone and an unspecified anti-anxiety medication, the Fort-Worth Star-Telegram reported Friday.
Her son, 19, found her body, face-up in the freezer, when he went to get food, a search warrant stated.
Her death was ruled an accident by police.