Casey Johnson Autopsy: Diabetes, Possible NyQuil Overuse, No Illegal Drugs

Per complete autopsy report, heiress had a "history of possible excess use" of the nighttime cold medicine

Sadly, it's too late for Casey Johnson to take better care of herself.

Diabetic ketoacidosis, a condition that results when too much acid builds up in the body, was the official cause of death, according to the complete report obtained Thursday by E! News.

And, per the report, Johnson's condition was "poorly controlled due to noncompliance with medications."

That and she had a "history of possible excess use of NyQuil."

But at least the 30-year-old mother of an adopted daughter was not testing her body's limitations by abusing the hard stuff.

"Toxicology tests were negative for drugs of abuse," the report states.

However, in addition to hypothyroidism, insomnia and depression, she had a history of substance abuse, according to the coroner's findings.

Insulin, Motrin, the sedative clonazepam, and other over-the-counter medications were the only foreign substances found in Johnson's system at the time of her death.

Johnson was found dead in her Los Angeles home on the morning of Jan. 4. She had just gotten engaged to the overemotive Tila Tequila a month beforehand.

—Reporting by Whitney English