Curtis Collman III had 180 times the lethal limit of methamphetamine in his blood stream, a toxicology report revealed, according to the Seymore Tribune.
His father, Curtis Collman II, has been charged with neglect which led to the death of his son, and possession of meth.
The 41-year-old told police his son woke up early on 21 June and said he was hungry, but Collman told him there was no food in the house in Seymour, WDRB reports.
However, there was meth left on a plate, which police said could have been mistaken for cereal as the apartment had no lighting.
After his son fell ill, Collman called a female friend over who told him to take his son to hospital.
But Collman allegedly ripped her phone out of her hand and told her he didn't want to return to prison, before leaving the room and returning with a handgun, pointing it at her and saying he could kill all three of them.
Collman then drove his son to his parents' house instead of hospital, where he became “stiff” and began turning blue, leading his grandfather to call 911.
The boy was taken to hospital but later died. He had taken 18,000 nanograms of meth, which has a lethal dose of around 100 nanograms.
Collman faces up to 40 years in prison if he is found guilty of causing death by neglect.
He also faces charges of pointing a firearm, theft and failure to register as a sex offender, WAVE 3 News reported.
He will go on trial on 4 December.