Jason David says medical marijuana is the only thing that's helped get the boy's rare form of epilepsy under control. He says it doesn't contain THC, the chemical which produces a high.
It's kept in the fridge, then heated to a liquid when it is time to take it.
The six year old suffered violent seizures and was taking so many medications, he showed withdrawal symptoms.
David is convinced the pot has saved his son's life. He says a doctor suggested he try marijuana to treat him.
"It was really a life or death situation," David said. "If I were you I would try anything to save your son's life. When you see your kid suffer every single day... my son had a seizure every single day for four-and-a-half-years. I'm getting my son back from being a zombie to becoming a human again."
Modesto police say medical marijuana use is legal, based on a doctor's orders. They say when an adult gives a child pot without a prescription, it's time to investigate.