How Much Cannabis Do You Need To Treat Epilepsy? Home › Forums › How Much Cannabis Do You Need To Treat Epilepsy? This topic has 0 replies, 1 voice, and was last updated 6 years, 3 months ago by HempHappy. Viewing 1 post (of 1 total) Author Posts March 5, 2019 at 11:23 pm #1965 HempHappyMember From 5-20 milligrams or more are used to treat epilepsy, which varies from person to person. Author Posts Viewing 1 post (of 1 total) You must be logged in to reply to this topic. Log In Username: Password: Keep me signed in Log In