Frequently asked questions How much cannabis can I possess in Texas with an MMJ Prescription? Those who qualify for medical marijuana in Texas can only purchase cannabis products that are no more than 0.5% THC (tetrahydrocannabinol) and no less than 10% CBD (cannabidiol) from a licensed dispensary. Cannabis flower and marijuana-infused edibles are not available to legally purchase in Texas. Depending on the amount of marijuana and type (type of product, whether or not it’s a high THC variety) you’re caught with, you could be facing life imprisonment over simple possession in Texas. There are no defined possession limits for medical marijuana patients in Texas.