Frequently asked questions How much cannabis can I possess in Ohio with an MMJ Card? In Ohio, patients and caregivers can possess the following amounts with a valid MMJ Card: – up to a 90-day supply of medical marijuana, to be determined by the physician. Per state law, a patient who purchases a 30-day supply from their first dispensary trip would be limited to no more than a 60-day supply of medical marijuana until 90 days after the initial purchase. Smoking is not an approved method of delivery. However, medical patients can buy oils, tinctures, plant material and patches.