Kill something (Moschops and Phiomia are good because they provide a lot of meat) before shooting it, then lead the Dimetrodon to the corpse as you tranq it. Around halfway through the process or when its low on health stand near the corpse and let the Dimetrodon attack you. It will consume the corpse as it attacks you, and regain health. This way there will be no risk of killing it. You can also use a Snow Owl to heal it if you have one.