Been taking 2500mg tylenol (acetaminophen) daily 1 month now due to chronic jaw pain. Under dr care. Can this cause overdose or poisoning? Safe to continue? How long?

Borderline Safe. The max dose of tylenol (acetaminophen) is about 3000 mg per day. It can be very toxic to your liver. If you are not sensitive or allergic to Ibuprofen or naprosin [non-steroidal anti inflammatories], the dosage of tylenol (acetaminophen) could be reduced and the others substituted for your pain control. If your pain is in part from inflammation the the non-steroidal medicines will help. Tell your dr about the concerns.
Maximum Tylenol (acetaminophen) Dose. The current maximum daily dose of Acetaminophen (tylenol) is 4000mg, divided into 1000mg doses, every 6-hours. This maximal dosage should only be continued for 7-days. All the above is predicated on the adult patient having a healthy liver, and no other medical or pharmacological contraindications. Moreover, what is the underlying cause? That is the most important question that needs answered.