How many tylenols (acetaminophen) can i take at once for a bad headache?

It depends: Make sure you take tylenol (acetaminophen) or Acetaminophen only as directed by the package. Generally, you can take up to 1000 mg at a time if you do not have a history of liver disease or are taking medications that interact with or contain Acetaminophen (check the ingredient list on the box--it's present in alot of other medications). No one should not take more than 4000 mg in a 24 hour period.

TWO: The max recommended adult dose for tylenol (acetaminophen) is 1000mg every 6 hours for no more than 4000mg a day. Anything more than this will not likely give added pain relief but will increase risk of toxicity, and tylenol (acetaminophen) overdose can be very serious.