: You may take 4,000 milligrams daily up to 10 days for pain. Taking more puts you at risk for liver failure. "We see unintentional overdoses when people combine multiple products with acetaminophen, such as Nyquil and Tylenol," says Dr. Jan Engle, past president, American Pharmacists Association. If you're taking it long-term for chronic pain, consider having liver function tests done once or twice a year.