According to Newhealthguide.org, it is safe to take Tylenol and Advil together. The appropriate course of action for mixing these pain killers is to start by taking two Advil (assuming 200 mg tablets). If there is still pain after 2-3 hours, a person can take two Tylenol (325 mg tablets).
Though they are typically considered to be relatively safe, over the counter medicines, great care should still be taken when taking Tylenol and Advil. The recommended dosage on the bottles should be strictly followed for both pain killers. According to Harvard Medical School, Tylenol can cause liver damage when the dosage limits are exceeded, and Advil can increase the risk of a heart attack in the user.