If you are under the influence of alcohol, but your blood alcohol level is lower than 0.08, you can be charged with a general impairment DUI under 75 Pa. C.S. § 3802(a)(1).
If your blood alcohol level is between 0.08% and 0.10%, you can be charged with driving under the influence of alcohol under 75 Pa. C.S. § 3802(a)(2).
When the blood alcohol level is over 0.10% but lower than 0.16%, the driver can be charged with driving under the influence of a high rate of alcohol.
If your blood alcohol level is 0.016 % or higher, you can be charged with driving under the influence of alcohol at the highest tier.
If you have any traceable amount of a Schedule I controlled substance or its metabolite in your system, you can be charged with DUI
If you have a Schedule II or III controlled substance in your system and you don't have a prescription for it, you can be charged with driving under the influence
You can be charged with DUI even if you are using a prescription or other drug or combination of drugs if aren't capable of operating a vehicle safely
Pennsylvania law also prohibits driving under the influence of an inhalant or "whippit"