...to be able to differentiate which drug PT and PTT are used for that I have found helpful: When you write ptt the two letter Ts form an H, H is for Heparin. Soo.. if you remember ptt is for heparin then pt belongs to warfarin... I know this doesn't explain the difference between the two but hopefully it can help someone remember which one goes with which drug.. Before someone gave me this trick I couldn't remember which one went with which drug for the world.. Now it is a piece of cake... yum...