They don't. But if they see WARFARIN on a bracelet they immediately know that the patient is not likely to stop bleeding if they are bleeding, and if there is internal bleeding they need to move FAST.
Similarly if they see TYPE 1 DIABETES on a bracelet they immediately know that the patient requires insulin to metabolise sugars amongst other things.
They are very useful if you have a medical condition which means that you will need different treatment from other people, and flag up a problem before you have even reached the hospital or someone has looked up your record.
