Final answer:
An EMS provider must check the expiration date of nitroglycerin before assisting patients in taking it.
Step-by-step explanation:
Before assisting patients in taking their own nitroglycerin, an EMS provider must check the expiration date of the medication. This is important because nitroglycerin is a medication that loses its effectiveness over time. If the medication is expired, it may not provide the intended benefits and could potentially be harmful.