If you don’t know what Medical ID is, it’s time to learn.
First, open the Health app on your iPhone. Next, tap “Medical ID” on the bottom right. You’ll be able to fill out medical conditions, add notes about allergies and reactions and enter in emergency contacts like your significant other or parents. There’s even a section where you can say whether or not you’re an organ donor.
More importantly, you should know to look for this in case you ever see someone in distress. Grab their iPhone, swipe on the home screen, tap emergency, and you’ll see what sort of information is in their Medical ID.