My younger daughter has a medical alert - she has Crohn's, Ankylosing Spondylitis, and Gastroparesis on there. We're going to change it to add in "GJ tube."
She is on MANY medications and so those are online and just a phone call away if there is an emergency. She also has low bone density and a blood condition which are online. I think all of this important info for her doctors/EMTs to know, especially if something goes wrong.
Her older sister just has AS and is just on a few meds (four) so we didn't think she needed medic alert. She does have a card in her wallet with all her medical info.
I think the need for a medic alert depends on many things - the conditions you have, the meds you are on etc.