This is a good point.
I'm diabetic have been for 5 years now.
Most of people I ride with regularly know this.
Why is this important? Cause if I'm stumbling around they won't think I'm drunk, they will know to get me to my bike.
Because it's even more important to carry the proper stuff with you. I have a tubing of icing in the saddlebag to get me up,and a couple of granola bars to keep me there.
Also a couple of days worth of meds in case a trip goes longer then expected.
Now mine is totally undercontrol so it really isn't an issue.
But the other reason to tell your friends is in the case of a wreck or you going to the hospital out of sorts, you might not be able to tell the medics yourself.
