Is this Kaiser? It happens automatically when they are 15. Which is perfect because I take them to all their appointments, I pay for the medicine they are prescribed - and I have no access to the accounts so I don't get the reminders.
It's a completely insane system and we missed a bunch of appointments until I realized what had happened when they turned 15. Now I control all the accounts - logging in to 4 separate accounts to make appointments for each of the children.