When does medical insurance stop for a child insured by the non custodial parent's coverage if the child is 18 but a full time college student?

Where do you live? Laws vary, but in general, any insurance provision should be outlined in the original custody/support order. Oregon mandates that support and items such as health insurance be continued until the child is 21 if he/she is unmarried and enrolled in school at least half time. Other states have provisions allowing for extension of support/insurance for children up to a certain age if they remain in school. Other states have no such provision and support ends along with all other expenses including health insurance, when the child reaches the age of majority or emancipation as outlined by their state's laws.

The custodial parent may have the option to file a motion to extend health care coverage for the child enrolled in college, but again that depends on where you live whether or not this would be allowed and/or granted.