[header] How to determine your primary health insurance as a dependent on both plans [title] Determine whether the rule covers your situation. [step] The " birthday rule " is used to determine which health insurance plan is primary if you are a dependent on both plans, but it only applies to children. [substeps] If you are a minor, you can use the birthday rule to determine your primary health insurance plan. 
The rule also may apply if you are over the age of 18, but you're a college student and still considered a dependent of your parents. [title] Find out the birthdays of your parents.