If Medicare is your only form of health insurance, Medicare is always primary.
If you have coverage through an employer group health insurance plan Medicare can be primary or secondary. If the employer has 20 or more employees, the plan is primary. If fewer than 20 employees, Medicare is primary.
If you have coverage through an employer group health insurance plan Medicare can be primary or secondary. If the employer has 20 or more employees, the plan is primary. If fewer than 20 employees, Medicare is primary.