Can you be on two health insurance plans?

Yes, one will pay primary and one will pay secondary. Secondary: a policy that pays the provider's leftover medical bills. Some might still exclude the payment toward bills assigned to meet the primary policy's deductibles or copayments so you have to ask. This happens for instance if a husband or wife covers their spouse on their insurance but he/she also participates in their employer's plan. The spouse's coverage would pay the bills after their own medical plan paid.