Having two health insurance can help you pay for the medical treatments you need. However, it does not mean that they work at the same time; one is classified as the primary insurer, and the other one stays as a secondary insurer. The former is your principal coverage and is the first to pay for medical bills; while the latter pays the remainder that the primary did not pay (part or even the full bill). This means that both health insurances cannot pay more than 100% of the medical costs you received.