Coinsurance /wp-content/uploads/glossary_videos/Co_Insurance.mp4 Coinsurance is the percentage of the bill you owe when you go to the doctor. The amount I owe when I visit my doctor is determined by the coinsurance rate. A 10% coinsurance rate means I owe 10% of the cost. Related Articles: Kicking Off a Gap Year with a World Record and an Angel Investor