What is a co-insurance?

Co-insurance is a provision in a health or dental insurance plan where you and the insurance company  share, in a specific ratio, the covered expenses under a policy after meeting the deductible.  For example, the insurer may reimburse the insured for 80 percent of covered expenses, the insured paying the remaining 20 percent of such expenses.  (e.g., 20% paid by you and 80% paid by the plan).