coinsurance

noun

co·​in·​sur·​ance ˌkō-ən-ˈshu̇r-ən(t)s 

also -ˈin-ˌshu̇r-

1

: joint assumption of risk (as by two underwriters) with another

2

: insurance (such as fire insurance) in which the insured is obligated to maintain coverage on a risk at a stipulated percentage of its total value or in the event of loss suffer a penalty in proportion to the deficiency

3

: health insurance in which the insured is required to pay a fixed percentage of the cost of medical expenses after the deductible has been paid and the insurer pays the remaining expenses

Coinsurance is not a new idea—Americans who grew up in the era before managed care will remember their parents paying 20% of the costs of office visits, tests, and prescriptions.

—Thomas H. Lee et al.

Examples of coinsurance in a Sentence

Recent Examples on the Web

In some cases, patients would be billed coinsurance and other payments related to the unnecessary equipment, the complaint says. —Sarah Volpenhein, jsonline.com, 6 Mar. 2026

In the best-case scenario (their premium, copay, coinsurance for two hospital days, their deductible), their cost will be nearly $14,000. —Dr. Rahul K. Parikh, Mercury News, 2 Mar. 2026

For insured patients who have to pay coinsurance — a certain percentage of the list price — when buying prescription drugs, or for those in high-deductible plans who need to pay list prices before meeting deductibles, the move will bring down out-of-pocket costs. —Elaine Chen, STAT, 24 Feb. 2026

Meanwhile, Millar said other people have 25% to 33% of their coinsurance linked to the list prices of those drugs. —Annika Kim Constantino, CNBC, 24 Feb. 2026

Word History

First Known Use

circa 1889, in the meaning defined at sense 1

Rhymes for coinsurance

• concurrence
• deterrence
• incurrence
• occurrence
• recurrence
• transference
• countertransference

Medical Definition

coinsurance

noun

co·​in·​sur·​ance ˌkō-ən-ˈshu̇r-ən(t)s, -ˈshər- also -ˈin-ˌshu̇r-, -ˌshər- 

: health insurance in which an insurer requires the insured to pay a fixed percentage of the cost of medical expenses after the deductible has been paid and with the insurer to pay the remaining expenses

Coinsurance is not a new idea—Americans who grew up in the era before managed care will remember their parents paying 20% of the costs of office visits, tests, and prescriptions.

—Thomas H. Lee et al., The New England Journal of Medicine

Legal Definition

coinsurance

noun

co·​in·​sur·​ance ˌkō-in-ˈshu̇r-əns, kō-ˈin-ˌshu̇r- 

1

: joint assumption of risk (as by two underwriters) with another

2

: insurance (as fire insurance) in which the insured is obligated to maintain coverage on a risk at a stipulated percentage of its total value or in the event of loss to suffer a penalty in proportion to the deficiency