A deductible is the amount of money that a policyholder must pay out of pocket before their insurance company will begin to cover medical expenses. Insurance companies are only liable to pay claims that exceed the deductible amount. Having a deductible or co-pay in a health insurance plan prevents unnecessary claims and treatments by requiring the insured to pay a portion of costs. High deductible plans have lower premiums but provide no benefit if medical costs do not surpass the deductible minimum. The appropriate insurance plan depends on individual factors like medical history and health conditions.