What is an HMO?

Health Maintenance Organization (HMO): A health plan that is also involved in how your health care is delivered.  HMOs generally allow members to have lower out-of-pocket healthcare expenses but may offer less choice and flexibility in the choice of doctors or hospitals than other plans. If you're a member of an HMO, you will be required to pick a primary care physician (PCP). Your PCP will take care of your healthcare needs. Before you can see a specialist, your PCP will need to give you a referral for a visit.

If you have an HMO, you're likely to have coverage for a broader range of preventive healthcare examinations than would be available with another plan type. You may have to pay a deductible prior to coverage and you may also have to pay a co-payment before doctor visits. With an HMO plan, you're not likely to have to submit any of your personal claims to the insurance organizations. But remember that you are likely to have no coverage for services rendered by providers outside of the network or for services provided without an official referral from your PCP. 

A Medicare HMO: An HMO that has contracted with the federal government under the Medicare Advantage program (formerly called Medicare+ Choice) to provide health benefits to persons eligible for Medicare that choose to enroll in the HMO, instead of receiving their benefits and care through the traditional fee for service Medicare program.

For More information:

California Department of Managed Healthcare:  What is an HMO?