Medicare Glossary

Observation Status

A classification used when a hospital monitors your condition before deciding whether to formally admit you. Even if you stay overnight, observation status is considered outpatient care (Part B), not inpatient (Part A). This distinction matters for skilled nursing facility eligibility.

Also known as: Outpatient observation

Open Enrollment Period (OEP)

For Medicare Advantage, the period from January 1–March 31 each year when enrolled MA beneficiaries can switch to a different MA plan or return to Original Medicare (with Part D if desired). Changes take effect the first of the following month.

Also known as: OEP, Medicare Advantage OEP

Original Medicare

The traditional fee-for-service Medicare program offered directly through the federal government, consisting of Part A (hospital insurance) and Part B (medical insurance). Under Original Medicare, you can go to any doctor or hospital that accepts Medicare.

Also known as: Traditional Medicare, Fee-for-service Medicare

Out-of-Network

Providers, facilities, or suppliers that do not have a contract with your health plan. Using out-of-network providers often costs more. Some Medicare Advantage plans (like PPOs) allow out-of-network use at higher cost; others (like HMOs) generally do not.

Out-of-Pocket Maximum

The most you will have to pay for covered services in a plan year. After you reach this limit, your plan pays 100% of covered costs. Medicare Advantage plans must have an out-of-pocket maximum; Original Medicare does not have one.

Also known as: Out-of-pocket limit, MOOP