Why This Glossary Matters
Health insurance documents are dense by design — they define obligations, limits, and costs using terminology that can feel like a second language. Misreading a single term, like confusing your deductible with your out-of-pocket maximum, can result in unexpected bills. This glossary defines the core vocabulary you'll actually encounter when reviewing, selecting, or using a health insurance plan in the United States.
For a broader orientation to how US health coverage works, see our plain-language overview of health insurance. If you're also reviewing other policy types, our life insurance glossary and auto insurance glossary follow the same format.
This article is general educational information, not personalized insurance, legal, or financial advice. Coverage terms, costs, and rules vary significantly by plan and state. Always read your actual policy documents and consult a licensed insurance agent or adviser for guidance specific to your situation.
| Plan Year | Typically January 1 – December 31 for most marketplace plans (Healthcare.gov) |
| ACA Out-of-Pocket Maximum (individual, 2024) | $9,450 for individual coverage (CMS, 2024) |
| HSA Contribution Limit (individual, 2024) | $4,150 (IRS, 2024) |
| Open Enrollment Period (Marketplace) | Typically November 1 – January 15 (Healthcare.gov) |
| Metal Tier Options | Bronze, Silver, Gold, Platinum (ACA marketplace structure) |
Core Cost Terms: What You Pay and When
Most confusion about health insurance bills traces back to five cost-sharing terms. Understanding how they interact is the foundation of reading any plan clearly.
Premium
The fixed monthly amount you pay to maintain health insurance coverage, regardless of whether you use any medical services that month. Employer-sponsored plans often split this cost between the employer and employee.
Deductible
The amount you must pay out of pocket for covered health services each plan year before your insurer begins sharing costs. A $2,000 deductible means you pay the first $2,000 in covered claims yourself.
Copayment (Copay)
A fixed dollar amount you pay for a specific covered service, such as $30 for a primary care visit. Copays often apply even before your deductible is met, depending on your plan.
Coinsurance
Your percentage share of covered medical costs after you've met your deductible. If your coinsurance is 20%, you pay 20% of a covered bill and your insurer pays the remaining 80%.
Out-of-Pocket Maximum
The most you will pay for covered services in a plan year, including deductibles, copays, and coinsurance. Once this cap is reached, your insurer covers 100% of covered costs for the rest of the year.
Formulary
The official list of prescription drugs covered by your health plan, typically organized into tiers that determine your cost-sharing. Drugs not on the formulary are generally not covered or require an exception process.
EOB (Explanation of Benefits)
A statement from your insurer — not a bill — that summarizes what was billed for a service, what the insurer paid, and what you owe. Reviewing EOBs helps you catch billing errors.
Open Enrollment
The annual period during which you can enroll in, change, or drop health coverage. Outside of this window, changes are generally only permitted if you qualify for a Special Enrollment Period due to a qualifying life event.
HSA (Health Savings Account)
A tax-advantaged savings account available to those enrolled in a qualifying High-Deductible Health Plan (HDHP). Funds can be used for eligible medical expenses and roll over year to year, unlike an FSA.
FSA (Flexible Spending Account)
An employer-sponsored account allowing pre-tax contributions for qualified medical expenses. Unlike an HSA, most FSA funds must be used within the plan year or are forfeited.
Coordination of Benefits
The process used when a person is covered by more than one health plan to determine which insurer pays first (primary) and which pays second (secondary), preventing duplicate payments.
Subrogation
The right of an insurer to seek reimbursement from a third party (or that party's insurer) after paying a claim caused by that third party — for example, recovering costs after an accident caused by another driver.
Here's a practical example: Suppose your deductible is $1,500, your coinsurance is 20%, and your out-of-pocket maximum is $6,000. After you pay the first $1,500 in covered costs, your insurer covers 80% of subsequent bills. Once your total out-of-pocket spending reaches $6,000 in a plan year, the insurer covers 100% of covered costs for the remainder of that year.
Deductibles and Copays Don't Always Interact
Some plans apply copays for common services like office visits and prescription drugs even before you meet your deductible, while others require the deductible to be met first. Reading your Summary of Benefits and Coverage (SBC) document carefully will clarify exactly how your specific plan sequences these costs. When in doubt, call the member services number on your insurance card.
Plan Structure and Network Terms
Your plan's structure determines which providers you can see, how referrals work, and what you'll pay for going outside a defined network.
- HMO (Health Maintenance Organization): Requires you to choose a primary care physician (PCP) who coordinates your care and provides referrals to specialists. Generally lower premiums but less flexibility in provider choice.
- PPO (Preferred Provider Organization): Allows you to see any provider, in-network or out-of-network, without a referral. Out-of-network care costs more but is still partially covered.
- EPO (Exclusive Provider Organization): Like an HMO in that it limits you to a specific network, but typically does not require a PCP or referrals. Out-of-network care is generally not covered except in emergencies.
- HDHP (High-Deductible Health Plan): Features higher deductibles and lower premiums, and is the only plan type compatible with a Health Savings Account (HSA).
- In-Network vs. Out-of-Network: In-network providers have a contracted rate with your insurer, reducing your costs. Out-of-network providers have no such agreement, meaning higher — sometimes much higher — cost-sharing for you.
- Prior Authorization: A requirement that your insurer approve certain procedures, medications, or referrals before you receive them. Skipping this step can result in claim denial.
Checking whether your current doctors and preferred hospitals are in-network before enrolling in a plan is one of the most consequential steps in the selection process. Personal finance decisions like plan selection connect directly to overall budget management — see our personal finance terminology guide for context on how insurance costs fit into a broader financial picture.
49%
Americans with employer-sponsored health insurance
According to KFF's 2023 Employer Health Benefits Survey, roughly half of Americans receive coverage through an employer.
$1,763
Average annual employee premium contribution (single coverage)
KFF Employer Health Benefits Survey, 2023, for single coverage employer-sponsored plans.
28%
Adults who report difficulty understanding health plan terms
Research published in Health Affairs suggests a significant share of insured adults struggle to correctly apply common insurance concepts like deductibles and coinsurance.
The content on this site is for informational purposes only and is not a substitute for professional advice. Always consult a qualified professional for guidance specific to your situation.