Complete Insurance Glossary: 50+ Terms Every Patient Should Know

If you have stared at an insurance document and felt completely lost, this glossary is for you. These are the terms insurers use when processing and denying your claims — defined in plain language, with enough context to be useful when you are dealing with a real dispute. Knowing this vocabulary gives you a significant advantage when filing an appeal.

Why This Glossary Matters for Appeals

Insurance companies speak their own language, and the gap between what they say and what patients understand is not accidental. When an insurer denies your claim citing "adverse benefit determination" or "non-quantitative treatment limitation," they are counting on you not knowing what those terms mean. This glossary closes that gap.

A

Adverse Benefit Determination The official term for a denial, rescission, or reduction of a covered benefit. When your insurer says no to a claim, Prior Authorization Denied: How to Appeal" class="auto-link">prior authorization request, or appeal, it is an "adverse benefit determination." This term triggers your legal right to appeal under ERISA (29 U.S.C. § 1133) and the ACA.

Allowed Amount The maximum amount your insurer will pay for a specific service — also called the eligible expense, payment allowance, or negotiated rate. For in-network providers, it is the contracted rate. For out-of-network providers, it is often set much lower, leaving you with a large balance bill.

Appeal A formal request to your insurance company (or an independent reviewer) to reconsider a denied claim or adverse benefit determination. There are two types: internal appeals (reviewed by the insurer) and external appeals (reviewed by independent reviewers). The ACA (45 C.F.R. § 147.136) guarantees the right to both.

Authorization (Prior Authorization / Prior Auth) Pre-approval from your insurer before you receive certain medical services or medications. Without it, your claim may be denied even if the treatment is medically appropriate. Also called "pre-certification" or "pre-authorization."

B

Balance Billing When an out-of-network provider charges you the difference between their full fee and what your insurer paid. The No Surprises Act (42 U.S.C. § 300gg-111) prohibits balance billing for emergency services and certain non-emergency services at in-network facilities.

Benefit A covered medical service, supply, or drug that your insurance plan will pay for (in whole or in part) under the plan's terms.

Birthday Rule The rule used to determine which parent's health plan is primary for a child covered by both parents' plans. The parent whose birthday falls earlier in the calendar year has the primary plan — regardless of which parent is older.

C

Claim A formal request submitted to an insurer by a provider or patient for payment of medical services already rendered.

Clinical Criteria The medical standards and guidelines insurers use to determine medical necessity. Insurers often use proprietary products like InterQual or MCG (Milliman Care Guidelines). Under ERISA § 1133, you are entitled to receive the specific criteria used to deny your claim.

Coinsurance Your share of costs for a covered service, expressed as a percentage. If your coinsurance is 20% and the allowed amount is $1,000, you pay $200 after your deductible is met.

Copay (Copayment) A fixed dollar amount you pay for a covered service, regardless of the total cost.

Coordination of Benefits (COB) The process that determines which insurer pays first (primary) and which pays second (secondary) when you are covered by more than one health plan.

Contractual Adjustment The difference between a provider's billed amount and the allowed amount under the insurer's contract. This amount is written off — neither you nor your insurer pays it.

Coverage Determination A decision by your insurer about whether a specific drug or service is covered under your plan. For Medicare Part D, a coverage determination is the first formal step in the drug appeals process.

D

Deductible The amount you pay for covered services before your insurance begins to share costs. Resets at the beginning of each plan year.

Denial See Adverse Benefit Determination. A refusal by your insurer to pay a claim or authorize a service. Denials must be provided in writing with specific reasons and instructions for appealing under ERISA and the ACA.

Durable Medical Equipment (DME) Medical equipment for home use — wheelchairs, walkers, CPAP machines, hospital beds. Covered in most plans but often requires prior authorization.

E

EOB (Explanation of Benefits) A document sent by your insurer after a claim is processed. It explains what was billed, what the insurer paid, what was adjusted, and what you owe. An EOB is not a bill.

Essential Health Benefits (EHBs) Ten categories of services ACA-compliant plans must cover under 42 U.S.C. § 18022: ambulatory services, emergency services, hospitalization, maternity and newborn care, mental health and substance use disorder treatment, prescription drugs, rehabilitative services, laboratory services, preventive care, and pediatric services.

External Independent Review: Complete Guide" class="auto-link">External Review An independent review of an insurer's adverse benefit determination by an organization not affiliated with the insurer. Under the ACA, you have the right to external review for most coverage disputes involving medical judgment. External reviewers overturn insurer decisions roughly 40% of the time.

ERISA (Employee Retirement Income Security Act) The federal law governing most employer-sponsored health benefit plans. ERISA defines your appeal rights and requires a "full and fair review" of all benefit claim denials under 29 U.S.C. § 1133.

F

Formulary Your insurer's list of covered prescription drugs, organized into cost-sharing tiers. Non-formulary drugs may not be covered unless you obtain a formulary exception.

Formulary Exception A request to have a non-formulary drug covered, or a formulary drug covered at a lower tier. Requires documentation from your doctor that the formulary alternative is inappropriate.

G

Grandfathered Plan A health plan that existed before March 23, 2010 and has not made significant changes. Grandfathered plans are exempt from some ACA requirements, including certain preventive care mandates and external review rights.

Grievance A formal complaint about a non-clinical matter — such as customer service, billing errors, or plan administration. Distinguished from an appeal, which challenges a coverage or medical necessity decision.

H

HIPAA (Health Insurance Portability and Accountability Act) A federal law that protects the privacy of your medical information and ensures you can maintain health insurance when you change jobs. HIPAA also gives you the right to access your own medical records.

HMO (Health Maintenance Organization) A plan type that requires you to use in-network providers and get referrals from a primary care physician to see specialists.

I

In-Network Providers who have contracts with your insurer to provide services at negotiated rates.

InterQual A widely-used proprietary clinical criteria product (owned by Change Healthcare/McKesson) that insurers use to evaluate medical necessity for inpatient stays, procedures, and certain treatments. If your denial cites "InterQual criteria not met," request the specific criteria under ERISA § 1133.

L

Lien (Health Insurance Lien) A claim your health insurer places on money you receive from a third-party personal injury settlement, to recover medical expenses it paid on your behalf. Also the mechanism behind subrogation.

Lifetime Maximum / Lifetime Limit The maximum dollar amount an insurer will pay over your lifetime. The ACA prohibits lifetime limits on essential health benefits for ACA-compliant plans under 42 U.S.C. § 300gg-11.

M

MCG (Milliman Care Guidelines) A proprietary clinical criteria product widely used by insurers and utilization review organizations to evaluate medical necessity. Specific criteria can be requested when a denial cites MCG.

Medical Necessity The standard insurers use to determine whether a treatment is appropriate, required, and covered. Insurers' definitions of medical necessity often favor cost-effectiveness over clinical optimization.

Mental Health Parity The requirement under MHPAEA (29 U.S.C. § 1185a) that health plans apply the same coverage standards to mental health and substance use disorder benefits as to comparable medical/surgical benefits.

N

Network Adequacy The regulatory standard requiring insurance networks to have enough providers to give members reasonable access to care without unreasonable delay or travel. If your plan has no in-network provider for a needed specialty, you may qualify for a network adequacy exception.

No Surprises Act Federal law effective January 1, 2022 (42 U.S.C. § 300gg-111) prohibiting balance billing for emergency services, non-emergency services at in-network facilities from out-of-network providers, and certain air ambulance services.

NQTL (Non-Quantitative Treatment Limitation) A coverage restriction that limits the scope or duration of benefits for treatment in ways that are not expressed numerically — such as prior authorization requirements, step therapy, or fail-first policies. Under 2024 MHPAEA regulations, insurers must provide written NQTL parity analyses showing mental health and medical/surgical benefits are treated comparably.

O

Out-of-Network Providers who do not have contracts with your insurer. Out-of-network care typically costs more.

Out-of-Pocket Maximum (OOP Max) The most you will pay for covered services in a plan year. After reaching the OOP max, your insurer pays 100% of covered services.

P

Plan Year The 12-month period during which your health plan benefits apply. Deductibles and OOP maximums reset at the start of each plan year.

PPO (Preferred Provider Organization) A plan type that covers both in-network and out-of-network care, with higher cost-sharing for out-of-network. No PCP referral required.

Prior Authorization See Authorization. The requirement to obtain insurer approval before receiving certain services or medications.

R

Rescission The retroactive cancellation of your insurance coverage. The ACA (45 C.F.R. § 147.128) prohibits rescissions except in cases of fraud or intentional misrepresentation.

S

Step Therapy (Fail-First) A protocol requiring patients to try and fail on one or more cheaper treatments before an insurer will cover the prescribed treatment. Over 30 states have enacted step therapy override laws.

Subrogation Your insurer's right to seek reimbursement from a third party — or from your settlement proceeds — when that third party is responsible for your medical expenses.

Summary of Benefits and Coverage (SBC) A standardized document summarizing your plan's benefits, costs, and coverage limitations. The ACA requires insurers to provide an SBC to all enrollees.

Summary Plan Description (SPD) For ERISA plans, the SPD comprehensively describes your plan's benefits, eligibility, and appeal procedures. You are entitled to a free copy at any time under ERISA § 1024.

U

Utilization Review (UR) The process insurers use to evaluate whether medical care is appropriate and necessary. UR occurs prospectively (prior auth), concurrently (continued stay review), and retrospectively (post-service review).

UCR (Usual, Customary, and Reasonable) A methodology some insurers use to set out-of-network allowed amounts. UCR determinations have been criticized as systematically undervaluing services and leaving patients with large balance bills.

Fight Back With ClaimBack

Knowing the vocabulary is the first step. Now you can speak the insurer's language, identify the legal grounds for your denial, and build a compelling appeal. ClaimBack turns this knowledge into action — generating a professional, evidence-based appeal letter in 3 minutes. Start your free claim analysis → Free analysis · No credit card required · Takes 3 minutes

Related Reading

• How to Write an Insurance Appeal Letter
• What Is Medical Necessity?
• Internal vs External Insurance Appeal