How Health Insurance Works: Premiums, Deductibles, and Coverage

What Is Health Insurance?

Health insurance is a contract between a policyholder and an insurance company (or government program) in which the insurer agrees to pay a portion of medical expenses in exchange for regular premium payments. Health insurance reduces the financial risk of unexpected medical costs, which can be catastrophic without coverage. In the United States, health insurance is obtained through employers, government programs (Medicare, Medicaid, CHIP), or individual marketplace plans established under the Affordable Care Act (ACA).

The U.S. healthcare system is notably complex, with multiple plan types, cost-sharing mechanisms, and provider networks. Understanding key terms is essential to making informed decisions about coverage and controlling out-of-pocket spending.

Core Cost-Sharing Terms

Health insurance involves several cost-sharing mechanisms that determine what the insurer pays vs. what the patient pays:

Term	Definition	Example
Premium	Monthly amount paid to maintain coverage, regardless of whether care is used	$400/month for an individual plan
Deductible	Amount paid out-of-pocket before insurance begins paying (except preventive care)	$1,500 deductible: patient pays first $1,500 of eligible costs each year
Copay	Fixed amount paid per visit or service, regardless of total cost	$30 copay for a primary care visit
Coinsurance	Percentage of costs shared between patient and insurer after deductible is met	80/20 coinsurance: insurer pays 80%, patient pays 20%
Out-of-pocket maximum	The most a patient pays in a plan year; after this, insurer covers 100%	$7,000 out-of-pocket max: once reached, all covered costs are paid by insurer
Network	Group of doctors, hospitals, and facilities contracted with the insurer at negotiated rates	In-network providers cost less than out-of-network providers

How a Claim Flows

To illustrate how these components interact, consider a patient with a $1,500 deductible, 80/20 coinsurance, and $7,000 out-of-pocket maximum who receives a $10,000 surgery:

Patient pays the first $1,500 (deductible) entirely
Remaining $8,500 is subject to coinsurance: patient pays 20% = $1,700; insurer pays 80% = $6,800
Patient's total cost: $1,500 + $1,700 = $3,200
If the patient's total out-of-pocket hits $7,000 during the year, all subsequent covered costs are paid by the insurer at 100%

Plan Types: HMO, PPO, EPO, and HDHP

Health insurance plans differ in how they structure access to providers and manage costs:

Plan Type	Provider Network	Primary Care Referral	Out-of-Network Coverage	Typical Cost
HMO (Health Maintenance Organization)	Restricted to network	Required for specialists	Generally none (emergencies excepted)	Lowest premiums
PPO (Preferred Provider Organization)	In-network preferred; out-of-network allowed	Not required	Yes, at higher cost	Higher premiums
EPO (Exclusive Provider Organization)	Restricted to network	Not required	Generally none (emergencies excepted)	Moderate premiums
HDHP (High-Deductible Health Plan)	Varies; often PPO-style	Varies	Varies	Low premiums; high deductible ($1,600+ individual in 2024)
POS (Point of Service)	Network-based with out-of-network option	Required	Yes, at higher cost	Moderate

HMO Plans

Health Maintenance Organizations require members to choose a primary care physician (PCP) who coordinates all care and provides referrals to specialists. Care must stay within the network. HMOs typically have the lowest premiums and simplest claims processes, but offer the least flexibility.

PPO Plans

Preferred Provider Organizations offer the most flexibility. Members can see any provider — in-network or out-of-network — without a referral, though in-network care is significantly cheaper. PPOs are popular with patients who have existing specialist relationships or chronic conditions requiring specialized care.

High-Deductible Health Plans (HDHPs) and HSAs

HDHPs feature lower premiums but higher deductibles ($1,600+ for individuals in 2024 per IRS rules). They are paired with Health Savings Accounts (HSAs) — tax-advantaged accounts that allow participants to save pre-tax dollars for qualified medical expenses. HSA contributions reduce taxable income, grow tax-free, and can be withdrawn tax-free for medical costs. Unlike Flexible Spending Accounts (FSAs), HSA funds roll over year to year, making them a powerful long-term savings vehicle.

What Health Insurance Typically Covers

Under the ACA, all marketplace plans must cover ten categories of essential health benefits:

Ambulatory patient services (outpatient care)
Emergency services
Hospitalization (inpatient care)
Maternity and newborn care
Mental health and substance use disorder services
Prescription drugs
Rehabilitative and habilitative services and devices
Laboratory services
Preventive and wellness services (at no cost to the patient)
Pediatric services, including dental and vision for children

The Formulary: Prescription Drug Coverage

Insurance plans organize covered medications into a formulary — a tiered list of drugs. Lower tiers (generic drugs) have the lowest copays; higher tiers (brand-name or specialty drugs) require higher cost-sharing. Checking whether specific medications are on a plan's formulary is critical for patients who take regular prescriptions.

Key Considerations When Choosing a Plan

Total cost, not just premium: A low-premium HDHP may cost more overall if you use significant care due to the high deductible. Calculate expected total costs (premiums + likely out-of-pocket) based on your health needs.
Provider networks: Verify that your preferred doctors and hospitals are in-network before enrolling.
Prescription drug coverage: Check the formulary for your current medications.
Out-of-pocket maximum: This is your financial safety net; lower is better for people with serious health conditions.
HSA eligibility: If enrolled in an HDHP, maximizing HSA contributions offers triple tax advantages.

Health insurance is one of the most consequential financial decisions individuals and families make annually. Understanding how cost-sharing mechanisms interact, and matching plan type to actual healthcare usage patterns, can save thousands of dollars per year.

This article is for informational purposes only and does not constitute financial advice.