How health insurance works
Understand your insurance. Know what you're paying for. Know what to do next.
Health insurance can feel complicated. This guide breaks down premiums, deductibles, copays, coinsurance, networks, claims, and EOBs in plain English.
This guide focuses on health insurance in the United States. Your specific plan may have different rules.
Start with the basics ↓What actually happens when you use your insurance?
Every visit to a doctor follows roughly the same path. Once you can see the whole path, your paperwork makes a lot more sense.
You receive care
A visit, procedure, test, or prescription.
Provider submits a claim
Sent to your insurer on your behalf.
Insurer processes the claim
Checked against your plan's rules.
Insurance pays its share
Based on your specific benefits.
You receive an EOB
An explanation — not a bill.
You may receive a bill
For any remaining balance.
The important part
Having insurance doesn't mean you pay nothing.
Insurance generally shares healthcare costs with you, according to your plan's specific rules.
The five numbers that shape what you pay
Insurance paperwork keeps returning to the same five terms. Once these make sense, most of what you read afterward will too.
Premium
What you pay to keep your coverage active.
Keeps coverage in force — doesn't mean care is free.
Deductible
What you may pay before your plan begins paying, according to its rules.
Not every service is subject to it.
Copay
A fixed amount you may pay for a covered service.
Predictable, but varies by service type.
Coinsurance
A percentage of the cost you may pay, generally after your deductible is met.
Scales with the price of the service — a copay doesn't.
Out-of-pocket max
The most you generally pay for covered services subject to the plan's limit.
Premiums generally don't count toward it.
You may pay more of the allowed cost yourself.
Your plan may begin sharing costs through copays or coinsurance.
Your plan generally pays 100% of covered services for the rest of the plan year.
Your actual cost also depends on the service itself, whether it's covered, and whether the provider is in-network.
"Covered" doesn't always mean free
The service is eligible for benefits under your plan.
Deductible, copay, and coinsurance may still apply to a fully covered service.
In-network vs. out-of-network
Network status is one of the biggest factors in what you'll pay. Always check the rules of your specific plan.
In-network
Uses your plan's negotiated rates
- Participates in your plan's network
- Usually lower patient costs
- Uses negotiated, contracted rates
Out-of-network
No contract with your plan
- May cost more
- May have different coverage rules
- May use a separate deductible or out-of-pocket limit
- You could be billed for the difference between the charge and what insurance paid
Claim, EOB, bill — what's the difference?
Three different documents, from two different senders, meaning three different things.
Provider → Insurance
A request for payment
Submitted to your insurer by your provider.
Insurance → You
An explanation, not a bill
Shows how the insurer processed the claim.
Provider → You
A request for payment
Asks you to pay the amount you owe.
Remember this one rule
An EOB is generally NOT a bill.
Don't send payment to your insurer from an EOB — your provider sends a separate bill for anything you owe.
Why didn't insurance pay everything?
The specific reason for your situation should be reflected in your EOB, denial notice, or other insurance correspondence.
When insurance doesn't pay the way you expected
My claim was denied
Understand the reason for the denial before deciding what to do next.
Understand my denial →I received an unexpected bill
Compare your bill with your EOB and identify what you may actually owe.
Understand my bill →Your path to resolution
Every guide on The Patient Insider follows this same path — including everything linked from this page.
What is happening?
What applies to you?
What's your best move?
What do you need to do?
Take action.
Move it toward resolution.
What are you dealing with right now?
Guides marked "Coming soon" are being built next.
I received an EOB
Read my Explanation of Benefits
Read the guide →My insurance claim was denied
Understand my denial
Read the guide →I want to fight a denial
Overturn a claim denial
Read the guide →I'm ready to appeal
Open the Appeal Builder
Start the tool →I want a checklist first
Free Insurance Appeal Checklist
Get the checklist →I received a medical bill
Understand my bill
Read the guide →I don't understand my billing codes
Medical billing codes explained
Read the guide →What to check before receiving care
- Is my provider in-network?
- Is the service covered?
- Does it require prior authorization?
- Have I met my deductible?
- What copay or coinsurance might apply?
- Is the facility in-network?
- Does my plan have special rules?
- Should I call my insurer first?
A starting point, not a guarantee — confirm details with your insurer.
Common questions about how insurance works
Does paying my premium mean my care is free?
No. Your premium keeps your coverage active. You may still owe money through your deductible, copay, or coinsurance, up to your plan's out-of-pocket maximum.
What's the difference between a claim and a bill?
A claim is what your provider submits to your insurer to request payment. A bill is what your provider sends you directly for any amount you owe.
Why does the same service cost different amounts?
Each provider may have a different negotiated rate with your insurer, or none at all if out-of-network. In-network providers typically cost less.
What happens if I go out-of-network?
Your plan may pay less or nothing, or you could be billed the difference between the charge and what your insurer paid. Rules vary by plan type.
Do I need prior authorization for every service?
No — typically only for specific services your plan identifies. Check your plan documents or call your insurer before scheduling anything unfamiliar.
Don't just understand your insurance.
Know what to do next.
The Patient Insider helps you move from confusion to a clear next step.