Health insurance jargon confuses almost everyone. Understanding how health insurance works helps you pick the right plan, avoid surprise bills and use benefits you are already paying for. This guide focuses on the US system, with notes for the UK, Canada and Nigeria.
The key terms
| Term | What it means |
|---|---|
| Premium | What you pay every month to have coverage |
| Deductible | What you pay for covered care before the plan starts sharing costs |
| Copay | A fixed amount for a visit or prescription |
| Coinsurance | Your percentage of costs after the deductible, such as 20% |
| Out-of-pocket maximum | The most you pay in a year for covered in-network care |
| Network | Doctors and hospitals with agreed prices with your insurer |
An example of how health insurance works
Your plan has a $2,000 deductible, 20% coinsurance and a $6,000 out-of-pocket maximum. You need a $10,000 procedure:
- You pay the first $2,000 (deductible).
- For the remaining $8,000, you pay 20%, which is $1,600.
- Your total is $3,600. The insurer pays $6,400.
If you had more bills that year, your costs would stop at $6,000, plus premiums.
Types of plans
- HMO: lower costs, usually requires a primary care doctor and referrals.
- PPO: more flexibility to see specialists and out-of-network providers, usually higher premiums.
- High-deductible health plan: lower premiums, higher deductible, and may qualify you for an HSA.
How to choose a plan
- Estimate how much care you usually use.
- Add up the yearly premium plus likely out-of-pocket costs.
- Check that your doctors and prescriptions are covered.
- Make sure you could afford the deductible from your emergency fund.
Budget for coverage with our Insurance Cost Estimator.
Young adult tips
- In the US, you can often stay on a parent’s plan until age 26.
- Marketplace plans may come with subsidies based on income.
- Preventive care such as check-ups and many vaccines is often covered at no cost.
- Always check whether a provider is in-network before non-emergency care.
Outside the US
UK residents use the NHS, with some paying for private insurance for faster access. Canadians have provincial public coverage, often topped up with workplace plans for dental, vision and drugs. In Nigeria, options include the National Health Insurance Authority schemes, employer plans and private HMOs; check what each plan covers and which hospitals accept it.
Questions to ask before choosing a plan
Understanding how health insurance works is easier when you ask the right questions during enrollment:
- Are my current doctors and nearby hospitals in-network?
- Are my regular prescriptions covered, and at what cost?
- What is the deductible, and could I pay it from savings?
- What is the out-of-pocket maximum?
- Does the plan cover mental health, dental or vision?
- Is the plan HSA-eligible?
Write down your answers for each plan and compare the total expected yearly cost. The cheapest premium is not always the cheapest plan if you use care regularly. Estimate your full insurance budget with our Insurance Cost Estimator.
For official, up-to-date guidance, see HealthCare.gov.
Frequently asked questions
Do I pay the deductible before my insurance pays anything?
For many services, yes, though preventive care and some copay services may be covered before you meet the deductible.
What is the difference between a copay and coinsurance?
A copay is a fixed amount; coinsurance is a percentage of the cost.
Is a high-deductible plan a good idea?
It can suit healthy people with an emergency fund, especially when paired with an HSA.
How health insurance works: key takeaways
- Premiums keep coverage active; deductibles come first when you use care.
- Coinsurance and copays share costs after that.
- The out-of-pocket maximum caps your yearly costs.
- Compare total yearly cost, not just the premium.
Last reviewed: October 2026. This article is general education, not personal financial, tax or legal advice. Rules, rates and limits change, so check official sources or speak to a qualified professional before making decisions. See our Financial Disclaimer.