In short
Premium, deductible, copay, coinsurance, out-of-pocket maximum, network, EOB and prior authorization, with one example.
US health insurance uses many special words. Learn these once and every plan becomes easier to read.
Premium: the fixed amount you pay every month to have the plan, even if you never see a doctor. At a job, it is usually taken from your paycheck.
Deductible: what you pay yourself each year before the plan starts paying for most care. Example: a $2,000 deductible means you pay the first $2,000 of covered care.
Copay: a fixed fee for a service, for example $30 for a doctor visit or $10 for a medicine.
Coinsurance: your percentage of the cost after the deductible. With 20% coinsurance, you pay $20 of every $100.
Out-of-pocket maximum: the most you pay in one plan year for covered, in-network care. After you reach it, the plan pays 100% for the rest of the year. Your premiums do not count toward it.
Your plan has a $1,500 deductible, 20% coinsurance and a $6,000 out-of-pocket maximum. You have a $10,000 hospital bill.
You pay the first $1,500 (the deductible).
On the remaining $8,500 you pay 20%: $1,700.
Your total is $3,200. The plan pays $6,800.
If you have more care later that year, you never pay more than $6,000 in total.
Network: the doctors, hospitals and labs that have a contract with your plan. In-network care costs much less. Out-of-network care can cost much more, or not be covered at all.
Plan year: often January to December. For school plans it is often August to August.
Preventive care: check-ups, many screenings and recommended vaccines. Most plans cover these at $0 when you use an in-network doctor.
Prior authorization: the plan must approve some care before you get it, for example an MRI or an expensive medicine. Your doctor's office usually asks for it. If you skip it, the plan may refuse to pay.
Referral: a written OK from your main doctor to see a specialist. Some plans require it.
Formulary (drug list): the medicines your plan covers, grouped in price levels called tiers.
EOB (Explanation of Benefits): a letter or app message from your insurer after each visit. It shows what the doctor charged, what the plan paid and what you may owe. It says "This is not a bill." Wait for the real bill from the doctor or hospital, then compare the two.
Keep a photo of both sides on your phone. It shows your member ID, group number, copays, and phone numbers, often including a 24-hour nurse line.
Choosing the lowest premium without looking at the deductible. A cheap plan can cost more if you get sick.
Paying a bill before the EOB arrives. Check that the plan was billed first.
Assuming a hospital in your network means every doctor there is in your network. Ask.