Health insurance underwriting is how an insurer evaluates risk to decide whether to cover you and what to charge. For plans sold on the individual and small group markets under the Affordable Care Act, that process has been stripped down to four allowed factors, and no one can be turned away for being sick. Outside those markets (short-term policies, health sharing ministries, and Medigap purchased after its open window) traditional medical underwriting is still very much alive, and your health history can mean higher premiums, excluded conditions, or an outright denial.
The Four Factors an ACA Plan Can Price On
Federal law limits an insurer pricing an individual or small group health plan to exactly four variables: whether the plan covers one person or a family, the geographic rating area, the applicant’s age, and tobacco use.1Office of the Law Revision Counsel. 42 USC 300gg – Fair Health Insurance Premiums Nothing else enters the formula. Not your weight. Not your prescription list. Not a cancer diagnosis last spring.
Age pricing is capped at a 3-to-1 ratio for adults, so the most an insurer can charge a 64-year-old is three times what it charges a 21-year-old for the same plan.1Office of the Law Revision Counsel. 42 USC 300gg – Fair Health Insurance Premiums Geographic rating areas reflect local provider costs, hospital prices, and how many carriers compete in the region. A plan in a rural county served by one hospital system often costs more than the same plan in a metro area with several networks fighting for members.
Tobacco use can push a premium up by as much as 50 percent compared with non-users.1Office of the Law Revision Counsel. 42 USC 300gg – Fair Health Insurance Premiums The sting is sharper than it looks because premium tax credits generally do not offset the tobacco portion. Roughly a dozen states and the District of Columbia have restricted or eliminated the surcharge, so where you live changes what the law lets your insurer do.
Guaranteed Issue, Community Rating, and Genetic Protections
Before the ACA, insurers routinely combed through medical records, pharmacy histories, and prior claims to decide whom to cover and at what price. That ended for ACA-compliant plans. Federal law now requires every insurer selling individual or group coverage to accept every applicant in the state who applies.2GovInfo. 42 USC 300gg-1 – Guaranteed Availability of Coverage Health status cannot be used to turn you down, and an insurer cannot invoke a preexisting condition to exclude benefits or deny a policy.3Office of the Law Revision Counsel. 42 USC 300gg-3 – Prohibition of Preexisting Condition Exclusions
Community rating reinforces the protection. Rather than pricing you around your personal health profile, insurers price everyone in the same area and age band at essentially the same base rate. Someone managing diabetes pays what someone with no chronic conditions pays, assuming identical age, location, family size, and tobacco status. The cost of care spreads across the community instead of landing on the sickest people alone.
Genetic information has its own federal shield. Under the Genetic Information Nondiscrimination Act, health insurers cannot use genetic test results, family medical history, or participation in genetic research when making coverage or pricing decisions, and they cannot require you or your family to take a genetic test as a condition of coverage.4National Human Genome Research Institute. Genetic Discrimination
When You Can Actually Enroll
Guaranteed issue is not the same as sign-up-any-day coverage. ACA marketplace plans are sold during an annual open enrollment period, typically running from November through mid-January for coverage the following year. Outside that window you need a qualifying life event to open a special enrollment period. Common ones include losing existing coverage (including aging off a parent’s plan at 26), getting married or divorced, having or adopting a child, and moving to a new ZIP code or county.5HealthCare.gov. Qualifying Life Event (QLE) Gaining citizenship, leaving incarceration, and certain income changes that affect subsidy eligibility also count.
Miss both windows and you cannot buy an ACA-compliant plan until the next enrollment period. Some people in that gap turn to short-term plans or health sharing ministries, which do underwrite medically and can refuse you or carve out conditions. A handful of states also impose financial penalties for going uninsured.
Employer Group Plans
Group health plans use a different model. The insurer evaluates the workforce as a unit, looking at average employee age, industry, group size, and the group’s past claims experience. That collective assessment sets the total premium the employer pays. A construction company with an older workforce and higher injury rates sees different group pricing than a tech startup staffed by twenty-somethings.
What matters to you as an employee is that group-level risk cannot be translated into individual-level pricing. Federal regulations prohibit a group health plan from requiring any individual employee to pay a higher premium based on a health factor, including health status, medical history, claims experience, genetic information, or disability.6eCFR. 29 CFR 2590.702 – Prohibiting Discrimination Against Participants and Beneficiaries Based on a Health Factor Your coworker with a chronic illness pays the same employee contribution you do for the same tier. These plans are generally governed by the Employee Retirement Income Security Act, which sets federal minimum standards for employer-sponsored health benefits.7U.S. Department of Labor. ERISA
Wellness programs can bolt extra incentives onto that framework. Federal rules cap wellness incentives at 30 percent of the total cost of coverage for general health-related programs and 50 percent for programs aimed at reducing tobacco use.8eCFR. 45 CFR 146.121 – Prohibiting Discrimination Against Participants and Beneficiaries Based on a Health Factor A “wellness discount” that requires hitting a biometric target (a specific BMI or cholesterol number) functions as a health-based premium variation even though it is technically voluntary, and these programs must offer a reasonable alternative for people who cannot meet the standard because of a medical condition.
Lasering in Self-Insured Plans
Large employers often self-insure, paying claims directly out of company funds instead of buying a fully insured policy. To cap their exposure, they buy stop-loss insurance that kicks in once claims cross a set threshold called the attachment point. This is where individual-level underwriting quietly returns, through a practice called lasering.
When a stop-loss insurer spots a high-cost employee (someone with cancer, organ transplant needs, or another expensive condition), it can assign a higher attachment point just to that person or exclude them from stop-loss coverage entirely. The employee’s own benefits do not change, but the employer carries more financial risk for that person’s care before the stop-loss policy pays anything. For a small self-insured employer, one lasered employee can be a serious budget problem. It is one of the few corners of employer health coverage where an individual’s health profile still has a direct financial consequence, even if the worker never sees it on a pay stub.
Plans That Still Use Medical Underwriting
Several categories of coverage sit outside the ACA’s guaranteed issue and community rating rules. In those plans, your health answers still drive the decision.
Short-Term Limited-Duration Insurance
Short-term plans are designed as temporary gap coverage and are explicitly exempt from ACA consumer protections. Insurers can deny applicants based on health status, exclude preexisting conditions, impose annual and lifetime benefit limits, and skip essential health benefits like mental health or maternity care.9Centers for Medicare & Medicaid Services. Short-Term, Limited-Duration Insurance Fact Sheet Applicants typically fill out detailed health questionnaires, and insurers may run prescription database checks to see what medications have been filled.10National Association of Insurance Commissioners. Short-Term Limited-Duration Health Plans
A 2024 federal rule limited short-term plans to an initial term of three months, with total coverage including any renewal capped at four months.11Federal Register. Short-Term, Limited-Duration Insurance and Independent, Noncoordinated Excepted Benefits Coverage Federal duration limits have shifted across administrations, and several states impose their own caps or ban short-term plans altogether. Check your state’s current rules before buying.
Health Sharing Ministries and Excepted Benefits
Health sharing ministries are not insurance in the legal sense and are not regulated as insurance. They can require full medical disclosure, deny participation based on health history, and exclude costs related to preexisting conditions. Members share medical costs through a pooling arrangement, but no contract guarantees that any particular bill will be paid.
Excepted benefits, which include standalone dental and vision plans, also fall outside ACA underwriting requirements. Federal law defines them as limited-scope benefits typically offered separately from a comprehensive medical plan.12Office of the Law Revision Counsel. 42 USC 300gg-91 – Definitions Because they are exempt from guaranteed issue and community rating, insurers offering standalone dental or vision coverage may use health-based underwriting, impose waiting periods for certain procedures, or limit benefits for preexisting conditions.
Medigap and the Six-Month Window
Medigap policies cover gaps in Original Medicare such as copayments and deductibles, and the underwriting rules are nothing like the ACA marketplace. Timing is everything.
Federal law gives you a one-time, six-month Medigap open enrollment period that starts the first month you are both 65 or older and enrolled in Medicare Part B.13Office of the Law Revision Counsel. 42 USC 1395ss – Certification of Medicare Supplemental Health Insurance During those six months no insurer can deny you a Medigap policy, use medical underwriting, or charge more because of preexisting conditions.14Medicare. Get Ready to Buy You can enroll in any standardized Medigap plan sold in your state at the same price as anyone else your age.
Once the window closes, that protection largely disappears. Insurers can run full medical underwriting, charge higher premiums based on your health, or deny the application entirely.14Medicare. Get Ready to Buy A few qualifying events (losing employer group coverage, disenrolling from a Medicare Advantage plan within the first year, or having your plan commit fraud or terminate) trigger a narrow federal guaranteed issue right. Those rights apply only to specific Medigap plan letters and are far more limited than the open enrollment protections. Some states expand them.
This is where people get hurt. Someone turning 65 who delays Part B because they still have employer coverage is fine; the Medigap clock starts when they do enroll in Part B. But someone who enrolls in Part B at 65, skips Medigap, and tries to buy a policy five years later may be priced out or denied. The six-month window does not come back.
Rescission for Fraud
Guaranteed issue leaves insurers one real tool: rescinding a policy if you committed fraud or intentionally misrepresented something material on the application. Federal law bars rescission in nearly every other circumstance, and the insurer must give you prior notice before canceling.15Justia Law. 42 USC 300gg-12 – Prohibition on Rescissions
For ACA-compliant plans, this provision has a narrow practical reach. Insurers cannot use your health history to set premiums or deny coverage up front, so there is less incentive to lie on an application. The real rescission risk sits with plans that still underwrite: short-term coverage and Medigap bought outside open enrollment. If you fail to disclose a condition the insurer specifically asked about and it later surfaces, the insurer can cancel the policy retroactively. You could be left uninsured and responsible for claims the insurer already paid. Honest answers on any health insurance application are the cheapest protection you can give yourself.