A pre-existing condition (PEC) is a health problem, such as diabetes, cancer, or high blood pressure, that you had before the date your new health coverage starts. Historically, insurance companies could deny coverage or charge significantly higher premiums based on a person’s medical history. However, federal law now ensures that Medicare must cover treatment for pre-existing conditions. If you are eligible for Medicare, your existing health issues generally do not prevent you from enrolling or increase your premium for the core coverage.
Coverage Under Original Medicare (Parts A and B)
Original Medicare (Parts A and B) covers all medically necessary services for pre-existing conditions immediately upon coverage starting. Eligibility for Medicare, typically based on age or disability, is the only prerequisite, not your current health status or medical diagnoses. The program treats pre-existing conditions the same way it treats new medical issues, with no waiting period.
Part A covers inpatient care, such as hospital stays, skilled nursing facility care, and hospice care. This coverage starts providing benefits right away for any condition requiring an inpatient admission.
Part B covers outpatient services and supplies, including doctor visits, lab tests, and durable medical equipment needed to manage chronic illnesses. All necessary physician visits, supplies for diabetes, or chemotherapy are covered without delay. Beneficiaries are still responsible for the standard deductibles, copayments, and coinsurance amounts that apply under Original Medicare.
Rules for Medicare Advantage Plans (Part C)
Medicare Advantage Plans (Part C) are offered by private insurance companies that contract with Medicare to provide Part A and Part B benefits. These plans are legally required to accept individuals with pre-existing conditions. An Advantage plan cannot refuse enrollment, increase the monthly premium, or deny coverage for medically necessary treatment simply due to a chronic illness.
This protection extends to nearly all health conditions. Historically, individuals with End-Stage Renal Disease (ESRD) were restricted from enrolling, but a federal rule change in 2021 now allows all Medicare-eligible people with ESRD to enroll.
Once enrolled, you receive all the benefits of Original Medicare, plus often additional benefits like prescription drug coverage. The plan cannot impose a waiting period for coverage of any pre-existing condition, ensuring continuous care from the moment the plan becomes effective.
The Medigap Exception: Enrollment and Waiting Periods
While Original Medicare and Medicare Advantage cover pre-existing conditions immediately, Medicare Supplement Insurance (Medigap) policies have a unique exception concerning out-of-pocket costs. Medigap plans are sold by private companies to help cover the deductibles, copayments, and coinsurance left by Original Medicare. These plans are subject to medical underwriting outside of specific enrollment windows.
The most secure time to enroll is during your six-month Medigap Open Enrollment Period (OEP). This period begins the month you turn 65 and are enrolled in Medicare Part B. During the OEP, you have a guaranteed issue right, meaning insurers must sell you any plan without medical underwriting. They cannot deny coverage, charge a higher premium based on health status, or impose a waiting period for pre-existing conditions.
If you apply for a Medigap policy outside of your OEP or a guaranteed issue right situation, the insurance company can use medical underwriting. This allows them to ask about your health history and potentially deny you a policy if you have a significant pre-existing condition.
If accepted outside a guaranteed issue period, the insurer may impose a pre-existing condition waiting period of up to six months. During this time, the Medigap policy will not cover out-of-pocket costs for a condition treated or diagnosed within six months before the policy started. If you had at least six months of continuous “creditable coverage” before applying, this waiting period must be waived or reduced.
Ensuring Seamless Coverage and Avoiding Penalties
Timely enrollment in Medicare ensures seamless coverage and helps avoid financial penalties. The Initial Enrollment Period (IEP) for Medicare Part B is seven months long, beginning three months before your 65th birthday, including your birth month, and ending three months after. Enrolling during this period prevents long-term cost increases.
If you fail to enroll in Part B when first eligible and lack other qualifying coverage, you must wait for the General Enrollment Period (GEP) from January 1 to March 31. Coverage will not start until July 1. This delay results in a Part B late enrollment penalty, which is a permanent 10% increase to the monthly premium for every full 12-month period you were eligible but not enrolled.
Delaying enrollment in a Medicare Part D prescription drug plan can also result in a permanent late enrollment penalty. This occurs if you go 63 or more days without creditable drug coverage. The penalty is added to your monthly Part D premium for as long as you have the coverage, emphasizing the need for prompt action during initial eligibility windows.