Medicare does cover pre-existing conditions, treating them the same way as new medical conditions.
If Medicare covers a pre-existing condition that is medically necessary, then Parts A and B of Original MedicareOriginal Medicare is a fee-for-service health insurance program available to Americans aged 65 and older and some individuals with disabilities. Original Medicare is provided by the federal government and is made up of two parts: Part A (hospital insurance) and Part B (medical insurance). will cover it.
Having Parts A and B allows you to add supplemental coverage in the form of MedigapMedicare Supplement Insurance (Medigap) is designed to provide coverage that Original Medicare (Parts A and B) does not. Medigap policies are purchased in addition to Original Medicare and have their own monthly premiums you'll need to pay., which doesn’t always cover pre-existing conditions.
In the world of health insurance, a “pre-existing condition” is exactly what it sounds like: It’s a medical condition that exists before you begin health insurance coverage.
Simply put, when it comes to Medicare, your pre-existing conditions are covered.
That being said, there is one Medicare-related offering — Medigap supplemental insurance — where pre-existing conditions may be subject to a waiting period.
When it comes to Medicare and pre-existing conditions, you don’t have to worry.
Most U.S. citizens first become eligible to enroll in Medicare for their health insurance needs at age 65. By that stage in life, you likely have been treated for more than one medical condition over your lifetime.
The good news is that when you sign up for Part A and/or Part B of Original Medicare, any pre-existing conditions will be covered immediately, the same way Medicare would cover any new medical concerns.
That’s also the case with Medicare Advantage plans, which private insurance companies provide under the guidance of the Medicare program. These plans feature at least the same coverages as Part A and Part B of Original Medicare. 
How does Medicare handle pre-existing conditions?
Medicare handles pre-existing conditions the same way it addresses new concerns. If Medicare offers coverage of a given condition and the treatment is medically necessary and is performed by a Medicare-approved medical professional at a Medicare-approved facility, then Medicare will cover the condition — whether it’s an old one or a new one.
Does Medicare B cover pre-existing conditions?
Both Part A of Original Medicare and Part B of Original Medicare cover pre-existing conditions.
Part A of Original Medicare covers inpatient surgeries and medically necessary stays after you meet the benefit period deductible. Under Part A, you don’t have to pay daily coinsurance after the deductible until Day 61 of your stay.
Part B of Original Medicare covers outpatient surgeries and things like doctor visits and medically necessary equipment. After you pay your annual deductible, Part B covers 80% of the cost while you pay the other 20% in the form of coinsurance.
Medicare has covered pre-existing conditions since its inception in 1965.
That once was a unique distinction, but that changed in 2014 when the Affordable Care Act took effect and closed the gap. Outside of some grandfathered individual health insurance plans, insurance companies can no longer deny coverage or increase rates because of a pre-existing condition. 
While that’s true with health insurance policies, it’s not true for all health insurance-related products — including one that can impact Medicare beneficiaries.
Most of the time, Medigap plans cover pre-existing conditions — if you add one in time.
For many people who choose Original Medicare (Parts A and B) for their healthcare coverage, Medigap plans are crucial to the financial puzzle, filling in the gaps of covered costs like deductibles, coinsurance and copays.
While those who switch to Medicare Advantage plans enjoy the protection of an annual out-of-pocket maximum, Original Medicare doesn’t have an out-of-pocket maximum that puts a hard cap on your financial responsibilities.
Those with both Parts A and B of Original Medicare can add a Medigap plan from private insurance companies. All 10 of the standard Medigap plans cover 100% of Part A coinsurance and at least 50% of Part B coinsurance and copayment. Two Medigap plans also feature an out-of-pocket maximum.
If you add a Medigap policy during your Medigap Open Enrollment Period — which spans the first six months in which you are 65 or older and are first enrolled in Part B — then your eligibility and your rates can’t be impacted by a pre-existing condition (Note: You could still face up to a six-month waiting period for your pre-existing conditions to be covered, but not if you had creditable coverage for at least six months leading up to signing up for Medigap). 
If, however, you decide to add a Medigap policy after your Medigap Open Enrollment Period, you may face a waiting period, may have to pay more, or may even be denied coverage altogether because of a pre-existing condition.
How does Medicare know if I have pre-existing conditions?
If you wait until after your Medigap Open Enrollment period, your application is subject to medical underwriting. That means you will be asked questions about your current health, including pre-existing conditions, and that analysis can impact how much you have to pay for Medigap or if you even qualify at all.
What pre-existing conditions are not covered?
There isn’t a pre-existing conditions list per se, but obviously the more expensive the treatment of your condition(s) tends to be, the more difficult time you may have getting an affordable policy after your Medigap Initial Enrollment Period.
Does Medicare have a coverage waiting period for pre-existing conditions?
Medicare doesn’t, but Medigap may.
Your Medigap plan could be subject to a waiting period of up to six months before your pre-existing condition(s) would be covered. Even so, there’s good news:
- Medigap can’t impose a waiting period for a pre-existing condition if you had other creditable health insurance for six months before enrolling. If you had coverage for less than six months, you might face a shorter waiting period (up to five months if you had coverage for one month, up to four months if you had coverage for two months and so on).
- Even if you have a Medigap waiting period for a pre-existing condition, Parts A and B would still cover the pre-existing condition as usual (and you must have Parts A and B to get Medigap).
In addition, if you have a “guaranteed issue right,” then an insurance company must sell you a Medigap policy and can’t impose a waiting period or charge more because of pre-existing conditions. Medicare.gov lists several scenarios where a guaranteed issue right applies. 
While it’s pretty straightforward that Medicare will cover pre-existing conditions, the situation isn’t always as clear-cut if you decide to add a Medigap policy to Parts A and B. A GoHealth licensed insurance agent, without obligation, can help you navigate those waters and figure out what the right fit is for your specific situation.