Medicare covers a wide range of medical services, from hospital stays and doctor visits to preventive screenings and prescription drugs, but it has significant gaps that catch many people off guard. The most commonly cited exclusions are routine dental care, vision exams, and hearing aids, though the list of things Medicare will not pay for extends well beyond those three categories. Understanding what falls inside and outside coverage can save you thousands of dollars and prevent unpleasant surprises at the worst possible time.
The Basic Structure of Coverage
Medicare is divided into parts, and each part covers a different category of care. Part A handles inpatient hospital stays, skilled nursing facility care, hospice, and some home health services. Part B covers outpatient care, doctor visits, lab tests, durable medical equipment, and preventive services. Part D covers prescription drugs through private insurance plans that contract with Medicare. Medicare Advantage, sometimes called Part C, bundles Parts A and B (and usually D) into a single plan run by a private insurer, often adding extras like limited dental or vision coverage in exchange for network restrictions and other rules.
Most people pay no monthly premium for Part A if they or a spouse paid Medicare taxes for at least ten years. Part B carries a monthly premium that rises with income. Part D premiums vary by plan. These premiums, along with deductibles, copays, and coinsurance, mean that “covered” does not mean “free.” Even for services Medicare does pay for, your share of the bill can be substantial.
Hospital Stays and the Observation Status Problem
Part A covers inpatient hospital stays, including a semi-private room, meals, nursing care, medications administered during the stay, and other hospital services. After you meet an annual deductible, Part A picks up the full cost for the first 60 days, then charges daily coinsurance amounts that increase as the stay extends. Stays beyond 90 days in a benefit period draw on a limited reserve of “lifetime reserve days,” and once those are gone, you pay the entire bill.
One of the most consequential traps in hospital coverage involves something called observation status. Even if you spend two or three nights in a hospital bed receiving treatment, the hospital may classify you as an outpatient under “observation” rather than formally admitting you as an inpatient. This distinction matters enormously. Under observation status, your care is billed through Part B rather than Part A, which typically means higher copays for each service and medication. Research comparing observation stays with formal inpatient admissions found that observation patients had a higher rate of unplanned returns to the hospital within 30 days, roughly four percentage points higher than inpatient admissions.1PubMed Central. Association of Observation Stays with Clinical Outcomes and Costs in Medicare: An Instrumental Variable Analysis
The observation status classification also creates a downstream problem with skilled nursing care, which is covered next.
Skilled Nursing Facility Care and the Three-Day Rule
Medicare Part A covers care in a skilled nursing facility after a hospital stay, but only if you were formally admitted as an inpatient for at least three consecutive days. Observation days do not count toward that three-day requirement. So if you spent two nights admitted and one night under observation, Medicare considers your qualifying stay to be only two days, and skilled nursing coverage is denied entirely.
When you do meet the three-day threshold, Part A covers up to 100 days per benefit period in a skilled nursing facility. The first 20 days are fully covered. Days 21 through 100 require a daily coinsurance payment that in 2024 runs over $200 per day. After 100 days, Medicare stops paying. This is skilled nursing care, meaning you need to require things like physical therapy, wound care, or intravenous medications. If you only need help with daily activities like bathing and dressing, Medicare will not cover the stay regardless of how long you were in the hospital.
A study examining what happens when the three-day rule is enforced found that reinstatement of the requirement led to longer hospital stays of about five and a half additional percentage points’ worth of patients staying three or more days, without reducing skilled nursing facility use, lowering Medicare spending, or improving patient outcomes like rehospitalization or mortality.2PubMed Central. Changes in Inpatient and Skilled Nursing Facility Care After the Medicare 3-Day Rule Reinstatement In other words, the rule adds cost without producing a clear benefit for patients or taxpayers.
What Medicare Explicitly Excludes
The gaps most people know about are dental care, routine eye exams, and hearing aids. Medicare was designed in 1965 and these services were excluded from the start, reflecting a now-outdated view that they were not truly “medical.” The consequences of those exclusions have been well documented. Medicare beneficiaries who lack dental coverage are roughly twice as likely to end up in an emergency department for nontraumatic dental problems compared with people who have commercial insurance.3JAMA. Consideration of Dental, Vision, and Hearing Services to Be Covered Under Medicare Emergency rooms can treat pain and infection, but they cannot perform the routine care that would have prevented the visit in the first place.
The exclusion of hearing aids is similarly consequential. Untreated hearing loss is linked to social isolation, cognitive decline, and falls. Original Medicare does not cover hearing exams for the purpose of fitting hearing aids, nor the devices themselves. Some Medicare Advantage plans include limited hearing benefits, but the coverage varies wildly by plan and region.
Beyond the “big three,” Medicare also does not cover:
- Long-term custodial care: If you need ongoing help with daily activities like eating, bathing, or dressing, and do not require skilled medical care, Medicare will not pay for it whether that care is provided at home, in an assisted living facility, or in a nursing home. This is the gap that financially devastates many older adults and their families. Medicaid, not Medicare, is the primary public payer for long-term custodial care, and qualifying for Medicaid generally requires having very limited income and assets.
- Cosmetic surgery: Procedures performed purely for appearance rather than to correct a functional problem or treat an injury are excluded.
- Care outside the United States: With very narrow exceptions involving emergencies near the Canadian or Mexican border, Medicare does not cover medical care received abroad.
- Most chiropractic services: Medicare covers manual manipulation of the spine to correct a subluxation but does not cover other chiropractic services, tests, or X-rays ordered by a chiropractor.
Preventive Services That Are Covered
One area where Medicare coverage has expanded significantly is preventive care. Since 2011, Medicare has fully covered annual preventive care visits with no cost-sharing for the beneficiary, a change that came with the Affordable Care Act.4PubMed. Medicare annual preventive care visits: use increased among fee-for-service patients, but many do not participate These visits, sometimes called “wellness visits,” are designed for health risk assessments, screening schedules, and advance care planning. They are not the same as a sick visit or a full physical exam, which is a distinction that sometimes leads to unexpected bills when a visit shifts from preventive to diagnostic.
Part B also covers a range of specific screenings at no cost to you, including mammograms, colonoscopies, prostate cancer screenings, cardiovascular screenings, diabetes screenings, and certain vaccinations. Flu shots, hepatitis B shots, and pneumococcal vaccines are covered under Part B with no copay. Other vaccines, including the shingles vaccine, are covered under Part D, which means you may have a copay depending on your drug plan.
The catch with preventive coverage is that the moment a screening finds something and your doctor acts on it during the same visit, the visit can be reclassified as diagnostic. If a polyp is found and removed during a screening colonoscopy, you may be billed coinsurance for the procedure even though the colonoscopy itself would have been free had nothing been found. This reclassification has been a source of confusion and frustration for beneficiaries, and legislative efforts have tried to address it, though the rules remain complicated.
Prescription Drug Coverage Under Part D
Medicare did not cover outpatient prescription drugs at all until Part D was added in 2006. Today, Part D is delivered through private insurance plans, each with its own formulary, which is the list of drugs the plan covers, and its own tier structure, which determines how much you pay for each drug.
The standard Part D benefit design illustrates how cost-sharing works. After meeting an annual deductible, beneficiaries typically pay about 25% of brand-name drug costs during both the initial coverage phase and the coverage gap (once called the “donut hole”). Once your total out-of-pocket spending crosses a catastrophic threshold, your share drops to 5% of brand-name costs or a small fixed copay, whichever is greater.5JAMA Network Open. Coverage, Formulary Restrictions, and Out-of-Pocket Costs for Sodium-Glucose Cotransporter 2 Inhibitors and Glucagon-Like Peptide 1 Receptor Agonists in the Medicare Part D Program Recent legislation has capped total annual out-of-pocket drug spending, which provides meaningful relief for people taking expensive medications.
Not every drug is on every plan’s formulary. Plans frequently use tools like prior authorization, quantity limits, and step therapy (requiring you to try a cheaper drug first) to manage costs. If a drug you need is not on your plan’s formulary, you can request an exception, but the process is not simple and is not guaranteed to succeed. This is one reason choosing the right Part D plan matters more than most people realize. A plan that is cheap in premiums but excludes your medications can end up costing far more than a plan with a higher premium and better formulary coverage.
Mental Health Services
Medicare does cover mental health care, including inpatient psychiatric hospital stays under Part A and outpatient therapy, psychiatrist visits, and certain psychological testing under Part B. However, spending on mental health within Medicare has historically been a small fraction of overall program expenditures. Data from the late 1980s showed that less than 3% of Medicare’s budget went to mental health services, compared with 20% to 30% of spending by private insurers at the time.6PubMed Central. Medicare’s mental health benefits: coverage, use, and expenditures
Coverage has expanded since then. The Mental Health Parity and Addiction Equity Act has pushed Medicare Advantage plans toward more equitable mental health coverage, and coinsurance for outpatient mental health was reduced from 50% to the standard 20% in 2014. Still, practical barriers persist. Many psychiatrists do not accept Medicare because reimbursement rates are lower than private insurance, which means finding a provider who takes your coverage can be a challenge, especially in rural areas. Inpatient psychiatric hospital care under Part A is limited to 190 lifetime days in a freestanding psychiatric hospital, a restriction that does not apply to psychiatric units within general hospitals.
Home Health Care and Hospice
Medicare covers home health services under specific conditions. To qualify, you must be homebound, meaning your condition makes it difficult to leave home without assistance or special transportation. You must need skilled nursing care on an intermittent basis, or physical therapy, or speech therapy. A physician must establish and periodically review your plan of care, and the services must be provided by a Medicare-certified home health agency.7PubMed Central. Eligibility for home care certification: what clinicians should know If you meet all those requirements, the benefit covers part-time nursing, therapy, medical social services, and some home health aide services at no cost to you. It does not cover 24-hour home care, meal delivery, or homemaker services like cleaning and laundry.
Hospice care under Part A covers a broader set of services for people who are terminally ill. To be eligible, you must be entitled to Part A and certified by a physician to have a life expectancy of six months or less if the illness follows its expected course. Once enrolled, Medicare covers medications related to the terminal diagnosis, nursing care, physician services, physical therapy, social work, and counseling.8Hospice and Palliative Medicine and Supportive Care Flashcards. Hospice Approach to Palliative Care It also covers short-term inpatient respite care to give family caregivers a break. What hospice coverage does not include is treatment aimed at curing the terminal illness. You can still receive Medicare-covered treatment for conditions unrelated to the terminal diagnosis.
An important practical note: electing hospice does not mean you have given up all medical care. If you develop pneumonia or break a bone and those conditions are unrelated to your terminal illness, Medicare still covers treatment for those problems through the standard benefit. The hospice election only shifts how your terminal condition is managed.
Medicare Advantage and Prior Authorization
More than half of all Medicare beneficiaries are now enrolled in Medicare Advantage plans. These plans must cover everything that Original Medicare covers, but they can add extra benefits and impose additional rules. The most consequential rule is prior authorization, which requires you or your doctor to get approval from the plan before receiving certain services.
Prior authorization has become a major source of friction. In 2021 alone, more than 35 million prior authorization requests were submitted to Medicare Advantage plans. Denial rates vary substantially across plans, and while only a small percentage of denials get appealed, more than 80% of those appealed denials are overturned.9PubMed Central. Improving Prior Authorization in Medicare Advantage That overturn rate strongly suggests that many initial denials block care that should have been approved in the first place. If you are in a Medicare Advantage plan and a service is denied, appealing is often worth the effort, though the process takes time and energy that sick patients may not have.
The tradeoff with Medicare Advantage is real. You may get dental, vision, or hearing benefits that Original Medicare does not offer, and your out-of-pocket maximum provides a financial ceiling that Original Medicare lacks. But you may also face narrower provider networks, referral requirements, and prior authorization delays that do not exist in Original Medicare. Whether Medicare Advantage or Original Medicare with a Medigap supplement works better depends heavily on your health, your doctors, and where you live.
Telehealth Coverage
Before the COVID-19 pandemic, Medicare’s telehealth rules were highly restrictive. Coverage was largely limited to beneficiaries in rural health professional shortage areas, and the visit had to take place at a designated clinical site, not the patient’s home.10PubMed Central. Medicare Payment Rules and Telemedicine The pandemic triggered emergency waivers that dramatically expanded telehealth access, allowing beneficiaries to receive covered telehealth visits from home regardless of where they lived.
Many of those expanded telehealth flexibilities have been extended through legislation, but their long-term status remains subject to congressional action. If you currently rely on telehealth visits for ongoing care, it is worth staying aware of whether current rules are permanent or operating under a temporary extension. Mental health services in particular have seen sustained telehealth use, and there has been strong political support for maintaining telehealth access for behavioral health, even if other telehealth expansions are scaled back.
How New Treatments Get Approved for Medicare Coverage
When a new medical device or therapy is approved by the FDA, that does not automatically mean Medicare will cover it. The Centers for Medicare and Medicaid Services (CMS) makes separate coverage decisions through a process called national coverage determinations (NCDs). CMS evaluates clinical evidence independently and sometimes reaches different conclusions than the FDA about whether a product’s benefits justify its costs for the Medicare population.
A study examining coverage decisions between 2005 and 2016 found that CMS evaluated 27 original clinical trials when making coverage decisions for 12 medical products, while the FDA reviewed 22 pivotal trials for those same products. Only about half of the trials CMS examined were the same ones the FDA had reviewed.11PubMed Central. Evidence supporting FDA approval and CMS national coverage determinations for novel medical products, 2005 through 2016 This divergence means that FDA approval is a necessary but not always sufficient step for Medicare coverage. Some treatments that are approved and on the market are not covered by Medicare, or are covered only under restrictive conditions like “coverage with evidence development,” where Medicare pays for the treatment only if the patient is enrolled in a qualifying clinical study.
This gap between FDA approval and Medicare coverage has been particularly visible with expensive new therapies, including certain cancer treatments and Alzheimer’s drugs. For beneficiaries, the practical implication is that hearing about a new treatment on the news does not mean Medicare will pay for it when you ask your doctor about it.
Help for Low-Income Beneficiaries
If your income and assets are limited, several programs can reduce or eliminate the cost-sharing that makes Medicare unaffordable for some people. Medicare Savings Programs help pay Part B premiums, deductibles, and coinsurance. The Part D Low-Income Subsidy, sometimes called “Extra Help,” reduces prescription drug costs for qualifying beneficiaries.12Innovation in Aging. Medicare Savings Programs, Part D Low-Income Subsidy, and Characteristics of Medicare Beneficiaries
These programs are underused. Many people who qualify do not apply, sometimes because they do not know the programs exist and sometimes because the application process involves paperwork through state Medicaid offices. If you are on Medicare and struggling with premiums, copays, or drug costs, checking your eligibility for these programs is one of the most impactful financial steps you can take. Your local State Health Insurance Assistance Program (SHIP) provides free counseling to help navigate the options. Eligibility thresholds vary by state and are updated annually, so even if you were previously told you did not qualify, your situation or the income limits may have changed.