It is important for you to understand what standard Medicare covers and doesn't cover, so you avoid costly surprises later on. While traditional Medicare covers a good portion of your doctor and hospital bills, you'll still need other insurance, unless you end up qualifying for Medicaid. Medicaid is a federal medical insurance program for people with very low incomes and virtually no assets, which you could end up on if you don't have the proper insurance in the first place. Here's what Medicare doesn't cover:

• Most prescription drugs.

Medicare offers a prescription drug benefit. Premiums and deductibles vary by plan, and co-payment amounts depend on the amount of your drug costs. Individuals with low income and limited assets will get help paying the premiums and deductible.

• Routine physicals or routine dental work, dentures, glasses, routine eye exams or routine foot care, immunizations, and most other services which it considers preventive care.

Medicare covers some preventive services such as a one-time wellness physical exam upon enrolling in Medicare Part B, mammography, pap smears, diabetes screening test and outpatient self-management, prostate and colorectal cancer screening, bone density measurements, cardiovascular screening blood tests, and vaccines. Some Medicare HMOs and some of the plan options under Medicare Advantage may include additional services such as prescriptions, dental care, and eye care.

• Private duty nurses or homemaker services.
• The first three pints of blood.
• Cosmetic surgery
• Treatment that it doesn't consider medically necessary. Medicare can deny what it considers to be an unreasonable length of stay in a hospital. (It will pay only for those days it deems medically necessary.)
• It only pays charges that it considers are reasonable and customary. So you may have a bill from your doctor that exceeds Medicare's limit. Medicare will pay 80% of what it considers to be the normal charge for the service; you're required to pay the additional 20% plus the excess over the reasonable and customary charge (unless the doctor or supplier agrees to accept Medicare's approved amount as the total charge for services rendered).
• Skilled nursing care is limited and it does not cover custodial care. It won't pay long-term nursing home care costs or costs you incur by having an aide assist you with day-to-day basic living activities (dressing, eating, bathing or communicating). Neither Medicare nor Medigap insurance will pay for most nursing home care. See the section on Long-Term Care Insurance.
• Medical treatment outside the United States (except in limited cases).
• Experimental drugs or procedures.