Although Part B covers most kinds of outpatient care, there are a few important exceptions. The first is routine physical exams (beyond the initial wellness exam), despite their preventive value. Similarly, Part B doesn't cover vaccinations or immunizations, except for pneumonia and flu shots.

Part B covers only care that is medically necessary, which Medicare interprets as excluding most chiropractic and other types of alternative care, such as acupuncture, acupressure, and homeopathy. It also excludes elective or cosmetic surgery or other treatments.

Nor is there any Part B coverage for routine eye or hearing exams, and none for hearing aids, eyeglasses, or contact lenses (except following cataract surgery). Treatment for diseases of the eye or ear, however, can be covered if provided by a medical doctor. Dental work is not covered.

Finally, Part B doesn't cover any drugs, prescription or otherwise, that participants take at home. Instead, prescription medication can be partially covered by a Medicare Part D insurance policy.