What Medicare Part B generally covers
Part B generally helps cover medically necessary doctor services, outpatient care, preventive services, ambulance services, durable medical equipment, lab tests, imaging, and many services used to diagnose or treat medical conditions. It is the part most people use when they go to a doctor or receive care outside an inpatient hospital setting.
Why Part B timing matters
Part B usually has a monthly premium. In 2026, the standard Part B premium is $202.90 per month and the annual deductible is $283. Some people enroll as soon as they are eligible. Others delay Part B because they have active employer group coverage. The problem is that not all coverage lets you delay safely. Retiree coverage, COBRA, marketplace coverage, and small-employer coverage can create different issues.
How Part B cost sharing works
After the Part B deductible is met, Original Medicare generally pays 80% of the Medicare-approved amount for many covered Part B services, and you are responsible for the remaining 20% unless another coverage arrangement helps with that cost. That 20% exposure is one reason people compare Medicare Supplement and Medicare Advantage options.
Part B and late enrollment penalties
If you miss your proper Part B enrollment window and do not have qualifying coverage, you may face a late enrollment penalty and a coverage gap. That is why people turning 65, retiring, or leaving employer coverage should review timing before making assumptions. The penalty can last as long as you have Part B, so timing should not be guessed.
How Part B affects other Medicare choices
Part B is usually required before you can enroll in many Medicare coverage options, including Medicare Advantage and Medicare Supplement plans. It is also part of the baseline comparison when deciding whether Original Medicare with add-ons or Medicare Advantage is the better fit.
What to compare once Part B is active
Once Part B is in place, the next questions are practical: which doctors you want, what prescriptions you take, whether you travel, how much monthly premium you are comfortable with, and how you want to handle out-of-pocket risk.