If you don't sign up for Medicare when you're first eligible, you may have to pay a penalty if you decide to enroll later.  You can sign up for Medicare during your Initial Enrollment Period, the Annual Enrollment Period (October 15-December 7) or during a Special Enrollment Period if you meet certain conditions. Additionally, you may have a gap in coverage if you don't have other insurance. 

You can sign up for Medicare during your Initial Enrollment Period, which begins three months before the month you turn 65, includes the month you turn 65, and ends three months after the month you turn 65. You can also sign up during the Annual Enrollment Period (October 15-December 7) or during a Special Enrollment Period if you meet certain conditions.

To sign up for Medicare, you can:

• Visit the Social Security Administration's website to apply online
• Call the Social Security Administration at 1-800-772-1213
• Visit a local Social Security office in person

When you sign up, you'll need to provide information such as your birth date, Social Security number, and address. You'll also need to choose whether to enroll in Original Medicare (Part A and Part B) or a Medicare Advantage plan (Part C).

It's important to note that if you're already receiving Social Security benefits, you'll automatically be enrolled in Medicare Part A and Part B at age 65. However, you will still need to sign up for a Medicare Prescription Drug Plan (Part D) if you want coverage for prescription drugs.

The cost of Medicare varies depending on the type of coverage you have. Original Medicare Part A typically doesn't have a monthly premium for most people, but Part B does. Medicare Supplements, Medicare Advantage plans (Part C) and Medicare Prescription Drug plans (Part D) typically have a monthly premium in addition to deductibles and copayments.

Here are some of the costs associated with Original Medicare (Part A and Part B):

• Part A: Most people don't pay a monthly premium for Part A (hospital insurance) because they or a spouse have paid Medicare taxes while working. However, if you don't qualify for premium-free Part A, you may have to pay.

• Part B: The standard monthly premium for Part B (medical insurance) can vary. You may pay more or less depending on your income.

• Deductibles: Original Medicare has different deductibles for Part A and Part B that can change annually. 

• Copays: After you meet the deductibles of Original Medicare, you a be responsible for copays and coinsurance. A Medicare Supplement plan can cover these copays and coinsurance.

Medicare Supplement plans, also known as Medigap plans, are private insurance plans that help cover some of the out-of-pocket costs not covered by Original Medicare (Part A and Part B). These plans are standardized by the federal government, meaning that each plan must offer the same basic benefits, regardless of which insurance company is offering the plan.

Medicare Advantage plans (Part C) are offered by private insurance companies and must cover at least the same benefits as Original Medicare. The costs of these plans vary depending on the specific plan and the location, generally these plans have a monthly premium and may have an annual out of pocket maximum.

Medicare Prescription Drug plans (Part D) are also offered by private insurance companies and the costs vary depending on the specific plan, the location and the drugs you need. The cost of these plans usually includes a monthly premium, a yearly deductible, and copays or coinsurance for each prescription.

It's important to note that costs can change each year, so it's a good idea to review your coverage and costs each year during the Annual Enrollment Period (October 15-December 7)