The Medicare open enrollment period runs from October 15 through December 7 each year. During this period, people on Medicare have the opportunity to make a change in their coverage.

Medicare Part C plans, known as Medicare Advantage plans, are private health insurance plans, mainly HMOs and PPOs, for people enrolled in Medicare. If you enroll in a Medicare Advantage plan, you still have Medicare, but you get all of your Medicare-covered benefits through a private plan. Most Medicare Advantage plans also cover prescription drugs and may cover other services, like vision, dental, and hearing. If you have Part A and Part B and are covered under the traditional Medicare program, then you do not need to sign up for a Medicare Advantage plan during Open Enrollment unless you want to get your Medicare benefits through a private plan.

Medicare Advantage plans restrict the health care providers that enrollees see (provider networks) whereas beneficiaries in traditional Medicare may see any doctor that accepts Medicare, without needing prior authorization or a referral from their primary care doctor.

11.9 million American seniors opt in to purchase a Medicare Supplement (Medigap) insurance plan. But choosing a plan is confusing. I read a study that said some of us overpay by thousands of dollars and the data shows that over 3,500 insurance companies overcharge. To give you just a few examples cited by the study:

—A 65-year-old woman in Idaho shopping for a Plan F or H could pay $2,004.08 per year from one provider, or $244.00 per year from another. A difference of $1,760.08.

—A 75-year-old male living in New Hampshire, purchasing a Plan F could pay $8,121.96 per year for that coverage. Or, if he had all the information, he could pay $1,820.28 per year for the exact same coverage and save $6,301.68.

—A 75-year-old male living in Pennsylvania, looking for a basic Plan A, might pay $11,801.64 per year if his insurance agent recommends one particular provider, or he could go with the least expensive provider and only pay $958.00 per year. Saving $10,843.64.

Know that all Medicare Supplement insurance plans are standardized by the government and all companies provide the exact coverage. Why would you want to pay more than you need for the exact same coverage? So, shop around.

You can learn about coverage options (without a computer) by calling 1-800-MEDICARE (1-800-633-4227), or by speaking with someone at your local State Health Insurance Assistance Program (SHIP).

SHIPs offer local, personalized counseling and assistance to people with Medicare and their families. You can call 877-839-2675 to get the phone number for the SHIP in your state.

You can also use the Medicare Plan Finder, a searchable tool on the Medicare.gov website. You can compare Medicare Advantage plans, Medicare Part D plans, and Medigap supplemental policies. Or call 1-800-MEDICARE (1-800-633-4227).