In a world filled with health care complaints, being pleased with your Medicare coverage puts you ahead of the game. But being satisfied doesn’t mean there aren’t areas for improvement, and what worked for you in 2017 may not be right for 2018.

Though it’s difficult to know what the future holds, if you foresee events such as a surgery or changes in your prescription drug regimen, planning in advance with the right Medicare policy could help you save substantially on your medical bills.

Medicare open enrollment, which will last until Dec. 7, is a chance for all beneficiaries — even those who are pleased with their plan — to explore their options.

During this period, you can drop your current Medicare Advantage plan in favor of another, revert to Original Medicare, leave Original Medicare and opt for Advantage, add or change Part D prescription drug coverage or purchase a Medigap or supplemental policy.

Changes made during the open enrollment period will take effect on Jan. 1.

[See: How to Pick a Health Insurance Plan.]

But, I’m Happy — Why Should I Change?

Reviewing your current coverage doesn’t necessarily mean you’ll make any changes, but rather that you’re open to the idea that something better might be available.

Regardless of what coverage you have, you can search all Medicare plans, including prescription drug benefits — known as Part D Medicare — with the Medicare Plan Finder tool, or call 800-MEDICARE with questions.

If You Have Original Medicare

This is coverage managed by the federal government and consists of Part A (hospital insurance) and Part B (medical insurance) coverage. Your policy is accepted anywhere that takes Medicare, and you don’t have to worry about seeing medical providers in a specific “network,” though you will be responsible for deductibles, coinsurance and a premium for Part B coverage.

Read through this year’s “Medicare & You” handbook on Medicare.gov to understand what’s covered under free preventive services (such as mammograms and flu shots) and how much you’ll pay out-of-pocket for certain treatments, exams and procedures.

Though most people don’t pay a premium on Part A coverage, Part B is another story. Costs are not changing in 2018, however, and most monthly Part B premiums will remain at $134.

Understand that Original Medicare doesn’t cover everything, and you may want to consider a supplemental policy for needs such as prescription drugs, eyeglasses, dental care (including dentures), hearing aids and exams, and long-term care. Another option is a Medigap policy, which can help with out-of-pocket expenses such as deductibles, copays and coinsurance. The time to sign up for a Medigap plan is within the first six months of becoming eligible for Medicare. After that, insurers can factor any health conditions you have when deciding whether to sell you a plan.

You may consider switching to Medicare Advantage (also known as Part C) if you want a single plan that includes services such as prescription drug benefits, dental or vision coverage.

If you’ve reviewed the information and want to stay with Original Medicare, no action is required on your part; your current coverage continues.

[See: Infographic: How to Read Your Hospital Bill.]

If You Have Medicare Advantage

Medicare Advantage includes both Part A and Part B coverage and is managed by private insurance companies rather than the government. These plans include PPOs and HMOs and resemble other private insurance plans sold to people of all ages. As with other types of health insurance, Medicare Advantage plans can vary dramatically in costs and coverage.

Under Medicare Advantage, you generally have to visit in-network medical providers or risk paying more out of pocket. You’ll may also pay a monthly premium and be subject to deductibles, copays and coinsurance. Nearly 30 percent of these 2018 Medicare Advantage plans will have a $0 premium, according to a HealthPocket market analysis.

Unlike Original Medicare, most Part C plans include prescription drug coverage. Some may also offer dental and vision benefits not available through Original Medicare. In addition, Medicare Advantage plans have annual caps on out-of-pocket expenses.

You should have already received a letter from your insurance company outlining any changes you can expect in 2018. If you haven’t received an Annual Notice of Change or Evidence of Coverage document from your insurer, call to request a copy. These notices will include any cost or coverage changes that you should be aware of, so read them and the “Medicare & You” handbook carefully.

The average monthly premium for a Medicare Advantage plan in 2018 will be $30, which is 6 percent less than this year. However, premiums and deductibles vary greatly by region and plan.

It’s also important to check your provider network and that the doctors you see still participate.

Analyzing your health care needs for next year and looking at a variety of plans during open enrollment will help ensure you have the best coverage for 2018. In addition to using the Medicare Plan Finder at Medicare.gov, you can browse Part C plans on the websites of private insurers.

[See: How to Help Aging Parents Manage Medications.]

If You Have Part D, Prescription Drug Coverage

While Medicare Advantage plans typically include their own prescription drug coverage, under Original Medicare, you must purchase a separate Medicare Part D plan. This insurance is sold by private insurance companies with costs and coverage varying from policy to policy.

If you already have Part D, review your current coverage and additional available plans even if you were pleased in 2017. According to a survey of 30,000 users, eHealthMedicare.com found that more than 90 percent of beneficiaries enrolled in some type of prescription drug coverage plan could be overpaying.

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Satisfied With Your Medicare? Why You Should Still Review Your Plan originally appeared on usnews.com

Update 11/06/17: This story was originally published on Nov. 4, 2014. It has been updated by Lisa Zamosky.