Medicare’s annual open enrollment period ended last month, but certain beneficiaries who regret their selection can get a do-over from now through mid-February. The Medicare Advantage disenrollment period runs from Jan. 1 through Feb. 14. During this time, beneficiaries in private Medicare Advantage plans can switch to Original Medicare and, if desired, select a Part D drug plan. This is the only move permitted: Those in Original Medicare can’t switch to Medicare Advantage and those already in Medicare Advantage can’t switch to a different Medicare Advantage plan. Unless those beneficiaries qualify for a special enrollment period, they will have to wait until the fall to make any changes to their coverage that will be effective at the start of 2018. The winter disenrollment period for Medicare Advantage may be easy to miss. It’s not accompanied by the same advertising blitz that characterizes the annual fall open enrollment, when the airwaves fill with commercials for Medicare Advantage and Part D drug plans. “It’s much less heralded,” says Joe DeLuca, director of sales at eHealthMedicare.com, a broker that helps consumers select private Medicare plans. But for those unhappy with their Medicare Advantage coverage, it’s an important chance to leave your plan, regardless of whether you enrolled years ago or during the recent open enrollment. (For tips on navigating Medicare in general, check out Money’s comprehensive guide.) Beneficiaries aren’t limited in the number of times they can take advantage of the Medicare Advantage disenrollment period during their lifetimes. Medicare Advantage, otherwise known as Part C, is coverage managed by private health plans that contract with Medicare. Nearly one-third of Medicare beneficiaries have chosen Medicare Advantage over Original Medicare, which consists of Part A hospital coverage and Part B doctor coverage managed by the government. These beneficiaries pay monthly Medicare Advantage premiums in addition to their Part B premium, although some Medicare Advantage plans charge nothing for premiums. (Most Medicare beneficiaries don’t pay any Part A premium.) There are a number of reasons why you might decide to scrap your Medicare Advantage plan. For starters, you might be unhappy with the plan’s network of doctors and hospitals. About two-thirds of these plans are HMOs, many of which limit coverage to a specific network of doctors and hospitals in a particular locale. What’s more, you may have to get a referral to see a specialist. While plans must pay for emergency care out of network, they generally won’t cover routine care elsewhere. A recent study shows that the hospital you go to can make a big difference in the quality of your care. Patients in poor-performing hospitals are three times more likely to die and 13 times more likely to experience complications than those in high-performing hospitals, according to a recent study by the Boston Consulting Group and other researchers published in the journal PLOSONE. The authors ranked the hospitals themselves and compared outcomes between the top 10% and the bottom 10%. While you may not have control of the hospital you’re taken to in an emergency, you do have a say over where you go for elective procedures, and you want to be sure you like your options. In addition, a Medicare Advantage plan might not be the best for your particular health needs. For example, Dr. Katy Votava, president and founder of Goodcare.com, says her clients on oxygen tend to get the most comprehensive coverage on Original Medicare paired with a Plan F Medigap supplement. Her firm helps people understand and select Medicare benefits. Most Medicare Advantage plans include drug coverage. If you’re switching to Original Medicare, you’ll likely want to select a Part D drug plan to replace the drug coverage you’re losing. Drug benefits under Medicare Advantage are structured similarly to Part D drug coverage, Votava says, so you’ll want to make sure you study the plan’s formulary, as the list of covered drugs is known. Don’t delay enrolling in a Part D plan: You may owe a late enrollment penalty if you go without drug coverage for any continuous period of 63 days or more. If you’re switching into Original Medicare, you may also want to buy a Medigap supplement plan. These plans cover out-of-pocket costs that Original Medicare does not. For example, some of the more comprehensive Medigap plans will cover both the Part A and Part B deductibles. In most states, Medigap supplement plans are medically underwritten. That means if you enroll in one outside your initial enrollment period when you first join Medicare, an insurer could deny you coverage or charge you more based on your particular pre-existing conditions. (New York is one of a handful of states that operate differently. Check your State Health Insurance Assistance Program to learn more about coverage in your state.) For this reason, don’t drop your Medicare Advantage coverage before enrolling in a Medigap plan. It might take you a couple of tries before you find a plan that will accept you, Votava says. Once accepted, you might still find that the coverage you want is outside of your budget. If you don’t like your options, you can always stick with Medicare Advantage. But if you’ve already dropped your Medicare Advantage, you’re out of luck—you can’t reenroll in your plan right after dropping it, Votava says.