It's a big misconception that once you enroll in Medicare, you can expect your healthcare expenses to decline. For many people, the opposite happens.

That's not just because of the many expenses Medicare enrollees are subject to. It's also that health issues tend to arise with age. That combination could put a huge strain on your retirement savings.

For this reason, it's important to manage your Medicare benefits wisely. A big part of that means taking advantage of the program's annual open enrollment period.

Medicare's open enrollment period runs from Oct. 15 through Dec. 7 every year. Here are a few things all retirees need to know about it.

1. You can't sign up for Medicare for the first time during open enrollment

If you're retired and are old enough to sign up for Medicare, you may be planning to do so during fall open enrollment. But you should know that open enrollment is for existing Medicare participants only.

Your initial window to sign up for Medicare spans seven months, starting three months before the month of your 65th birthday and ending three months after that month. If you missed that initial window, and you don't qualify for a special enrollment period, then you may need to wait until Medicare's general enrollment period to sign up for coverage. That takes place Jan. 1 through March 31 each year.

2. You should review your plan choices, even if you're happy with your coverage

A lot of people get excited about Medicare Open Enrollment because they're frustrated with their Part D or Medicare Advantage plan and can't wait to switch. But even if you have no gripes about your current plan, it still pays to review your options this October.

It may be that you can afford your Part D plan premiums and copays just fine. But what if there's a cheaper option? Why wouldn't you want to save yourself a little money? Plus, if your healthcare needs have changed at all during the year, then it's especially wise to review your plan choices to see if there's a better match.

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3. You should consider switching Medicare Advantage plans if you're not using your supplemental benefits

A big reason a good number of seniors opt for Medicare Advantage over original Medicare is that these plans commonly offer supplement benefits on top of what original Medicare covers. Original Medicare won't pay for dental care, eye exams, or hearing aids, for example. But it's common for Medicare Advantage plans to pick up the tab for these services.

Some Medicare Advantage plans also go well beyond dental, vision, and hearing services, offering benefits that include fitness club memberships and meal delivery services. But if you're paying for a Medicare Advantage plan with lots of benefits, it's important to make sure you're getting your money's worth. If you're not using your plan's supplemental benefits, then it could pay to make a change.

You may find that another Medicare Advantage plan offers the more basic supplemental benefits you need at a lower cost. Or, if you need specialized benefits, it may be that your current plan doesn't offer them, but another plan does.

Some seniors opt not to participate in Medicare's open enrollment period because they find the process of reviewing plan choices overwhelming. If you feel the same, start early. Begin doing your research in mid-October so you have plenty of time to compare different options. Putting in that effort could lead to big savings on healthcare in 2025.

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