Many people associate the month of October with changing leaves and pumpkin spice. But there's an important event that kicks off in October that seniors on Medicare should know about. It's open enrollment, and it runs from Oct. 15-Dec. 7 every year. Here are some aspects of open enrollment to keep in mind.

1. It's for existing enrollees only

Your initial Medicare enrollment window begins three months before the month of your 65th birthday and ends three months after that month. So all told, you get a seven-month time frame to enroll.

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But if you haven't yet signed up for Medicare, whether because you're not yet of age or you've been sticking with your group health plan at work to retain your HSA contribution privileges, then there's nothing for you to do during open enrollment. This period is for current Medicare enrollees to review their coverage and make changes. It's not for new enrollees to first sign up.

2. You can make changes to your Part D plan

Not so happy with your current Part D drug plan? Open enrollment is a great opportunity to dump your existing coverage and sign up for a new plan. And there are certain things you'll want to keep in mind when going this route.

First, review any upcoming changes to your existing plan, as outlined on the change notice you should receive from your current plan administrator (if you don't have that document in hand by mid-October, be sure to put in a call and follow up). It may actually be that your current plan is changing for the better, in which case you may want to keep it.

Next, compare your plan choices based on the medications you take. Medicare Part D plans group drugs into different tiers, and your out-of-pocket costs for those medications will hinge on how your prescriptions are ranked. It pays to compare numbers to see where you stand to save the most.

Finally, pay attention to plan ratings. Medicare uses a star rating system to rank Part D drug plans, with five stars being the best and one star being the worst. You shouldn't sign up for a new plan based on its rating alone. But if you're torn between two Part D plans, it could pay to err on the side of the plan with the better rating.

3. It pays to start your research early

Although you get until early December to make changes to your Medicare coverage, you don't want to wait too long to begin doing your research. Not only can enrollees make changes to their Part D coverage during open enrollment, but it's possible to move over to Medicare Advantage, swap one Advantage plan for another, or dump Advantage entirely in favor of Medicare Parts A and B plus a Part D drug plan.

All of these decisions are important ones to make. And they're choices that have the potential to impact your finances and health in a very big way. So begin exploring your options once open enrollment kicks off in mid-October. That way, you'll have time to explore your choices without undue stress.

Open enrollment is an important period of time for Medicare enrollees. Do what you can to make the most of it, because the right choices during open enrollment could set you up to save money on healthcare in 2024.