October may be the season of leaves changing colors, Halloween, and all things pumpkin spice, but for seniors, it's a very important time of year. That's because October is when Medicare's open enrollment period begins, and if you're on Medicare, it's your big chance to make changes to your health coverage for the following year. And that's an opportunity you don't want to blow. As such, it's important that you steer clear of the following mistakes.

1. Not reviewing your Part D plan choices

If you've been signed up for the same Part D drug plan for years, you may be inclined to stick with it. But not reviewing your plan options could cost you. Even if your out-of-pocket expenses haven't risen under your plan, there may be a different plan out there for you that's more cost-effective, so it's worth putting in the time to explore the choices that are available for 2021. Furthermore, it's especially important that you review different Part D plans if your medication needs have changed, because there may be a less expensive plan that wasn't right for you in the past, but is appropriate now.

Diamond shaped sign reading open enrollment ahead on road with bright colored leaves

Image source: Getty Images.

2. Not reading your plan's notice of change

If you're enrolled in a Part D drug plan, your plan is required to send you an annual notice of change by late September. That notice should outline the various changes that will go into effect for the following year. It's imperative that you read through that document carefully to see if you'll be impacted.

It's common practice for drug plan formularies to change from one year to the year. These formularies group prescription medications into different tiers, and the higher the tier, the more money you'll pay. If a medication you take is suddenly pushed into a higher tier, that's something you'll want to know about. The same applies if your plan decides to drop coverage for the medication you're on.

3. Not getting a separate Part D plan from your spouse

Enrolling in the same Part D plan as your spouse might seem like a smart idea. That way, you're both subject to the same copays and rules. But if you and your spouse take different medications, then it could pay to see if it makes sense to sign up for different plans this fall. You may find that by splitting your coverage, you wind up spending a lot less in total.

Open enrollment, which begins on October 15 and lasts through December 7, offers a prime opportunity to set yourself up for a less expensive 2021, at least from a healthcare perspective. During this time, you can switch Part D plans, move to a new Medicare Advantage plan, swap Medicare Advantage for original Medicare, or move to Medicare Advantage from original Medicare. Spending too much on your Medicare coverage could take a toll on your retirement savings and put you in a position where you're struggling financially for no good reason, so make sure not to fall victim to the above mistakes this fall.