Healthcare tends to be a significant expense for retirees. And for some seniors, the cost of medication can be exceptionally burdensome.

That's why it's so important to choose the right Medicare Part D plan. If you're enrolled in a Medicare Advantage plan, that plan should cover your prescription needs. But if you're enrolled in original Medicare (Parts A and B), you'll need separate drug coverage under Part D.

Meanwhile, Medicare's annual fall open enrollment period just kicked off on Oct. 15, and it will run all the way through Dec. 7. During this time, existing enrollees have the opportunity to make changes to their coverage. And you may want to make a change to your Part D plan if these circumstances apply to you.

A person pouring pills into their hand.

Image source: Getty Images.

1. Your plan has changed

At this point, you should've received a notice from your Part D plan administrator informing you of changes to your plan that are set to take place in 2023. If your plan is changing for the better, then great -- stick with it. But if it's changing for the worse, that's a sign that you may want to switch plans.

How might your plan change for the worse? Part D plans have formularies that group prescriptions into different tiers. If the medications you take are bumped into a higher tier for 2023, that could leave you on the hook for more expensive copays. And if your income is limited -- say, you mostly live on Social Security -- that could prove problematic. As such, a change might be in order.

2. Your needs have changed

Maybe your Part D plan is staying the same for 2023. But if your needs are changing, that alone should prompt you to look at other plans. It could be that you're going off one medication and starting another, or are going from a name-brand drug to a generic. You'll want to compare your costs under different Part D plans to see what makes the most financial sense.

3. There are savings to be reaped

Maybe your Part D plan isn't changing in 2023, and maybe your prescription regimen is staying exactly the same. That doesn't mean a new plan won't benefit you. It may simply be the case that there's a less expensive Part D out there than the one you're currently on, so it pays to do some digging.

The good news is that Medicare has a plan finder tool on its site that you can use for both Part D and Advantage plans. Better yet, listed plans have ratings attached to them so you can see how happy their enrollees tend to be.

Set yourself up with the right coverage for 2023

Healthcare may be one of your largest retirement expenses, so it's important to do what you can to whittle it down. By exploring your Part D plan options during open enrollment, you might manage to lower your costs, all the while gaining access to a more convenient network of pharmacies that makes it easier to get your hands on the prescriptions you need.