Medicare's open enrollment period is now open us. From now through early December, seniors on Medicare have an opportunity to make changes to their coverage. And that extends to Medicare Part D, which covers prescription drugs.

In 2022, the average monthly premium for Part D coverage will be $33 per month, up from $31.47 in 2021 (higher earners could pay a lot more, though). But that doesn't mean all Part D plans are created equal. And it also doesn't mean you should keep your current Part D plan, even if it seems cost-effective and you're relatively happy with it. Here are a few signs that a change to your Part D coverage may be in order.

Bottle of pills spilled over

Image source: Getty Images.

1. Your medications have been bumped into a more expensive tier

All Medicare Part D plans have formularies that group different drugs into different categories, or tiers. The higher the tier, the higher the copay at hand.

It could be the case that the medications you take fell into one tier for the current year but are being pushed into a higher tier for 2022. And if that's the case, you may want to find a plan where you won't pay as much for your medications.

2. You're on new medications

It could that your current Part D drug plan's formularies aren't changing, or that they're not changing in a way that impacts you. But what if your needs have changed? If you're no longer taking certain medications, it could mean that you're able to sign up for a less expensive Part D plan.

3. You're struggling to find in-network pharmacies

Seniors who take medication on a long-term basis commonly access their prescriptions through mail order services, which can not only be more cost-effective, but also, save them some trips to the pharmacy. But your medication needs may not always be predictable. You could get sick or end up needing a specific medication on a short-term basis. And that means you also need decent access to nearby pharmacies.

But pharmacy accessibility can vary by Part D plan. That's because these plans require you to use an in-network pharmacy or otherwise face exorbitant costs for going out of network. And so if your existing Part D plan doesn't have enough convenient pharmacies, that alone could be a good reason to switch.

Set yourself up for 2022

Being on the wrong Part D plan could make your prescription coverage more expensive. And whether you're on a fixed income that's mostly Social Security or have a decent nest egg at your disposal, that just doesn't make a lot of sense.

It pays to explore your options for switching your Part D coverage during open enrollment. There's a plan finder tool on Medicare.gov that will allow you to search for Part D plans based on your geographic location and see how they're rated. Take some time to review your options and crunch the numbers. Doing so could end up saving you a world of money, and stress, in the coming year.