Medicare is a big deal. Offering health insurance for those 65 and older, as well as younger folks with certain disabilities or End-Stage Renal Disease, it serves more than 65 million people. It's valued highly by enrollees and is eyed greedily by scam artists as well.

Here are five Medicare scams to be aware of and to avoid.

An older person sitting at home is leaning on a cane and looking very serious.

Image source: Getty Images.

1. May I help you?

Many seniors have gotten scammed by responding to people who knock on their door saying they're from Medicare and can help, perhaps offering tempting "free" services or just asking to verify information. Others are approached similarly but via email, phone, or even texts. Medicare does not cold-call people in person or otherwise. If they're truly calling you, it's because you called them first, perhaps with a question.

Note, too, that scammers these days have gotten very good at being convincing. They may have some of your information, such as your address or your Social Security number due to a data breach somewhere, and they can get you to trust them by sharing that. Stay skeptical! Even if the email or ID card looks legit, doubt it -- and verify, or better yet, just say no.

2. Your Medicare plan has been canceled!

Another scam is contacting a senior and frightening them by announcing that their Medicare plan has been canceled -- or may be canceled soon -- and they'll be in deep trouble if they don't go along with whatever the scammer is asking of them.

Know that Medicare plans generally don't just get canceled, leaving enrollees in the lurch. They may get canceled if you fail to pay your premiums, though. One way to avoid that occurrence is to have your premiums taken out of your Social Security benefits directly.

3. Want some free products or medical services?

Read up on your Medicare plan to see just what it offers you. For example, "original" Medicare covers things such as inpatient hospital care, annual wellness visits with your doctor, some in-home health services, some mental health treatments, preventive screenings, wheelchairs, oxygen equipment, and much more. It does not cover dental, hearing, or vision services -- though many Medicare Advantage plans do cover those -- along with everything covered by original Medicare.

If someone is approaching you offering additional services or products for free or at a big discount, don't believe them. You can always call Medicare, too, to see whether a certain product or service is covered by your plan.

4. You need a new Medicare card

A few years ago, Medicare enrollees did receive replacement Medicare cards featuring a randomized ID number instead of the Social Security numbers previously used. That event inspired some scammers to start targeting seniors, telling them they need a replacement card (perhaps one with a chip -- though Medicare cards do not use chips) or that they need to activate their current card by telling the scammer their new number. Don't fall for it if someone is asking you to reveal or confirm your Medicare number. Enrollees should have their new cards by now and shouldn't need to replace them again (unless they lose them).

5. Here's a better -- or cheaper -- plan for you!

One more scam is when someone is trying to get you to sign up for a special, better Medicare plan -- perhaps telling you you've been pre-approved for it. This scam is most prevalent in autumn during the annual Medicare open enrollment period when enrollees can switch between plans.

Resist this scam, too. It is good to comparison-shop and weigh your options each year during the enrollment period, but do your own homework on plans available to you. You can get a lot of research done right at Medicare.gov's website.

General tips for thwarting scammers

If you keep the following tips in mind, your chances of being scammed should shrink significantly:

  • Don't respond to unsolicited calls, emails, or texts. If you're interested in some Medicare information, find it on your own.
  • Don't give out your personal information, such as your Medicare number, Social Security number, address, or birthday to anyone unless you're sure you know who they are.
  • Don't sign up for or accept any gifts, services, or health plans you're offered out of the blue.
  • Don't let yourself get flustered, frightened, or pressured by an unsolicited contact.
  • When in doubt, just contact Medicare itself on your own, at 1-800-MEDICARE (1-800-633-4227) or at medicare.gov.
  • Report anyone pretending to be from Medicare, too, by contacting Medicare and also contacting the Federal Trade Commission (FTC) at ReportFraud.ftc.gov.

In general, the more you know about Medicare, the less likely it is that you'll end up scammed. It's worth keeping up with Medicare in the news, too, to see how it might be getting strengthened or weakened.