Medicare is a critical healthcare program that millions of older Americans rely on. Every year, millions of people become eligible for Medicare for the first time, and you want to make sure that you know everything you need in order to take full advantage of the program.

Below, we'll share four things you ought to know about Medicare. They'll help you get started with the program and make the best decisions for your own personal situation.

Paper marked Medicare Enrollment Form, with a pen on top.

Image source: Getty Images.

1. Automatic enrollment vs. having to sign up for Medicare

In general, the Centers for Medicare and Medicaid Services try to make joining Medicare as easy as the agency can. If you're already getting Social Security benefits, then Medicare will coordinate with the Social Security Administration to sign you up for Medicare benefits automatically when you reach age 65. If you're eligible for automatic enrollment, you'll get signed up for hospital coverage under Medicare Part A as well as medical coverage under Part B. Some people don't want both of those coverage options, and if you're one of them, you'll need to take steps to avoid being signed up for parts of Medicare you don't want. Note that if you want prescription drug coverage under Medicare Part D, you'll need to sign up for a plan provider separately.

If you don't qualify for automatic enrollment, then you have several options to sign up for Medicare. You can visit a Social Security office in your area to sign up for Medicare, or you can call the SSA directly. Operators are available toll-free at 1-800-772-1213 on weekdays from 7 a.m. and 7 p.m., and those needing TTY services can call at 1-800-325-0778. The SSA also has an online app through which you can either sign up for Medicare only or apply for Social Security and Medicare in one fell swoop.

2. When you can sign up for Medicare

Most people become eligible for Medicare at 65, but you get to file for your coverage in advance of actually getting it. Medicare has an initial enrollment period that starts three months before you turn 65 and then extends beyond your 65th birthday for three more months. If you enroll before you turn 65, then you'll ensure that your coverage will start right on time without any delays. If you wait, then it could take up to three months for your Medicare to kick in.

However, just because you can sign up for Medicare doesn't mean it's always a good idea. If you still have private coverage through either your own employer or a spouse's employer, then you might be able to put off signing up for Medicare for as long as you still have that outside coverage. Then, when you or your spouse stop working and lose private health insurance, you can then qualify for a special enrollment period to sign up for Medicare without penalty. However, it's worth asking your employer to see what specific requirements apply in your particular situation.

3. Traditional Medicare vs. Medicare Advantage

Instead of the Medicare Part A and B coverage options listed above, you also have the right to sign up for an alternative known as Medicare Advantage. Sometimes referred to as Medicare Part C, Medicare Advantage is offered through private insurance companies whose coverage complies with the requirements that the Medicare program imposes. In general, you'll get hospital and medical coverage similar to original Medicare, but you'll also often get added features such as integrated prescription drug coverage and features like out-of-pocket maximums.

There are pros and cons to both Medicare Advantage and traditional Medicare, so it's worth a look at both programs to see which will work better for you. In some cases, though, Medicare Advantage is the simplest way to get all the coverage you want in a single package.

4. Get a free checkup on Medicare

The first thing you'll want to do once you get your Medicare coverage is to take advantage of your initial preventive visit. Medicare made that initial visit part of the program in order to get new participants off to a good start, ensuring that they get the healthcare they need and are aware of any potential problems.

The preventive visit is available during the first 12 months you're part of Medicare. It's intended to establish a baseline level for your health and give you an opportunity to get answers to health-related questions, so be sure to use it wisely.

Welcome to Medicare!

If you're eligible for Medicare in 2019, then congratulations! With all the resources available to give you more details about Medicare, you'll want to learn everything you can in order to make the most of your Medicare coverage both this year and in the future.