6. Although the good news is the cost-of-living adjustment is 2.8%, the highest in six years, inflation is higher, too. Miller noted that Part B premiums will go up anywhere from $1.50 to $135.50 per month.

Medicare plan considerations

Here are 6 takeaways on what people need to think about with their Medicare plans, from a conversation between Morningstar's Christine Benz, director of personal finance, and Mark Miller, a Morningstar contributor who specializes in retirement issues:

1. There’s another choice aside from the traditional Medicare plan: Medicare Advantage.

Whereas the traditional Medicare is a “fee-for-service” plan, Medicare Advantage is an all-in-one plan that may also include vision and dental insurance.

It’s more like an HMO or PPO plan with in-network services.

“Medicare Advantage works really well for younger, healthier seniors,” Miller said.

2. Retirees should review their Medicare Part D plans yearly, Miller stated, as “plans can change from year to year. The premiums can change, the out of pockets can change, what’s covered can change. The provider networks can change.” He added that by reviewing options yearly, money can be saved.

3. The best time to purchase Medigap insurance — a supplemental plan that captures out-of-pocket expenses — is when retirees first enroll “because it is an open enrollment period at that time and the insurers cannot do so-called medical underwriting, meaning charge you more because of the health condition or even turn you away for coverage,” Miller said.

4. Retirees have until the end of March 2019 to change their Medicare Advantage plan if they don’t like it, or even move back into the traditional Medicare plan.

5. Premiums for part D plans are going up on average 2% in 2019. However, that’s an average: Some could go up as much as 10%. Retirees can check their options at Medicare.gov.

6. Although the good news is the cost-of-living adjustment is 2.8%, the highest in six years, inflation is higher, too. Miller noted that Part B premiums will go up anywhere from $1.50 to $135.50 per month.