For many people, autumn is the season for enrollment in a medical insurance plan. Everyone, whether you’re 25 or 85, whether you’re covered through an employer plan, a state insurance exchange, private insurance or Medicare, should review their current coverage and compare it with the available options.

Insurance companies rewrite some parts of their plans every year; they change premium amounts, the drugs they subsidize, the amount of the deductible … health-care coverage is a moving target, and absent certain major life events, you usually have one shot at renewing or revising your coverage each year.

The moving part we want to illuminate here is the drug coverage offered by Medicare, the federal government insurance for people 65 and older, the disabled and people with certain disorders. These patients tend to use a disproportionate amount of drugs, so Medicare Part D, which covers medicine, is a particularly important financial component of overall coverage.

The list of drugs that are covered or subsidized by insurers is called the formulary, and if you regularly take a certain med, or an usually expensive drug, you want to ensure it’s in your plan’s formulary, and you want to know how much of the cost is subsidized. Formularies change, so don’t assume because your med was covered last year it will be next year. Or if it is, that you’ll receive the same subsidy.

Click here to learn more about Medicare Part D, how it works with other insurance and how to choose a plan. Read Patrick’s newsletter, “How to Make the Most of Turning 65” to learn more about Medicare generally.