Is a Common Medicare Mistake Draining Your Savings? New Study Reveals the Truth

Enrolling in the same Medicare Part D plan as your spouse can be convenient—but it can cost you. A 2025 study found couples often overpay by hundreds each year by not choosing plans tailored to their individual needs.

The ‘Social Default’ Costing You Money

A study published by the National Bureau of Economic Research in August found that many people enrolling in Medicare Part D resort to choosing the same plan as their spouse. This behavior is known as a “social default.”

“A social default is simply the act of doing what someone else is already doing,” said Tal Gross, a member of the study’s research team and a professor at Boston University’s Questrom School of Business.  “With Medicare Part D, going with the social default can be appealing because when you see a plan working for your spouse, then it can give a false illusion of reliability and trustworthiness, but Medicare is an individual-specific program with no acknowledgement for the household.”

The Cost of Copying Your Spouse

According to the study, a spouse who copies their partner’s Medicare Part D plan pays about $690 more per year, on average, than they would have if they’d chosen a plan based on their own prescription needs. In some cases, that extra cost can exceed $1,000, Gross said. 

“If you’re on a medication that costs more on your spouse’s plan, then you’ll pay more overall than if you’d selected the plan that is best for your prescription drug needs,” said Gross.

The best way to avoid overpaying is to choose a Medicare Part D plan based on your own prescription needs, not your spouse’s.

Tips for Smarter Medicare Plan Choices

Now that you know you shouldn’t automatically join the same plan as your spouse, how can you each find the most cost-effective plan for both your medical needs?

Use an online plan comparison tool. Gross advised utilizing online programs such as the Medicare Plan Finder to determine how much you might need to pay annually on each available Medicare Part D plan. “Put the prescriptions each person is taking into a computer (program) to tell you which plan out of three dozen or so available options will save you the most money,” he said. The program will estimate how much you’ll pay in total throughout the year under each plan.

Consider total annual costs. Part D plans charge more than the monthly premium. You also owe out-of-pocket when filling prescriptions. A higher premium plan may be the most cost-effective option when considering these other expenses. The Medicare.gov plan finder tool will show you all these costs.

Re-evaluate annually. Even if you’re happy with your current plan, don’t just renew by default. Insurers change their Part D plans every year. Your existing plan might increase costs, and better options could hit the market. Review your options each year during Part D Open Enrollment, which runs from Oct. 15 to Dec. 7.

Also, review your current prescriptions and consider any new medications you might need in the coming year. 

Reach out for help. Medicare has a free hotline to discuss your local plan options: 1-800-MEDICARE (1-800-633-4227). You could also see if your state has a State Health Insurance Program (SHIP) that you can call for advice. Another possibility is to meet with an insurance broker. They sell plans from multiple insurers and can help you determine the correct individual fit for you and your spouse.

The Bottom Line

You and your partner aren’t the same—your Medicare Part D plans shouldn’t be either. Choosing the same plan by default can cost couples hundreds each year. Use the Medicare plan finder to pick the most cost-effective option for each of you.