17% on Medicare used drug discount sites. Those buys skip the Part D cap

17% of people on Medicare used a prescription drug discount website in the past 12 months. That is 1 in 6.

The number comes from the Commonwealth Fund’s 2025 Medicare Open Enrollment Survey of 4,018 people, reported in a blog post on Oct. 27. It was 19% in 2023.

The sites the Fund names are GoodRx, Cost Plus Drugs, BlinkRx, Amazon Pharmacy and TrumpRx. Some hand you a coupon for the pharmacy counter. Others mail the drug.

A lower price at the counter can cost more over the year. Here is why.

Who uses them

Use was higher in traditional Medicare than in Medicare Advantage, 21% to 14%, per the Fund. People in traditional Medicare with no Part D plan used the sites as often as people with one.

People with incomes under $25,000 a year were less likely to use the sites than people at every other income level.

Why people use them

Among people who used a site, the Fund reports these reasons:

• 57% said the price was lower than with their drug coverage.
• 28% said their plan didn’t cover the drug.
• 10% said the site was more convenient.
• 8% said they had no drug coverage at all.

Age changed the answers. A lower price was the reason for 59% of users 65 and older. It was the reason for 40% of users under 65, who have Medicare because of a disability. Users under 65 were more likely to say their plan didn’t cover the drug, 43% to 25%.

The cap catch

Part D has a yearly out of pocket cap on covered drugs. It is $2,100 in 2026 and $2,400 in 2027, per Medicare.gov and the CMS 2027 Rate Announcement.

Once your spending on covered drugs reaches the cap, you pay $0 for covered Part D drugs for the rest of the year. The cap applies in standalone drug plans and in Medicare Advantage plans with drug coverage.

A discount site purchase sits outside that count. Medicare.gov says TrumpRx and other discount cards aren’t creditable coverage. When you use one instead of your Medicare plan, the purchase doesn’t count toward your deductible or your out of pocket maximum.

So a cheaper price on one drug can leave you further from the cap. That matters most for people who fill expensive drugs and would hit the cap during the year. The Fund put it this way: “there could be higher financial costs over the long term.”

CMS allows one narrow exception during the deductible, and only if you send your plan the receipt. We covered it in our Epic cash price story.

The penalty for skipping Part D

Some people use the sites in place of a drug plan. Medicare.gov says doctor samples, discount cards, free clinics and drug discount websites aren’t drug coverage.

The rule is in Medicare.gov’s penalty guide. It starts after your Initial Enrollment Period ends. A gap of 63 days or more in a row without Medicare drug coverage or other creditable coverage can bring a Part D late enrollment penalty.

Medicare.gov says the penalty is permanently added to your premium. You generally pay it for as long as you have Medicare drug coverage, even if you switch plans.

The math is 1% of the national base beneficiary premium for each full month you went without coverage. That base is $38.99 in 2026.

Medicare.gov’s example is a person who waited 14 months and owes a 14% penalty. At the 2026 base, that is about $5.50 a month on top of the plan premium. The base can rise each year, and the penalty rises with it.

People who get Extra Help don’t pay the penalty.

What to do before Dec. 7

Open enrollment runs Oct. 15 to Dec. 7, per Medicare.gov.

1. List the drugs you buy on discount sites. Check if a 2027 plan covers them.
2. Ask the pharmacy for two prices on each drug, your plan’s price and the discount price. Medicare.gov tells members to make that comparison.
3. If you expect to reach the cap, add up the whole year, not one fill. Under the Medicare.gov rule, dollars spent through the plan move you toward the $2,400 cap in 2027. Discount dollars don’t.
4. If you skip Part D because your drugs are cheap now, price a low premium plan first. Medicare.gov suggests one to avoid the penalty.
5. If money is tight, check Extra Help. It lowers drug costs and removes the penalty.

Our Medicare open enrollment 2027 guide lists the other Part D changes for next year.