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Does Medicare Cover Mammograms? The Diagnostic Imaging Bill South Dakota Should Know About in 2026

The screening mammogram is genuinely free. The second picture the radiologist takes in the same appointment often isn't — and Medicare has never fixed that the way it just fixed it for people under 65.

Big Sioux Benefits Data Desk

Published September 8, 2026 · 15 min read · Sourced from CMS.gov, Medicare.gov, and ACS CAN

If your "free" annual mammogram came back with a bill attached, you didn't do anything wrong — Medicare split your visit into two different services with two different price tags, and nothing in the exam room was required to warn you. Screening mammograms are genuinely $0 under Medicare. Diagnostic mammograms — the second look, the extra view, the callback after something on the first picture caught a radiologist's eye — are billed as a medical service, with the standard 20% Part B coinsurance attached. This guide walks through why that split exists, what it actually costs in South Dakota in 2026, the real federal fix that just arrived for people under 65 and quietly skipped Medicare, and how Medigap or Medicare Advantage change what you owe.

Every figure below comes from a primary source pulled this week: Medicare.gov's own mammogram coverage page, CMS National Coverage Determination 220.4, the CMS 2026 Parts A & B cost-sharing fact sheet, ACS CAN's own 2018–2023 claims analysis, and NCI's State Cancer Profiles for South Dakota. No invented numbers, and no "call for pricing."

Why your mammogram can turn into two different bills

Medicare has treated mammography as two separate services since its National Coverage Determination on the subject, first issued in 1978 and never substantially rewritten, per CMS NCD 220.4. A screening mammogram is preventive: a routine check on someone with no symptoms, meant to catch a problem before it announces itself. A diagnostic mammogram investigates something specific — a lump you or your doctor found, breast pain, nipple discharge, a personal history of breast cancer, or a callback because your screening picture showed something worth a closer look.

Those are two different Medicare benefit categories, and Medicare prices them completely differently. Screening mammography is covered at 100% — you pay nothing, per Medicare.gov — once every 12 months for women 40 and older, with one baseline screening allowed between ages 35 and 39 under the NCD's own rule. Diagnostic mammography is billed like any other Part B medical service: you owe the standard coinsurance once your deductible is met.

The part that catches people off guard: the reclassification can happen mid-visit. If a radiologist looks at your screening images and wants extra views of one area right there in the same appointment, that portion of the visit can be billed as diagnostic — even though you walked in for what you thought was your free annual check. Nobody hands you a form asking permission first, because the decision is clinical, not administrative. You find out when the statement arrives.

Source: Medicare.gov — Mammograms & CMS National Coverage Determination 220.4 — Mammography, 2026 plan year.

What a diagnostic mammogram actually costs in 2026

The math itself is simple, even if the moment it lands on you isn't. Once you've met the 2026 Part B deductible of $283 — the same deductible that applies to every other Part B service you use all year, not a separate mammogram-only deductible — you owe 20% of the Medicare-approved amount for a diagnostic mammogram, per the CMS 2026 Parts A & B cost-sharing fact sheet. The exact dollar figure depends on the specific imaging code and where you're seen, since Medicare's approved amount for radiology varies by procedure. The honest advice: ask your imaging center for the Medicare-approved amount for your specific exam before your appointment, so you know the number before the bill does.

If your diagnostic mammogram leads to a follow-up ultrasound, MRI, or biopsy, each of those carries its own separate 20% coinsurance on top. None of it counts against the Part D drug cost cap, because none of it is a drug — it's Part B medical imaging, and Original Medicare's 20% coinsurance has no annual ceiling of its own unless you have Medigap or a Medicare Advantage plan's out-of-pocket maximum standing behind you.

Source: Medicare.gov & CMS 2026 Parts A & B cost-sharing fact sheet.

How much this adds up to for people who don't have Medicare yet

It helps to see what this looks like for a working-age person, because it shows how real the cost barrier actually is — and because a lot of Big Sioux Benefits readers are the adult children of someone on Medicare, still on a private plan themselves. The American Cancer Society Cancer Action Network (ACS CAN) analyzed millions of real insurance claims and found that 70.4% of privately insured patients paid something out of pocket for follow-up breast diagnostic testing in 2023, with the typical payment running $169.27 — up 75% from $96.56 in 2018, per ACS CAN's own claims analysis. For a diagnostic mammogram specifically, the average out-of-pocket cost rose 73%, from $83.71 in 2018-2019 to $144.84 in 2023. (If you're under 65 and uninsured or underinsured, South Dakota runs its own no-cost program for women 40 to 64 called All Women Count!, through the state Department of Health — worth knowing about for yourself or someone you're helping who hasn't reached Medicare age yet.)

ACS CAN also modeled what this looks like for Medicare beneficiaries specifically, using a 20% Part B coinsurance assumption applied against Medicare's typically lower approved payment rates. Their finding: out-of-pocket cost sharing for these same follow-up tests grew more slowly for Medicare patients than for commercially insured ones, but it still grew — a range of 6.5% (for MRI) to 30.2% (for biopsy) between 2018-2019 and 2023, per the same ACS CAN analysis. The direction is the same even where the pace differs: this bill has been getting bigger, not smaller, for years.

The reason any of this matters beyond a single unwelcome bill: ACS CAN's modeling found that people facing out-of-pocket costs for follow-up testing were measurably less likely to get that testing done quickly, and less likely to come back for their next screening mammogram at all. Nationally, the analysis estimates 1.1 million women delay a necessary follow-up test each year because of the out-of-pocket cost, and roughly 378,000 more women skip their next year's screening mammogram entirely out of fear of another surprise bill, per ACS CAN's own simulation. In their model, patients who faced cost-sharing were diagnosed at a later stage more often than patients who faced none — 37.7% versus 33.7% — and later-stage breast cancer costs more to treat and is harder to survive. None of that model was built on Medicare claims specifically, but the underlying mechanism — a bill that makes people hesitate — doesn't stop applying just because someone turned 65.

Why South Dakota carries more of this bill than almost anywhere else

Here's the number that makes this a South Dakota story and not just a national one. Averaged across every kind of follow-up breast imaging and biopsy, patients in South Dakota paid 48.6% of the total bill out of their own pocket between 2018 and 2023 — the 2nd-highest share of any state in the country, behind only North Dakota, per ACS CAN's state-by-state analysis. Compare that to Delaware, at the low end, where patients covered just 9.0% of the bill themselves.

Top five states by average out-of-pocket cost share for breast cancer follow-up imaging, 2018–2023. Source: ACS CAN — Out-of-Pocket Costs for Breast Cancer Follow-Up Testing (Jan. 2025).

That gap isn't about how sick South Dakota is. The state's own cancer numbers actually run close to, or better than, the national average: South Dakota's female breast cancer incidence rate is 132.0 per 100,000 (2018–2022) against a U.S. rate of 131.3, its breast cancer mortality rate is 17.3 per 100,000 (2019–2023) against a U.S. rate of 19.2, and its share of cases caught at a late stage — 30.3% — sits slightly below the national 31.0%, per NCI's State Cancer Profiles. What's different here isn't the disease. It's who ends up holding the bill once a screening finds something worth a second look — a pattern researchers have tied to plan design, provider pricing, and how much of the state's insured population sits in high-deductible plans, not to how sick people are.

South Dakota also screens slightly below the national pace to begin with: 70.8% of women 40 to 74 reported a mammogram in the past two years as of 2024, against a national rate of 74.5%, per America's Health Rankings, built on CDC survey data. A cost scare after the first callback is one plausible reason some people don't come back for the next one.

The fix that just arrived for people under 65 — and quietly skipped Medicare

This part is genuinely new, and it's the reason this is worth writing about now. On December 30, 2024, the Health Resources and Services Administration (HRSA) updated its Women's Preventive Services Guidelines to add two new sentences: when a screening mammogram needs additional imaging to complete the process — extra views, an ultrasound, an MRI — that additional imaging is now part of the recommended preventive service, not a separate diagnostic add-on. Starting with plan years beginning on or after December 20, 2025 — in practice, 2026 for most calendar-year plans — most non-grandfathered group health plans and ACA-marketplace plans have to cover that additional imaging at $0, per reporting from the American College of Radiology and Mercer's own employee-benefits analysis.

Read that again: for most people under 65 on an employer plan or an ACA marketplace plan, the exact problem this article opened with — a "free" mammogram that turns into a bill the moment a radiologist wants a second look — is being fixed starting this year. It is not being fixed for Medicare. The HRSA update runs through the Affordable Care Act's preventive-services mandate, a legal mechanism that has never applied to Medicare, which still runs on CMS NCD 220.4 from 1978. Nothing about that determination changed alongside the HRSA update, and nothing in the HRSA rule itself mentions Medicare or Medicare Advantage.

There is a bill aimed specifically at closing this gap more broadly: the Find It Early Act, reintroduced in Congress on November 20, 2025 by Rep. Rosa DeLauro (D-CT) and Rep. Brian Fitzpatrick (R-PA), which would require health plans to cover screening and diagnostic breast imaging — mammograms, ultrasounds, MRIs — without cost-sharing, per Rep. DeLauro's own announcement. As of this writing it remains a bill, not a law, and its current text is written around "health insurance plans" broadly rather than Medicare specifically. Until something like it passes and Medicare's own coverage rule is rewritten, the 20% diagnostic coinsurance stands.

Dense breast tissue and the mammogram you might need next

There's a second, related change worth knowing about. Since a federal rule took full effect in 2024, every mammography facility in the country has to tell you, in writing, whether your breast tissue is classified as dense — because dense tissue can hide a tumor on a standard mammogram, and dense tissue is itself an independent risk factor for breast cancer, per the FDA's own press release on the rule. Roughly half of women over 40 have dense breast tissue, according to the same FDA release.

Getting that notice doesn't automatically trigger extra coverage. Medicare doesn't add a supplemental ultrasound or MRI to your benefits just because your report says "dense" — your doctor has to order supplemental imaging as medically necessary based on your specific risk, and when they do, it's typically billed as diagnostic, with the same 20% coinsurance discussed above. The notice is valuable information. It is not, on its own, a coverage change. If your report says you have dense breasts, that's worth a real conversation with your doctor about your personal risk factors and whether additional imaging makes sense for you — not just a form letter to file away.

How to read your own bill: the modifier that explains the switch

If you want to check, for yourself, whether your visit really was reclassified from screening to diagnostic, there's a specific code to look for. When a screening mammogram turns diagnostic on the same day — the radiologist sees something and orders extra views right then — the diagnostic claim is billed with a tracking code called modifier GG, attached specifically to flag that a screening and a diagnostic mammogram happened for the same patient on the same day, per CMS's own mammography billing transmittal. It exists so Medicare's claims system knows the diagnostic charge grew out of that day's screening visit rather than a separate appointment.

You won't usually see "GG" printed on a patient-facing statement, but you can ask your imaging center's billing office directly whether that modifier was used on your claim, and you can look for both a screening and a diagnostic line item on your Medicare Summary Notice for the same date of service. If the diagnostic portion happened on a completely different day than your screening, GG doesn't apply — that diagnostic claim stands on its own the same way it would for any other doctor-ordered exam.

A worked example: the same mammogram, two different months

Timing changes what you actually pay, because the Part B deductible resets every January 1 and applies once per year across every Part B service you use — not per procedure. Here's how the same diagnostic mammogram plays out depending on when in the year it happens:

Illustrative example using the 2026 Part B deductible and coinsurance rate. Source: CMS 2025 Medicare Parts A & B Premiums and Deductibles (Fact Sheet). The $200 figure is a placeholder for illustration — ask your own imaging center for the Medicare-approved amount on your specific exam.

That's the same exam, the same coinsurance rate, and a bill that can look very different depending on the calendar. It's also why the "how much has your deductible already absorbed this year" question in the five-step method above is worth asking before you assume the worst — or the best.

If you're the one reading the bill for a parent

A lot of the people who read this site aren't on Medicare themselves — they're the adult child sorting through a parent's mail. If that's you, a few things are worth knowing specifically for this situation. Your parent's Medicare Summary Notice (mailed quarterly, or viewable anytime at Medicare.gov with their account) lists every claim by date, including whether a mammogram was billed as screening or diagnostic, and shows exactly what Medicare paid versus what your parent owes. If a bill from the imaging center arrives before the Medicare Summary Notice does, it's reasonable to wait and compare the two rather than paying immediately — billing offices do make coding errors, and a corrected claim can change what's actually owed. And if your parent has Medigap Plan G, a diagnostic-mammogram bill for anything beyond the Part B deductible is very likely a mistake worth a phone call, since Plan G is supposed to absorb that 20% automatically.

How Medigap and Medicare Advantage change what you actually owe

This is where your choice of coverage stops being abstract and starts deciding your actual bill. The two paths handle diagnostic imaging in genuinely different ways.

Source: CMS — Choosing a Medigap Policy (Publication 02110), CMS standardized Medigap benefits.

Medigap Plan G pays your Part B coinsurance in full — on a diagnostic mammogram, a follow-up ultrasound, a biopsy, anything billed under Part B — leaving you responsible only for the annual Part B deductible. Plan N also covers Part B coinsurance but can carry a small copay for some office and ER visits; it doesn't apply to imaging cost-sharing itself. Plans K and L cover only a percentage of that coinsurance, with an annual out-of-pocket cap of their own ($7,220 for Plan K, $3,610 for Plan L).

A Medicare Advantage plan takes a different shape entirely. Screening mammograms stay at $0 by federal rule — Advantage plans cannot charge any deductible, copayment, or coinsurance for an in-network Medicare-covered preventive service, per 42 CFR § 422.100(k). Diagnostic imaging isn't a preventive service, so your specific plan sets its own copay or coinsurance for it — but whatever you owe counts toward your plan's annual out-of-pocket maximum, a real ceiling Original Medicare alone does not have. Which structure fits you better depends on how much you value a predictable monthly premium (Medigap) versus a lower premium with a capped worst case (Advantage) — a genuinely personal call, not a one-size answer.

The Sioux Falls-area Medicare Advantage plan landscape

If you're weighing Medicare Advantage against Medigap partly because of how each handles a scenario like this, here's the real 2026 roster for Minnehaha County — 39,532 Medicare beneficiaries, 5 carriers, and 11 Part C plans in total. These are the five standard PPOs open to anyone with Medicare in the county:

Source: CMS Medicare Advantage / Part D Landscape (PY2026), Minnehaha County, 2026 plan year.

Every one of these plans is required to cover your screening mammogram at $0 in-network. What differs between them — and what's worth asking about directly, since it isn't published the way premiums are — is the copay or coinsurance each plan applies to diagnostic imaging, and where that falls within its annual out-of-pocket maximum. That's a conversation worth having before you need it, not after.

A five-step method to protect yourself before your next mammogram

You don't need to become a billing expert to get ahead of this. Here's the method, and you can absolutely run it yourself.

1. Ask your doctor, before the appointment, whether it's a screening or a diagnostic order. If you have a symptom, a lump, or a prior abnormal result, it's very likely diagnostic — ask directly so you're not guessing after the fact.
2. Ask the imaging center for the CPT billing code and the Medicare-approved amount before you go in, especially if you know you're being seen for a follow-up rather than a routine annual check.
3. If the radiologist wants extra views during a screening visit, ask on the spot whether that changes the billing. You can ask the technologist or front desk directly; you're allowed to ask before you leave the building.
4. Check whether you've met your Part B deductible for the year — you can see this on your Medicare Summary Notice or through your Medicare.gov account, and it tells you instantly whether a diagnostic bill will be the full 20% or your remaining deductible plus 20%.
5. Know which coverage is standing behind you — Medigap Plan G closes this gap entirely; a Medicare Advantage plan caps it at your annual out-of-pocket maximum. If you don't know which applies to your situation, that's worth a real conversation, not a guess.

How we help

This is exactly the kind of question a local, independent advisor exists to answer — not to sell you something, but to sit down with your specific Medigap or Medicare Advantage plan and tell you, in plain terms, what a diagnostic mammogram or a follow-up ultrasound would actually cost you under your coverage, and whether a different structure would protect you better going forward. We're a licensed independent agency based in Sioux Falls, and we compare the plans we offer in the Sioux Falls and Siouxland area against your real situation — your doctors, your health history, your budget. There's no cost to talk, because carriers pay the agent, not you.

What to watch heading into the 2026 Annual Enrollment Period

1. Whether the Find It Early Act moves in Congress. If it becomes law, it could eventually close this exact gap for Medicare — but that hasn't happened yet, and nothing about your 2026 coverage should assume it will.
2. Your own dense-breast notification, if you get one. Read it, and bring it up with your doctor rather than filing it away.
3. Whether your current Medigap or Advantage plan actually closes this gap the way you think it does — worth confirming before you need it, not during a stressful callback appointment.
4. Your Part B deductible status each year. A diagnostic mammogram early in the year, before you've met the $283 deductible, costs more out of pocket than the same exam in November.
5. Whether CMS revisits NCD 220.4 itself. It hasn't moved in decades, but the HRSA update on the private-plan side shows the underlying medical guidance has evolved — Medicare's own rule may eventually follow.

How we know all this: Big Sioux Benefits runs every article through a data desk that cross-references CMS coverage determinations, CMS's own Part A & B cost-sharing fact sheets, the CMS PY2026 Medicare Advantage plan landscape, and outside research from the American Cancer Society Cancer Action Network and the National Cancer Institute, built by Strategic AI Architects. Every figure here is from a source fetched and verified this week, listed above and linked inline. This is education, not medical or legal advice; confirm your own coverage, costs, and eligibility with a licensed agent, your doctor, or Medicare.gov. We take no payment from any carrier to feature a plan.