The Bone-Density Scan Is Free Every 24 Months. One Month Too Soon Can Make It Her Bill.

A 68-year-old woman on Original Medicare had a bone-density scan in September 2024. Her doctor had determined she was estrogen-deficient and at risk for osteoporosis, putting her inside one of Medicare’s qualifying groups. The scan was covered, and because the provider accepted assignment, she paid nothing.

Then the office schedules another scan for July 2026. It feels close enough to two years that nobody questions the date. At check-in, staff hand her an Advance Beneficiary Notice of Noncoverage (ABN) warning that Medicare may not pay. She signs with the rest of the paperwork. A few weeks later, Medicare denies the scan because it was performed too soon, and the imaging bill becomes hers.

The surprise is not that Medicare has a frequency rule. It is how that rule actually counts the months.

Medicare’s 24-Month Rule Is Not a 730-Day Stopwatch

Medicare Part B covers bone mass measurements once every 24 months for qualifying beneficiaries, or more often when medically necessary. When the provider accepts assignment, the covered test carries no deductible or coinsurance. But CMS defines the standard frequency more precisely: at least 23 months must have passed since the month in which the last bone mass measurement was performed.

That makes the calendar more forgiving than the draft originally assumed, but it still leaves a line. If her previous scan occurred in September 2024, a routine repeat in August 2026 can satisfy the standard frequency rule. July is different. Only 22 months have passed since the month of the previous test. One line on the appointment calendar can separate a $0 preventive service from a denied claim.

There Is a Legitimate Early-Scan Exception

Medicare can cover bone-density testing more frequently when it is medically necessary. CMS guidance specifically recognizes situations such as certain patients on long-term steroid therapy and follow-up testing used to assess response to approved osteoporosis treatment. Some Medicare coverage policies allow those medically necessary repeat measurements after 11 months have elapsed.

So an early appointment is not automatically wrong. What matters is why the physician ordered it and whether the documentation supports the exception. That is much different from moving a routine two-year follow-up forward because July happened to fit the office calendar better.

The ABN Is the Piece She Should Not Sign on Autopilot

An ABN is not just another consent form. Original Medicare providers use it when they expect Medicare may deny payment and want the patient to understand that she could become financially responsible. CMS describes the notice as a way to transfer potential liability to the beneficiary in certain circumstances.

That makes the form useful, not sinister. It gives her a chance to stop before the service happens. If the imaging center says the concern is frequency, she can ask for the date of the last Medicare-covered scan and reschedule if necessary. If the physician believes the earlier test is medically necessary, she can ask why and make sure the clinical reason is reflected in the order. Signing first and asking later gives away that opportunity.

Frequency denials are one of several Medicare traps that show up as unexpected bills rather than higher premiums, and we cataloged the rest in a free guide to Medicare’s hidden costs.

Check the Date Before the Scan

A bone-density appointment is easy to move. A denied claim is harder to unwind.

1. Find the month of the previous Medicare-covered bone mass measurement before scheduling the next routine scan. Do not rely on “about two years ago.”
2. If an ABN appears at check-in, ask exactly why Medicare may deny the test before signing it.
3. If the doctor wants the scan earlier for medical reasons, confirm that the order and medical record support the reason for testing more frequently.

The useful part of Medicare’s rule is that she does not actually have to count 730 days. She just has to know where Medicare drew the line before she lies down on the scanner.

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