Medicare Just Explained How It Denies Duplicate Lab Tests. The Denial Starts Before the Claim Exists.Medicare Just Explained How It Denies Duplicate Lab Tests. The Denial Starts Before the Claim Exists.

Last Thursday, CMS put out a short reminder in its weekly MLN Connects newsletter: Medicare doesn’t pay for duplicate lab tests unless they’re medically necessary. It ran four lines under a headline about labs, between a hospital PEPPER release and a Medicaid quality announcement.

Almost every practice that orders labs will read it as a lab problem. It isn’t one. The denial CMS describes is decided at the moment someone clicks “order.”

What the notice said vs. what happens at the MAC

The notice is about laboratory services. The denial lands on whoever ordered.

Here is the mechanism. CMS points to the Medicare Claims Processing Manual, Chapter 16. If you order a mix of panels and individual tests, you’re expected to know what’s inside each panel and not order individual tests that duplicate it (section 90.5). Your Medicare Administrative Contractor will deny duplicate tests that aren’t medically necessary (section 90.3). CMS’s example is a second vitamin D test.

When a repeat test is medically necessary, the notice says to use CPT modifier 91. CMS ties that modifier to its billing and coding article on repeat or duplicate services on the same day, so read that article before you build a rule around it.

Where the denial is actually made

Think about how a typical order gets built. A provider selects a panel from a favorites list. A standing order fires. A medical assistant adds “one more” individual test because the patient is already in the chair. The reference lab receives the order and bills what it was told to run.

No one in that chain is looking at the claim. The person who could prevent the denial is a clinician with a four-minute visit slot, and the person who sees the denial is a biller three weeks later. By then the specimen has been run and the lab has been paid or not paid. The practice’s ordering pattern hasn’t changed, so the next denial is already on its way.

Why this is a revenue cycle problem, not a lab problem

The clinical decision is rarely wrong. What goes wrong is the machinery around it:

• Panel contents are not mapped against individual test codes in the order catalog, so overlap is invisible at order entry.
• Nothing flags a repeat of the same test inside a short window, so the first sign is a denial.
• When a repeat is necessary, the medical necessity reason lives in a free-text note instead of a structured field that can trigger modifier 91.
• Denials from the reference lab and the practice’s own claims are never reconciled, so nobody sees the pattern by ordering provider.

None of this is hard to fix. It does have to be built into the workflow, and in most practices it is not. The pressure to fix it is also rising. The proposed CY 2027 conversion factors are $33.17 for qualifying APM participants and $32.84 for everyone else, both below the 2026 figures. When the rate is going down, every denied line comes straight out of margin.

The part nobody is saying out loud

The notice is a reminder. The signal is in the same sentence: CMS is exploring options in future rules.

The CY 2027 Physician Fee Schedule proposed rule includes a request for information on duplicate laboratory testing, imaging, and result sharing and interoperability. CMS’s framing is that results sit siloed inside the EHR that acquired them, so the next clinician doesn’t know they exist and orders them again. Comments closed September 14. The final rule normally arrives in early November.

Read those two things together. Medicare already denies duplicates based on what it can see. If result sharing improves, it will see more, and what you can see at the point of order will matter far more than it does today. A practice that can’t tell whether a result already exists will have its duplicates decided for it, claim by claim.

What to actually do with this

1. Pull 90 days of lab denials by ordering provider and by test. Duplicate-related denials will cluster. Find out whether they come from a handful of favorites-list panels or from standing orders.
2. Map your panels to their component tests. Do this once, in the order catalog, so that overlap is visible when the order is built rather than when the claim is denied.
3. Add a repeat-test alert. A same-test-within-a-window check at order entry costs far less than the denial it prevents.
4. Give modifier 91 a structured home. The reason a repeat is medically necessary should be a required field, not a sentence in the note. Have your coder confirm the same-day rule against the CMS article before you automate it.
5. Reconcile the reference lab’s billing with your own. If the lab is billing tests that your order intended as a panel, you need to know before the MAC does.
6. Decide who owns this. One person, one report, reviewed monthly. If duplicate denials belong to everyone, they belong to no one.

Also this week

Hospices: The election statement addendum is now mandatory for all elections starting October 1, 2026. It must be furnished in writing within 5 calendar days of the election effective date, and updates are due within 3 calendar days of a plan of care change. A valid signed addendum in the record is a condition of payment. CMS is using enforcement discretion through December 31, 2026, and MACs will not deny claims solely because the addendum is missing or incomplete during that window. That grace period ends on a fixed date, and any hospice without a tracked turnaround time by then will meet it as denials.

Acute Hospital Care at Home: If you bill telehealth for these patients, use POS 21 with modifier 95. Medicare treats them as inpatients even though the care is delivered at home.

Rural Health Transformation Program: CMS announced another round of state awards last week. Several fund remote patient monitoring, EHR upgrades, and cybersecurity at rural health centers. Billing teams at those sites should expect new workflows and new data arriving without a corresponding charge capture process.

A note on last week

Last week’s issue said the ACCESS Model’s FQHC and RHC eligibility began October 1, with claims on institutional 837I. That date has now passed. October 1 was also the day RHCs and FQHCs stopped billing telehealth under G2025 and began billing the individual CPT or HCPCS code with modifier 93 or 95. Two billing changes landed on the same day, so a clinic that checked only one of them may be building claims wrong right now.

CMS has also added the ACCESS Model to the 2027 Medicare & You handbook. Patients will begin asking about it, and the front desk should know what to say.

The 2030 view

For a long time, a denial was something that happened to a claim. A claim went out, a payer judged it, and the practice reacted.

The duplicate-testing RFI points the other way. Payers hold more data than practices do, and CMS is asking how to push that data out so that the decision to order is made with it. The more that happens, the earlier the revenue event moves. By 2030, the denial will be decided at order entry, and the revenue cycle will start with a clinician’s click, not with a charge.

A practice whose billing team only sees the claim will be correcting a decision that was made three weeks earlier by someone who never saw the rule.

If one of your providers ordered a panel and a duplicate individual test this morning, who would know before the claim went out?

One quiet plumbing problem a week: the CMS deadline, payer behaviour or code change that reaches your claims before it reaches the headlines. Written by Mihir Rajput, Founder & CEO of Medalyze Medtech.