What is the Medicare laboratory 14-Day Rule?

It is part of Medicare's laboratory date-of-service (DOS) policy at 42 CFR 414.510. As a general rule, the DOS for a clinical diagnostic lab test is the date the specimen was collected. When a specimen is collected during a hospital encounter and the test is ordered less than 14 days after the patient is discharged, the test is generally treated as a hospital service that the hospital bills, and the performing lab must seek payment from the hospital rather than from Medicare. If the physician orders the test 14 or more days after discharge, the DOS becomes the date the test is performed and the performing lab can bill Medicare directly.

What is the molecular / ADLT exception to the 14-Day Rule?

In the CY 2018 OPPS final rule, effective January 1, 2018, CMS created an exception for Advanced Diagnostic Laboratory Tests (ADLTs) and molecular pathology tests that are excluded from OPPS packaging. Under the exception, the DOS is the date the test is performed, and the performing laboratory bills Medicare directly under the Clinical Laboratory Fee Schedule, when the test is performed after a hospital outpatient is discharged, the specimen was collected during a hospital outpatient encounter, the results do not guide treatment during that encounter, and the test is reasonable and medically necessary. The exception applies to hospital outpatient specimens, not inpatient specimens.

Does the exception apply to inpatient specimens?

No. The 2018 molecular/ADLT exception applies to specimens collected from a hospital outpatient. Tests on inpatient specimens are handled under separate bundling rules and are generally billed through the hospital. You should confirm the specifics of any given scenario against current CMS DOS guidance and your Medicare Administrative Contractor's policy.

Why does the 14-Day Rule cause revenue leakage?

Because the rule decides who has the right to bill and when, a mismatch can mean the performing lab bills Medicare when it should have billed the hospital, or fails to bill Medicare when it had the right to. Either path can produce denials, recoupments, or unpaid work, and recent False Claims Act enforcement shows the compliance stakes of getting the timing and the billing party wrong.

The 14-Day Rule, Plain English: Who Bills Medicare for a Molecular Test, and When

A specimen leaves a hospital outpatient clinic on a Tuesday. A patient came in, blood was drawn or a tissue block was pulled, and the physician decided that a molecular panel was warranted to guide what comes next. The patient goes home. Three days later the order reaches your reference lab, you run a complex molecular assay, you produce a report, and you send a bill. The clinical part went perfectly. Now answer one deceptively simple question: who is supposed to receive that bill, you or the hospital, and as of what date?

That question is the entire substance of Medicare's laboratory date-of-service policy, the rule the industry has long called the "14-Day Rule." It does not decide whether a test is covered or medically necessary. It decides something more basic and more easily fumbled: which party holds the right to bill Medicare, and on what date the service is considered to have occurred. Get it wrong in one direction and you bill Medicare for a service you had no standing to bill. Get it wrong in the other and you do unpaid work while the hospital never pays you either. This article walks through the rule in plain language, with the molecular and ADLT exception that changed the landscape in 2018, and why it remains one of the quieter sources of revenue leakage for labs that handle hospital-outpatient specimens.

Disclaimer: This article is educational and is not medical, legal, or billing advice. It is not a coverage or payment determination for any specific test, specimen, or claim. Medicare policies change, Medicare Administrative Contractors apply local rules, and the only authoritative sources are the current regulation, CMS guidance, and your contractor's policy. Always verify against current CMS date-of-service guidance and consult qualified billing, coding, compliance, and legal professionals before acting. Use this information at your own risk.

The default rule: date of service equals date of collection

Start with the baseline, because the exceptions only make sense against it. Under Medicare's laboratory date-of-service policy, codified at 42 CFR 414.510, the date of service (DOS) for a clinical diagnostic laboratory test is generally the date the specimen was collected. That single default carries surprising weight, because the date of service is tied to the encounter, and the encounter determines who bills.

When a specimen is collected during a hospital encounter, the test tends to be treated as part of that hospital service rather than as a freestanding lab service. In practical terms, the hospital bills Medicare for the encounter and its associated services, and the performing laboratory, if it is a separate reference or molecular lab, looks to the hospital for payment rather than to Medicare. This is the bundling logic that sits underneath everything else here. (CMS, Laboratory Date of Service Policy)

Where the "14 days" comes from

The "14-Day Rule" nickname describes the hinge in that default. The general policy is that the DOS is the date of specimen collection unless the ordering physician orders the test at least 14 days after the patient is discharged from the hospital. If the order comes 14 or more days after discharge, the date of service shifts to the date the test was actually performed, the test is effectively unbundled from the hospital encounter, and the performing laboratory bills Medicare directly under the Clinical Laboratory Fee Schedule (CLFS). (CMS; Houston Harbaugh)

So the 14-day window is really a timing test that flips the billing party. Inside the window, with the date of service pinned to collection, the test rides with the hospital encounter, and the lab seeks payment from the hospital. Outside the window, the lab can go straight to Medicare. The rule did not start as a molecular-testing rule at all. It traces back to the mid-2000s and was initially shaped around chemosensitivity testing on tumor samples, which became effective for the 2007 calendar year, where fresh tissue was required and results rarely affected an inpatient's immediate treatment. (Discoveries in Health Policy) The mechanics were built for a different era of testing, and that mismatch is exactly what created problems once molecular medicine arrived.

Why molecular labs hit a wall before 2018

Here is the practical bind that the original framework created. Modern molecular pathology and advanced diagnostic testing is frequently ordered soon after a patient is seen, not two weeks later. A physician sees a patient, decides a complex genomic assay is warranted, and orders it promptly. Under the default rule, a specimen collected during a hospital outpatient encounter with the order arriving inside the 14-day window meant the test was treated as a hospital service.

Before 2018, that left reference and independent laboratories unable to bill Medicare directly for many molecular pathology tests ordered less than 14 days after a hospital outpatient discharge. Instead, the lab had to seek reimbursement from the hospital, and the hospital billed Medicare. (APS Medical Billing) That arrangement was awkward for everyone. Hospitals were billing for sophisticated send-out tests they did not perform and could not always price, labs were dependent on hospital payment for highly specialized work, and patients and physicians sometimes waited or maneuvered around the calendar. Stakeholders argued the rule was throttling access to precision medicine. (GenomeWeb)

The 2018 exception that changed who bills

CMS responded in the CY 2018 Hospital Outpatient Prospective Payment System (OPPS) final rule, published December 14, 2017, by creating an exception to the laboratory date-of-service policy. Effective January 1, 2018, for Advanced Diagnostic Laboratory Tests (ADLTs) and molecular pathology tests that are excluded from OPPS packaging, the date of service is the date the test was performed, rather than the date of collection, when specific conditions are met. (CMS; Quadax)

The effect is the part to internalize. When the exception applies, the performing laboratory bills Medicare directly under the CLFS for those tests, even when they were ordered within 14 days of a hospital outpatient discharge. (APS Medical Billing) The molecular or genomic lab that actually ran the assay is the party that bills, instead of routing the work through the hospital. That is a meaningful shift in standing, and it only holds when the conditions below are satisfied.

The conditions, stated precisely

The exception is conditional, and the conditions matter because missing any one of them can put you back on the wrong side of the billing line. As CMS and Medicare Administrative Contractor guidance describe it, the molecular pathology and ADLT exception for hospital outpatient specimens applies when:

The test is performed following the hospital outpatient's discharge from the hospital outpatient department.
The specimen was collected from a hospital outpatient during an encounter.
It was medically appropriate to have collected the sample during that hospital outpatient encounter.
The results do not guide treatment provided during that hospital outpatient encounter.
The test was reasonable and medically necessary for the treatment of an illness.

(CMS; Noridian, Laboratory Date of Service — ADLT and Molecular Pathology Tests)

Two qualifiers deserve emphasis. First, the exception is for outpatient specimens. It does not extend to specimens collected from a hospital inpatient; inpatient testing is handled under separate bundling rules and generally flows through the hospital. (CMS) Second, the "results do not guide treatment during the encounter" condition is doing real work. If the molecular result was meant to direct care during that same outpatient encounter, the logic of the exception, which assumes the test informs later management, no longer fits, and you should treat the billing question as unresolved until you confirm the specifics.

It is also worth knowing what an ADLT is, since the term carries weight in this rule. CMS generally describes an ADLT as a test furnished by a single laboratory that analyzes multiple biomarkers (such as DNA, RNA, or proteins) and, through a unique algorithm, yields new clinical diagnostic information that cannot be obtained from any other test or combination of tests, or a test that is cleared or approved by the FDA, among other criteria. (GenomeWeb) The distinction matters because ADLTs and molecular pathology tests excluded from OPPS packaging are the categories the 2018 exception was built around.

A note on storage, and on the inpatient line

A couple of adjacent rules tend to surface in the same conversations, and they are easy to trip on. Medicare's DOS policy also addresses archived specimens: if a specimen is stored more than 30 calendar days before testing, it is generally considered to have been archived, and the date of service becomes the date the specimen was obtained from storage rather than the date of original collection. (CMS) That can independently change the analysis for tests run long after collection.

And the inpatient line is its own world. The bundling rules for inpatient specimens are distinct, the molecular/ADLT outpatient exception does not reach them, and conflating the two is a common way that otherwise careful billing operations get the party wrong. When you are unsure whether a specimen counts as inpatient or outpatient for these purposes, that ambiguity is itself a reason to slow down and verify, not to assume.

Where the money leaks

None of this is academic. The 14-Day Rule decides who bills, and a rule that decides who bills is a rule that decides who gets paid and who eats the cost when the answer is wrong.

The leakage runs in both directions. In one direction, a lab bills Medicare directly for a test that should have been billed by the hospital because the conditions for the exception were not actually met. That is not just a denied claim, it is a compliance exposure. In January 2025, reporting described a False Claims Act settlement in which a laboratory and health system resolved allegations, for roughly $388,667, that physician orders for certain lab testing were delayed until 14 days after discharge specifically to sidestep the bundling rule. (Hall Render) Whatever the specifics of that matter, the signal for operators is clear: timing the order to manufacture a billing right is the kind of thing the government pursues, and the DOS policy is being actively enforced.

In the other direction, a lab that is genuinely entitled to bill Medicare under the 2018 exception sometimes fails to, or routes the work through a hospital arrangement that pays slowly or incompletely, simply because the staff applying the rule did not realize the exception applied. That is quieter leakage, but it is leakage all the same: real molecular work performed, with payment left on the table or trapped in a hospital pass-through. The performing lab had standing to bill Medicare directly and did not use it.

What makes this category so slippery is that the right answer depends on a stack of moving facts: the specimen setting, the specific test type and its OPPS-packaging status, the discharge timing, whether results drove same-encounter care, and whatever your Medicare Administrative Contractor currently says. Each of those can change, and CMS has revisited the DOS policy more than once. A rule you "know" from 2019 is not necessarily the rule today.

Confirm before you bill

If you operate a molecular or genetic-testing lab, or an oncology practice that sends specimens out, the disciplined move is to treat the billing-party decision as its own checkpoint, not an afterthought to the clinical result. Identify the specimen setting, confirm the test category and its packaging status, walk the timing and the same-encounter-treatment condition, and only then decide whether you bill Medicare directly or look to the hospital. And because this is technical billing policy that genuinely changes, confirm the specifics of any uncertain case against current CMS date-of-service guidance and your MAC's published policy rather than relying on institutional memory.

This is precisely the kind of payer and CMS logic that quietly goes stale. Date-of-service rules, packaging exclusions, ADLT determinations, and contractor guidance are constantly maintained documents, and the gap between what a rule said two years ago and what it says now is exactly where labs lose money or take on risk without noticing. Keeping that logic current, so the billing decision reflects today's policy rather than yesterday's, is the category Converus works in. The clinical work is hard enough; the rule about who gets paid for it should not be the part that leaks.