Prothrombin Time (PT) — NCD 80 | CMS Coverage Update

TL;DR: The Centers for Medicare & Medicaid Services modified NCD 80 governing prothrombin time (PT) testing, with an effective date of March 7, 2026. Here's what billing teams need to do.

This update to the CMS prothrombin time coverage policy clarifies when PT and PT/INR testing is covered under Medicare, tightens documentation requirements for specific patient populations, and sets frequency limits that will trigger claim denial if ignored. The policy does not list specific CPT codes, but PT testing is billed under standard coagulation lab codes your team already uses — the coverage criteria and medical necessity documentation requirements are where this update bites.

CMS Prothrombin Time Coverage Criteria and Medical Necessity Requirements 2026

The CMS prothrombin time coverage policy covers PT testing under four distinct clinical indications. Each one has real specificity — this isn't a blanket "order when needed" policy. Your billing team and ordering providers both need to understand the criteria, because medical necessity documentation is the first thing a MAC auditor checks on coagulation testing claims.

Indication 1: Warfarin monitoring. PT/INR is covered to monitor and regulate warfarin dosing. This is the highest-volume use case. The policy is explicit that PT is generally not useful for monitoring patients on heparin who are not also taking warfarin. If your providers order PT on heparin-only patients, those claims are at risk.

Indication 2: Signs or symptoms of abnormal bleeding or thrombosis. Covered examples include swollen extremity with or without prior trauma, unexplained bruising, abnormal bleeding or hemorrhage, hematoma, and petechiae or other signs of thrombocytopenia that could indicate disseminated intravascular coagulation (DIC). The clinical finding must be documented in the chart — "rule out bleeding disorder" without a documented symptom does not meet this standard.

Indication 3: History of conditions associated with bleeding or thrombosis risk via the extrinsic coagulation pathway. This is the longest and most consequential indications list in the policy. Covered conditions include dysfibrinogenemia, afibrinogenemia, acute or chronic liver dysfunction or failure (including Wilson's disease and hemochromatosis), DIC, congenital and acquired deficiencies of factors II, V, VII, and X, vitamin K deficiency, lupus erythematosus, hypercoagulable state, paraproteinemia, lymphoma, amyloidosis, acute and chronic leukemias, plasma cell dyscrasia, HIV infection, malignant neoplasms, hemorrhagic fever, salicylate poisoning, obstructive jaundice, intestinal fistula, malabsorption syndrome, colitis, chronic diarrhea, peripheral venous or arterial thrombosis, pulmonary emboli, myocardial infarction, organ transplantation, and the presence of circulating coagulation inhibitors.

That list matters for diagnosis coding. If you're billing PT testing for a patient with any of those conditions, the relevant diagnosis must be on the claim and documented in the chart.

Indication 4: Pre-procedure hemorrhage/thrombosis risk assessment. PT is covered to assess risk before invasive procedures or operations in patients with a personal history of bleeding or a condition associated with coagulopathy, and prior to the use of thrombolytic medication. Routine pre-op PT on a patient with no bleeding history or coagulopathy risk is not covered. That's a common denial driver — audit your pre-op order sets now.

One important nuance: the policy states that current medical information does not clarify the role of laboratory PT testing in patients who are self-monitoring their PT at home. The indications for covered testing apply regardless of whether the patient is also doing PT self-testing. Don't deny or reduce testing frequency just because a patient has a home INR device — and don't assume home self-monitoring eliminates the need for lab-based PT claims.

CMS Prothrombin Time Exclusions and Non-Covered Indications

The policy identifies several situations where PT testing is not covered or where prior authorization-level documentation is required before reimbursement.

Heparin-only patients. PT is not useful for monitoring patients on heparin who are not also taking warfarin. Claims for PT on heparin-only patients will not meet medical necessity under this policy. Use PTT (partial thromboplastin time) instead — that's the appropriate test for intrinsic pathway assessment in heparin management.

Stable warfarin patients tested too frequently. The policy is direct: in a patient on stable warfarin therapy, it is ordinarily not necessary to retest frequently. The policy text was truncated in the source document at this point, but the implication for prothrombin time billing is clear — high-frequency testing on a stable patient without documented clinical justification (dose change, new interacting medication, intercurrent illness) will draw scrutiny.

ESRD patients tested more than weekly. This is the most operationally specific limitation in the policy. When an ESRD patient is tested for PT more than once per week, you must document medical necessity beyond chronic renal failure or renal failure unspecified. "CKD stage 5" or "ESRD" alone does not justify weekly-plus PT testing. You need a documented clinical reason — an acute change, a dose adjustment, a bleeding event — that goes beyond the baseline ESRD diagnosis.

Coverage Indications at a Glance

CMS Prothrombin Time Billing Guidelines and Action Items 2026

The billing guidelines for PT testing under NCD 80 are more documentation-intensive than most labs realize. Here are the specific actions your team needs to take before March 7, 2026.

If your practice has a high volume of ESRD patients or runs an anticoagulation clinic, loop in your compliance officer before the effective date of March 7, 2026. The frequency limitation for ESRD patients is specific enough that an internal audit now will save you from a MAC probe later.

CPT, HCPCS, and ICD-10 Codes for Prothrombin Time Under NCD 80

CPT and HCPCS Codes

NCD 80 does not specify CPT or HCPCS codes. The policy governs when PT testing is covered, not which billing code to use. Contact your MAC or refer to your payer's fee schedule for the applicable billing codes in your region. Your MAC may also have a local coverage determination (LCD) that supplements NCD 80 with specific code guidance.

ICD-10-CM Diagnosis Codes

NCD 80 does not list specific ICD-10-CM codes. The covered indications described above map to a range of diagnosis categories, but this policy does not identify them by code. Work with your coding team to assign ICD-10-CM codes that match the documented clinical indication — and code to the highest level of specificity your documentation supports. If you need guidance on which codes apply to your patient mix, consult your MAC or a qualified coding resource.

Do not use unspecified or generic codes — such as "encounter for lab testing" or "routine exam" — to support PT claims. The diagnosis on the claim must reflect the specific covered indication documented in the chart.