Laboratory tests not medically necessary (Updated for 2026)

Common Causes for L1

Denials with code L1 typically happen for the following specific reasons:

• The ICD-10-CM diagnosis code submitted on the claim is not listed as an approved or covered indication under the payer's active LCD or NCD policy for the billed laboratory test.
• Routine screening laboratory tests were billed with diagnostic codes, or vice versa, without matching the specific medical necessity criteria or preventive service guidelines.
• The laboratory test exceeded the allowable frequency limits established by CMS or commercial payers for the patient's specific diagnosis or condition within a given timeframe.
• Failure to document clinical signs, symptoms, or a relevant history in the medical record that justifies ordering a specialized or non-routine laboratory panel.

How to Prevent L1 Denials

To avoid receiving this denial in the future, implement these specific checks:

• Implement automated medical necessity scrubbing software within the EHR and billing system to cross-reference ordered laboratory CPT codes against active LCD/NCD diagnosis lists prior to testing.
• Secure a signed Advance Beneficiary Notice of Noncoverage (ABN) for Medicare beneficiaries, or a commercial waiver, whenever a laboratory test is expected to fall outside of medical necessity criteria.
• Train ordering clinicians to document specific signs, symptoms, or established diagnoses in the lab order rather than relying on generic or screening codes.
• Establish routine clinical audits of laboratory orders to verify that frequency limits are monitored and that repeat tests are supported by documented clinical progression or therapy changes.

Appeal Letter Template for L1

If you believe this claim was denied incorrectly, you can use the following template to submit an appeal.

[Your Practice Header]
[Date]

[Payer Name]
[Appeals Department Address]

RE: Appeal for Claim [Claim Number]
Patient: [Patient Name]
ID: [Patient ID]
Date of Service: [Date]
Denial Code: L1 - Laboratory tests not medically necessary

Dear Appeals Department,

I am writing to appeal the denial of the above-referenced claim, which was denied with code L1: "Laboratory tests not medically necessary".

We are appealing the denial of the laboratory service(s) billed under CPT code(s) for the date of service, which was denied under code L1 for lack of medical necessity. Upon comprehensive clinical review of the patient's medical record, the ordered laboratory test was highly indicated and necessary for the diagnostic workup and ongoing management of the patient's documented condition, specifically. Per CMS National Coverage Determinations (NCD) and Local Coverage Determinations (LCD) guidelines, the attached clinical documentation clearly demonstrates that the patient exhibited signs, symptoms, and a clinical history that justified this test, meeting all requirements under Section 1862(a)(1)(A) of the Social Security Act. We respectfully request that you review the enclosed clinical records, reverse this denial, and process the claim for full reimbursement.

Attached please find:
1. A copy of the original claim.
2. The relevant medical records supporting the service.
3. [Any other supporting documents].

We respectfully request that you reprocess this claim for payment.

Sincerely,

[Your Name]
[Title]
[Practice Name]