ModifiedPremera BluecrossPolicy N/A

Modifier 23 - Unusual Anesthesia

Defines when the Plan recognizes and reimburses services appended with anesthesia Modifier 23 on professional claims across Premera Blue Cross and affiliated lines of business. Applies to anesthesia CPT codes 00100-01999 and explains modifier sequencing, exclusions, documentation expectations, and contractual exceptions.

Policy Summary

PayerPremera Bluecross

PolicyModifier 23 - Unusual Anesthesia

Policy CodePolicy N/A

Change TypeArchived; prior clarifications and corrections

Effective Date

Next Review Date

Key ActionProviders must sufficiently document in the member's medical record the unusual circumstances that required general or monitored anesthesia for a procedure that normally does not require it.

SourceLink

POLICY UPDATE CHANGES

Policy archived effective April 2, 2026.

Clarification that Modifier 23 is not appropriate with moderate/conscious sedation codes (99151-99153, 99155-99157).

Clarified that the performing surgeon would NOT append modifier 23 to the main surgical procedure but continue to append modifier 47 only when they perform general or monitored anesthesia along with the surgical procedure.

Clarified policy applies to claims submitted on CMS 1500 or 837P claim forms.

00100-01999Primary CPT code range governed

99151-99153, 99155-99157Excluded CPT code blocks (sedation)

AA, AD, QK, QS, QX, QY, QZKey anesthesia modifiers referenced

Policy summary

This policy defines when Premera Blue Cross and affiliated lines of business recognize and reimburse professional claims appended with Modifier 23 (Unusual Anesthesia). It provides guidance on appropriate use, sequencing with primary anesthesia modifiers (AA, AD, QK, QS, QX, QY, QZ), and notes that coverage is subject to member eligibility, benefit limits, and the Plan's medical and coding policies.

Modifier 23 is recognized when appended to an anesthesia procedure that normally does not require anesthesia or local anesthesia but must be performed under general or monitored anesthesia due to unusual circumstances that are sufficiently documented; it is limited to anesthesia CPT codes 00100-01999 and must be added after the primary anesthesia modifier. The policy also clarifies that Modifier 23 is not appropriate for moderate/conscious sedation codes (99151-99153, 99155-99157) and explains the alternative reporting when a surgeon provides anesthesia (append Modifier 47 to the surgical procedure and do not bill a separate anesthesia code).

Status: MODIFIED. Note: This policy has a version history including clarifications (05/27/21, 05/19/23) and is archived effective April 2, 2026.

Policy Header Metadata

Policy TitleModifier 23 - Unusual Anesthesia

PayerPremera Blue Cross

Policy NumberN/A

StatusMODIFIED

Last review2026-03-12

Effective date

Scope summaryDefines when the Plan recognizes and reimburses services appended with anesthesia Modifier 23 on professional claims across Premera Blue Cross and affiliated lines of business. Applies to anesthesia CPT codes 00100-01999 and explains modifier sequencing, exclusions, documentation expectations, and contractual exceptions.

Recognition and exclusions for Modifier 23

Recognition of Modifier 23

Modifier 23 is recognized when ALL of the following are met:

ALL of the following

Modifier 23 is appended to an anesthesia procedure that normally does not require anesthesia or local anesthesia and must be performed under general or monitored anesthesia as a result of unusual circumstances.
Unusual circumstances are sufficiently documented in the member's medical records.
Modifier 23 is used only with general or monitored anesthesia procedure codes CPT 00100-01999.
Modifier 23 is added after the primary anesthesia modifier which identifies whether the service was personally performed, medically directed, or medically supervised (Modifiers AA, AD, QK, QS, QX, QY, QZ).

Applicable CPT codes and modifiers

Allowed anesthesia CPT codes for Modifier 23CPTCovered

00100-01999

General or monitored anesthesia procedure codes; modifier 23 only used with these codes

Primary anesthesia modifiers (must precede Modifier 23)Modifier

AA	Anesthesia services performed personally by anesthesiologist
AD	Medical supervision by anesthesiologist; more than four concurrent anesthesia procedures
QK	Medical direction of two, three, or four concurrent anesthesia procedures involving qualified individuals
QS	Monitored anesthesia care service
QX	CRNA service: with medical direction by a physician
QY	Medical direction of one CRNA by an anesthesiologist
QZ	CRNA service: without medical direction by a physician

Excluded CPT codes (modifier 23 not appropriate)CPTNot Covered

99151-99153	Moderate/conscious sedation codes — Modifier 23 not appropriate
99155-99157	Moderate/conscious sedation codes — Modifier 23 not appropriate

Surgical anesthesia reporting alternativeModifier

47	Anesthesia by Surgeon — surgeon should append modifier 47 to main surgical procedure when surgeon provides anesthesia; should not bill separate anesthesia code

Billing rules, documentation, and denial risk

Billing Rule

Modifier sequencing

Append Modifier 23 after the primary anesthesia modifier when billing applicable anesthesia CPT codes.

00100-01999
AA
AD
QK
QS
QX
QY
QZ
23

Billing Rule

Do not append to moderate/conscious sedation

Key terms

Definitions

Modifier 23Used when an anesthesia procedure that normally does not require anesthesia or local anesthesia must be performed under general or monitored anesthesia due to unusual circumstances.

Policy changes and archive history

06/15/20Clarified in the Purpose statement that the policy applies to claims submitted on a CMS 1500 or 837P claim form.

Clarified policy applies to claims submitted on CMS 1500 or 837P claim forms.

05/27/21Added in 05/27/21 version.

Clarification that Modifier 23 is not appropriate with moderate/conscious sedation codes (99151-99153, 99155-99157).

05/19/23Correction noted 05/19/23.

Policy Summary

PayerPremera Bluecross

PolicyModifier 23 - Unusual Anesthesia

Policy CodePolicy N/A

Change TypeArchived; prior clarifications and corrections

Effective Date

Next Review Date

SourceLink

On This Page

Not Appropriate Uses / Exclusions

The following uses are NOT appropriate:

ANY of the following

Modifier 23 is not appropriate to be appended to moderate/conscious sedation codes (99151-99153, 99155-99157).
If a surgeon provides the general or monitored anesthesia during the surgical procedure they are performing, the surgeon reports services by adding modifier 47 (Anesthesia by Surgeon) to the main surgical procedure only and does not also bill a separate anesthesia code (00100-01999).

Do not append Modifier 23 to moderate/conscious sedation codes; use appropriate sedation coding instead.

99151-99153
99155-99157

Billing Rule

Surgeon-provided anesthesia reporting

When a surgeon provides general or monitored anesthesia during the surgical procedure they are performing, report modifier 47 on the main surgical procedure and do not bill a separate anesthesia code.

00100-01999
47

Documentation Required

Document unusual circumstances

Providers must sufficiently document the unusual circumstances in the member's medical record that required general or monitored anesthesia for a procedure that normally does not require it.

Denial Risk

Claim denial or adjustment risk

Claims may be denied, audited, or adjusted if Modifier 23 is used without adequate documentation or applied to disallowed codes; violations may trigger increased auditing, contractual penalties, or other disciplinary actions.

04/02/26Policy archived effective April 2, 2026.Latest

Policy archived effective April 2, 2026.