Modifier 23- Unusual Anesthesia

Identifies anesthesia services provided under circumstances that make anesthesia unusually difficult or necessary for a procedure that typically does not require it.

What Is Modifier 23?

Modifier 23 is used to identify unusual anesthesia circumstances that go beyond what would ordinarily be expected for the procedure being performed.

It may apply when a procedure that normally does not require general anesthesia must be performed under anesthesia because of the patient's condition, age, behavior, anatomy, or another significant clinical circumstance.

The modifier communicates that anesthesia was necessary because the case presented circumstances that were unusual compared with the typical performance of the procedure.

Modifier 23 should not be added simply because anesthesia was difficult or because an anesthesia professional participated in the case. The medical record should clearly establish the unusual circumstances supporting its use.

When to Use Modifier 23

Procedure Normally Requires No Anesthesia: Anesthesia becomes necessary for a procedure that would ordinarily be performed without it.

Patient Cannot Cooperate: A patient's age, cognitive status, developmental condition, or other clinical circumstance prevents the procedure from being safely completed without anesthesia.

Unusual Patient Condition: A significant medical or physical condition makes anesthesia necessary under circumstances where it would not normally be required.

Unexpected Clinical Circumstance: An unusual condition substantially changes the anesthesia requirements of the procedure.

Documentation Supports Unusual Circumstances: The anesthesia and medical records clearly explain why the circumstances were outside the ordinary requirements of the procedure.

When NOT to Use Modifier 23

Anesthesia Is Routinely Required: Do not use Modifier 23 when anesthesia is normally expected for the procedure.

Routine Anesthesia Difficulty: A case should not receive Modifier 23 merely because the anesthesia service required additional attention or effort.

No Documented Unusual Circumstance: The modifier should not be reported when the record does not explain why the anesthesia was unusual.

Monitored Anesthesia Care: Modifier QS identifies monitored anesthesia care and should not be replaced by Modifier 23 solely because MAC was provided.

Payment Adjustment Only: Do not append Modifier 23 merely in an attempt to increase reimbursement without qualifying clinical circumstances.

Billing Example

A young patient requires a diagnostic procedure that is ordinarily performed without general anesthesia.

Because the patient cannot remain still or cooperate sufficiently for the procedure to be completed safely, the physician determines that general anesthesia is medically necessary.

The anesthesia professional documents the patient's condition, the reason anesthesia was necessary, and the anesthesia service provided.

The appropriate anesthesia code is reported with Modifier 23 to identify the unusual anesthesia circumstances.

Documentation Requirements

Unusual Circumstance: Clearly document the specific condition or circumstance that made the anesthesia unusual.

Reason for Anesthesia: Explain why the procedure could not reasonably or safely be performed using the usual approach.

Patient Condition: Document relevant medical, developmental, behavioral, anatomical, or other clinical factors.

Anesthesia Service: Maintain a complete anesthesia record describing the service provided.

Anesthesia Time: Record accurate anesthesia start and stop times when applicable.

Medical Necessity: Documentation should establish why the additional or unusual anesthesia service was medically necessary.

Billing and Claim Considerations

Modifier 23 should be supported by circumstances that distinguish the anesthesia service from what is ordinarily required for the procedure.

The modifier does not change the underlying anesthesia code. Instead, it provides additional information indicating that unusual circumstances affected the anesthesia service.

CMS's current anesthesia resources direct providers to Medicare's anesthesia claims rules, while the 2026 NCCI Policy Manual continues to establish the broader Medicare coding rules applicable to anesthesia services.

Providers should not assume that reporting Modifier 23 automatically results in additional payment. Coverage and reimbursement can depend on the payer, procedure, clinical circumstances, and supporting documentation.

The medical record should make the unusual nature of the anesthesia readily apparent if the claim is reviewed.

Common Billing Mistakes

Using Modifier 23 for Routine Anesthesia: The modifier should not be appended when anesthesia is normally expected for the procedure.

Insufficient Documentation: The record does not explain what made the anesthesia circumstances unusual.

Using Modifier 23 for Additional Time Alone: A longer anesthesia service does not automatically establish unusual anesthesia.

Confusing Modifier 23 With QS: QS identifies monitored anesthesia care, while Modifier 23 identifies unusual anesthesia circumstances.

Automatic Modifier Use: Modifier 23 should be determined from the individual clinical circumstances rather than routinely appended to selected procedures.

Assuming Additional Payment: The modifier does not guarantee increased reimbursement.

Common Denial Reasons

Unusual Circumstance Not Supported: Documentation does not establish why the anesthesia was unusual.

Anesthesia Is Routine for the Procedure: The payer determines that the anesthesia reported is ordinarily expected.

Medical Necessity Is Unclear: Records do not explain why the anesthesia approach was medically necessary.

Documentation Is Incomplete: The anesthesia record lacks sufficient clinical information.

Incorrect Modifier: Another anesthesia modifier better represents the service provided.

Payer Requirements Not Met: The claim does not satisfy the payer's requirements for reporting unusual anesthesia.

Modifier 23 vs. Modifier QS

Modifier 23: Identifies unusual anesthesia circumstances.

Modifier QS: Identifies monitored anesthesia care and is an informational anesthesia modifier.

Modifier 23 describes why the anesthesia circumstances were unusual, while QS identifies the type of anesthesia care provided. CMS currently identifies QS as an informational MAC modifier that is reported with actual anesthesia time and an appropriate anesthesia payment modifier.

Modifier 23 vs. Modifier 47

Modifier 23: Identifies unusual circumstances surrounding an anesthesia service.

Modifier 47: Identifies regional or general anesthesia provided by the surgeon performing the procedure.

The modifiers address different circumstances: Modifier 23 concerns the unusual nature of the anesthesia, while Modifier 47 identifies who administered the anesthesia.

Frequently Asked Questions

Does Modifier 23 mean the anesthesia procedure took longer than expected?
Not necessarily. Additional time alone does not define unusual anesthesia. Documentation should establish the clinical circumstances that made the anesthesia unusually necessary or difficult.

Does Modifier 23 automatically increase anesthesia reimbursement?
No. Reporting Modifier 23 communicates unusual anesthesia circumstances, but payment depends on the payer's policies, the service reported, and the supporting documentation.