A modifier provides the means by which the reporting physician or provider can indicate that a service or procedure that has been performed has been altered by some specific circumstance but not changed in its definition or code.
Level I modifiers are codes and descriptors copyrighted by the American Medical Association's current procedural terminology (CPT).
Level II modifiers are codes and descriptors approved and maintained jointly by the alpha-numeric editorial panel (consisting of CMS, the Health Insurance Association of America, and the Blue Cross and Blue Shield Association).
| Modifier | Description | Effective | |
|---|---|---|---|
| G6 | Esrd patient for whom less than six dialysis sessions have been provided in a month | May 01, 1998 | |
| G7 | Pregnancy resulted from rape or incest or pregnancy certified by physician as life threatening | Jul 01, 1999 | |
| G8 | Monitored anesthesia care (mac) for deep complex, complicated, or markedly invasive surgical procedure | Jul 01, 1999 | |
| G9 | Monitored anesthesia care for patient who has history of severe cardio-pulmonary condition | Jul 01, 1999 | |
| GA | Waiver of liability statement issued as required by payer policy, individual case | Jan 01, 2011 | |
| GB | Claim being re-submitted for payment because it is no longer covered under a global payment demonstration | Jan 01, 2002 | |
| GC | This service has been performed in part by a resident under the direction of a teaching physician | Jan 01, 2001 | |
| GD | Units of service exceeds medically unlikely edit value and represents reasonable and necessary services | Jan 01, 2020 | |
| GE | This service has been performed by a resident without the presence of a teaching physician under the primary care exception | Jan 01, 1997 | |
| GF | Non-physician (e.g. nurse practitioner (np), certified registered nurse anesthetist (crna), certified registered nurse (crn), clinical nurse specialist (cns), physician assistant (pa)) services in a critical access hospital | Apr 01, 2003 | |
| GG | Performance and payment of a screening mammogram and diagnostic mammogram on the same patient, same day | Jan 01, 2002 | |
| GH | Diagnostic mammogram converted from screening mammogram on same day | Oct 01, 1998 | |
| GJ | "opt out" physician or practitioner emergency or urgent service | Oct 01, 1998 | |
| GK | Reasonable and necessary item/service associated with a ga or gz modifier | Jan 01, 2008 | |
| GL | Medically unnecessary upgrade provided instead of non-upgraded item, no charge, no advance beneficiary notice (abn) | Jan 01, 2008 | |
| GM | Multiple patients on one ambulance trip | Jan 01, 2002 | |
| GN | Services delivered under an outpatient speech language pathology plan of care | Jan 01, 2003 | |
| GO | Services delivered under an outpatient occupational therapy plan of care | Jan 01, 2003 | |
| GP | Services delivered under an outpatient physical therapy plan of care | Jan 01, 2003 | |
| GQ | Via asynchronous telecommunications system | Oct 01, 2001 | |
| GR | This service was performed in whole or in part by a resident in a department of veterans affairs medical center or clinic, supervised in accordance with va policy | Jan 01, 2006 | |
| GS | Dosage of erythropoietin stimulating agent has been reduced and maintained in response to hematocrit or hemoglobin level | Jan 01, 2013 | |
| GT | Via interactive audio and video telecommunication systems | Jan 01, 1999 | |
| GU | Waiver of liability statement issued as required by payer policy, routine notice | Jan 01, 2011 | |
| GV | Attending physician not employed or paid under arrangement by the patient's hospice provider | Jan 01, 2002 |