Use of the 50 Modifier vs. LT and RT Modifiers

Modifier 50 (bilateral) is used as a payment, rather than information, modifier. The addition of this modifier can affect payment depending on the procedure code and the BILAT SURG indicator. In some instances, procedure codes do not indicate on which side of the body a procedure is performed. In those instances, the modifier LT (left) or RT (right) is used to indicate the side of the body on which a service or procedure is performed. Specifically, modifiers LT and RT should be used to identify procedures that can be performed on contralateral anatomic sites (such as bones, joints), paired organs (such as ears, eyes, nasal passages, kidneys, lungs, ovaries), or extremities (such as arms or legs). Modifiers LT and RT should be used to indicate that the procedure is performed on only one side of the body.


Following are the indicators and their descriptions:


BILAT SURG indicator "0"

The 150% payment adjustment does not apply. When a procedure is reported with a modifier 50 or modifiers LT and RT base the payment for both sides on the lesser of the total charge or the fee schedule for a single code. For example, code XXXXX 50 is billed at $200. The allowed amount on a single code XXXXX is $125.00. Medicare will allow $125 for both services. Payment in full for both services is inappropriate because of physiology or anatomy, or the code description is for a unilateral code and a bilateral code exists. Most procedures on the skin are not bilateral procedures.

BILAT SURG indicator "1"

The 150% payment adjustment does apply. When the service is submitted with modifier 50, the LT and RT or with 2 units of service, then Medicare will allow the lower of the billed amount for both services or will allow 150% of the allowed amount for a single service. Medicare will allow the bilateral adjustment before the multiple procedure payment adjustment when the provider submits other services subject to the multiple surgery rules.

Note: The CMS Internet-Only Manual, Publication 100-04, Chapter 12, Section 40.7.B, indicates "If a procedure is not identified by its terminology as a bilateral procedure (or unilateral or bilateral), physician must report the procedure with modifier "-50". They report such procedure as a single line item."

BILAT SURG indicator "2"

The allowed amount is for a service performed bilaterally. Medicare could allow the lower of the actual charge or the fee schedule for a single service. The procedure code descriptor is bilateral, or unilateral or bilateral or the service is usually performed bilaterally. When billing for a procedure with a "2" indicator use one number of service and one line of service. Medicare will reject the services as unprocessable as these codes are inherently bilateral. i.e. CPT 32854, Lung Transplant, Double (Bilateral Sequential or en bloc); with cardiopulmonary bypass, is inherently bilateral.

BILAT SURG indicator "3"

The Medicare allowed amount is for 2 units of service. If the service is submitted using a modifier 50 or the RT/LT or two units of service, then Medicare will allow the fee schedule for both services. Apply the multiple surgery rules prior to applying the multiple payment reduction rules. Services in this category are generally radiology or other diagnostic tests and are not subject to the special payment rules for bilateral surgeries.

BILAT SURG indicator "9"

The bilateral payment adjustment concept does not apply.

Important Links (can be used to see payment policy indicators by CPT/HCPC): CMS Medicare Physician Fee Schedule (MPFS)


Appropriate Usage


  • Use modifier 50 when the code description does not already state the procedure is bilateral.
  • Use modifier 50 on bilateral body organs, such as the kidneys, ureters and hands.
  • When performing a procedure bilaterally during one session and the Medicare Physician Fee Schedule (MPFS) BILAT SURG indicator is 1 or 3.
  • Report codes with a BILAT SURG indicator of 1 on one line, appending modifier 50 and submit one unit of service.(Note: this differs from Current Procedural Terminology (CPT) instruction)
  • Report Codes with a BILAT SURG 3 on one line appending either modifier 50 or RT and LT using one unit of service or
  • Submit on one line using two units of service or
  • Submit on two lines of service using RT on one line and LT on the other with one unit of service each.


Inappropriate Usage


  • Reporting this modifier when performing the service on different areas of the same side of the body.
  • The BILAT SURG indicator is 0, 2, or 9.
  • When removing a lesion on the right arm and one on the left arm. Use the RT and LT modifiers.
  • Do not use modifier 50 for multiple procedures on one organ, such as the skin.
  • On a procedure code that is described as bilateral or unilateral or bilateral in its CPT description.
  • Do not report a bilateral procedure on two lines of service appending modifier 50 to the second line of service.


Additional Information


In general, the above information applies when two of the same procedure codes are performed on the same day for the same patient by the same provider or a member of the same group with the same specialty, there could be instances where two separate procedure codes are used. If so, Medicare's payment or denial would depend on any other type of rules and regulations concerning the individual services in question. This could include the National Correct Coding Initiative (NCCI) that could necessitate additional modifiers, duplicate edits, and global surgery edits.

Remember that each payer may establish its own guidelines and choose not to follow Medicare’s instructions. Also, each carrier may prefer representation of a bilateral procedure differently on a claim. For example, while most MACs prefer the use of modifier 50 on one claim line and as one unit, some carriers request appending modifiers LT and/or RT, either on 1 claim line or 2 lines. Some prefer the designation of 1 unit while others recommend 2 units. Check with your specific carriers to ensure compliance with each payers’ regulations.

Please contact Precision if you have any questions regarding the proper use of the 50, LT and RT modifiers.