When a physician performs the exact same procedure on both the left and right sides of the body during the same session, you must use Modifier 50 (Bilateral Procedure).
The 150% Payment Rule
For most procedures (including major joint injections like 20610 or epidurals like 64483), Medicare does not pay 200% for doing both sides. Instead, they apply a multiple procedure reduction.
Medicare will pay 100% of the fee schedule for the first side, and 50% of the fee schedule for the second side (totaling 150%).
How to Format the Claim Line
Medicare requires you to bill bilateral procedures on a single line item with 1 unit and Modifier 50 appended (e.g., 20610-50 x 1 unit). Do not bill it on two separate lines with RT and LT, as Medicare will deny the second line as a duplicate.
Note: Some commercial payers DO require two lines with RT/LT. Always verify with your clearinghouse.
NCCI Edits and Inherent Bilateral Codes
Never append Modifier 50 to a code whose descriptor already states "bilateral" (e.g., 64615 for Botox, or 93880 for carotid ultrasound). The payer will instantly deny it.