Medicare Bilateral Surgery Rules: A Small Modifier That Can Make a Big Difference

In medical coding and compliance, the little things matter. Bilateral surgery billing is a good example of that. One small modifier can change how a claim is paid.

A bilateral surgery is a procedure performed on both sides of the body during the same operative session or on the same day. Think of procedures performed on both knees, both eyes, both ears, or both wrists.

At first glance, billing these services may seem straightforward. But Medicare has specific rules about when modifier -50 should be used.

If the CPT code does not already include the words “bilateral” or “unilateral or bilateral,” Medicare generally wants the procedure reported on one line with modifier -50.

This is where coders can get tripped up. CPT coding guidelines may instruct providers to report the procedure on two separate lines using RT and LT. Medicare, however, usually wants one line with modifier -50.

There are also times when modifier -50 should not be used. Some CPT codes already include bilateral work in the code description. For example, CPT 27395 includes the word “bilateral,” and CPT 52290 includes “unilateral or bilateral.” In these cases, the fee schedule already accounts for the extra work.

Medicare uses the bilateral surgery indicator in the Medicare Physician Fee Schedule Database to determine how the service should be paid. When the bilateral indicator is 1, Medicare generally pays 150 percent of the fee schedule amount.

From my experience, this is one of those details that can easily be overlooked until a claim is underpaid or denied. A procedure may have been coded correctly in every other way, but if modifier -50 is used incorrectly, the payment may not come out as expected.

That is why I always recommend checking both the CPT description and the Medicare bilateral indicator before the claim is submitted.

Bilateral surgery billing may seem like a small detail, but it can have a big impact on reimbursement. Taking a few extra minutes to verify the rules can save a lot of time and frustration later.

Sometimes one small modifier can change the entire payment.

Reference:

Centers for Medicare & Medicaid Services. (2025). Medicare Claims Processing Manual, Chapter 12, § 40.7, Claims for Bilateral Surgeries. U.S. Department of Health and Human Services.