Modifier 50: Bilateral Procedures and the 150% Rule
Modifier 50 reports the same procedure on both sides of the body. Which codes take it, how Medicare pays 150% on one line, and when RT and LT fit instead.
Modifier 50 is a billing modifier that reports the same procedure performed on both sides of the body in the same session. For codes Medicare marks as eligible (bilateral indicator 1), it pays 150% of the one-side fee schedule amount, billed on a single line with one unit.
Key takeaways
- Check the code's bilateral indicator first. Only indicator 1 gets the 150% adjustment.
- Medicare wants one line, the code with 50, and one unit. That differs from the two-line convention used by some other payers.
- Codes already described as bilateral, or "unilateral or bilateral," never take 50.
- Midline structures and different procedures on each side don't qualify.
- The bilateral total is ranked as one procedure before the multiple procedure reduction.
Modifier 50 · payment effect
With and without the modifier
20610 without 50 · national office
$68.81
Joint injection
20610-50 · Bilateral: 150%
$103.22
Both sides on one line with modifier 50 are paid at 150% of the fee schedule amount (subject to multiple-procedure rules with other procedures).
What modifier 50 means
Some procedures are routinely done on one side, but occasionally on both: a joint injection, a carpal tunnel release, an inguinal hernia repair, a knee replacement. When both sides are done in the same session, modifier 50 tells the payer the code was performed bilaterally. The second side doesn't cost as much as the first (the patient is already prepped and the session already open), so Medicare pays 150%, not 200%.
The bilateral indicator in the Physician Fee Schedule relative value file decides how each code is treated:
| Indicator | Medicare rule if billed bilaterally |
|---|---|
| 0 | No 150% adjustment; both sides paid at 100% of one side total. Usually anatomy or an existing bilateral code. |
| 1 | 150% of the one-side amount |
| 2 | Already priced as bilateral; 100% total, don't use 50 |
| 3 | Each side paid at 100% (mostly radiology and diagnostic tests) |
| 9 | Bilateral concept doesn't apply |
CMS payment indicators · 20610
Joint injection
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 000 | Same-day global: pre- and post-op care on the day of the procedure is included. |
| Multiple procedures | 2 | Standard reduction: highest-valued procedure at 100%, others at 50%. |
| Bilateral (modifier 50) | 1 | Bilateral with modifier 50 pays 150% of the fee schedule amount. |
| Assistant at surgery (80/81/82/AS) | 1 | Not paid (statutory restriction). |
| Co-surgeons (62) | 0 | Not permitted. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 0 | Physician service: no professional/technical split. |
When to use modifier 50
- The same code on both sides in one session, when the code's bilateral indicator is 1. Arthrocentesis or injection of both knees (20610), bilateral carpal tunnel release (64721), bilateral inguinal hernia repair (49505), bilateral total knee replacement (27447).
- Medicare format: one line, code plus 50, one unit, charge for both sides. Medicare also recognizes the same code twice with RT and LT, or two units, and prices it the same way.
- Other payers: some want two lines (one plain, one with 50) or RT and LT. CMS specifies a one-line format for Medicare. Follow each payer's format.
When not to use modifier 50
Also skip 50:
- Midline organs with no right and left, such as the bladder, uterus or nasal septum.
- Different procedures on each side, or the same procedure on different body areas (right shoulder and left knee). Use RT and LT, and 59 or XS only if an NCCI edit applies.
- Codes with indicator 0 or 9. The adjustment doesn't apply.
- Radiology with indicator 3. Each side is paid separately at 100%; follow the payer's RT/LT instructions.
- A bilateral code done on one side only. That's modifier 52.
How modifier 50 affects payment
For bilateral indicator 1, Medicare pays the lower of the total charge for both sides or 150% of the fee schedule amount for a single code (Pub. 100-04, ch. 12, §40.7). If other procedures are billed that day, the bilateral amount is calculated first and then ranked with the rest under the multiple procedure rule (100% for the highest, 50% for the others).
Global surgery rules apply as usual: one global period covers both sides.
Modifier 50 vs RT/LT, 51 and 59
| Modifier | Use it when | Payment effect |
|---|---|---|
| 50 | Same code, both sides, same session | 150% (indicator 1) |
| RT / LT | Identify the side; some payers want them instead of 50 | Same pricing as 50 when both sides are billed |
| 51 | Additional different procedures in the session | 50% for each additional procedure |
| 59 | Two bundled services were separate | None; lets the bundled code pay |
FAQ
What is the 50 modifier used for?
To report the same procedure done on both sides of the body in one session, so the payer pays the bilateral amount instead of denying the second side as a duplicate.
What is the difference between modifier 50 and 59?
50 is for the same procedure on both sides. 59 says two different services that usually bundle were separate. CMS's guidance on 59 says to use anatomic modifiers such as RT and LT, not 59, when procedures are on different sides.
Does modifier 50 increase payment?
Yes, for codes with bilateral indicator 1: Medicare pays 150% of the one-side amount. For other indicators, it doesn't add payment.
When not to use modifier 50?
On codes that are already bilateral by definition, on midline organs, when different procedures were done on each side, and on codes whose bilateral indicator isn't 1.
How many units do you bill with modifier 50?
One, for Medicare. The 150% adjustment comes from the modifier, not the unit count.
Keep reading
- Modifier 51 for multiple procedures in a session.
- Modifier 52 for a bilateral code done on one side.
- Modifier 59 for bundled pairs on different sites.
- Codes on this page: 20610 64721 49505 27447
Sources: Medicare Claims Processing Manual, Pub. 100-04, ch. 12, §40.6.C.16 and §40.7 (Claims for Bilateral Surgeries); CMS National Physician Fee Schedule Relative Value File, CY 2026 (RVU26D), bilateral surgery indicator; Noridian JE Part B, Modifier 50; CMS MLN1783722 (April 2026). Verified October 6, 2026.
