Modifiers LT and RT: Telling the Payer Which Side of the Body Was Treated
Modifiers LT (left) and RT (right) identify which side of the body a procedure was performed on. They are informational — they do not change payment by themselves — but payers use them to enforce laterality edits, and missing or mismatched sides are a steady source of avoidable denials.
- Applies to
- Procedures on paired organs/structures (eyes, ears, limbs, kidneys, breasts) and DME
- Payment impact
- Informational — enables correct adjudication rather than changing rates
- Audit risk
- Low — the risk is denials and duplicate flags, not recoupments
- Common denial
- CO-4 for missing laterality; OA-18 duplicates on staged bilateral work
What do modifiers LT and RT do?
They state which side of the body received the procedure — left or right — on paired organs and structures: eyes, ears, lungs, kidneys, breasts, arms, legs, and their joints. Unlike payment modifiers, LT and RT do not reprice anything. Their job is context: they let the payer distinguish today's right-knee injection from last week's left-knee injection, enforce coverage rules that differ by side, and match professional claims to facility claims. Bilateral payment questions belong to modifier 50.
When do you use them?
On every unilateral procedure performed on a paired structure, and whenever the payer's edits require laterality. Realistic example: an ophthalmologist performs cataract surgery on the right eye — 66984-RT. Three weeks later the left eye is done inside the first global period: 66984-79-LT. The LT is what makes the second claim visibly a different eye; without it, the payer's systems see a same-code repeat and the 79 claim fights a duplicate edit it should never have faced.
- Unilateral surgery, injections, and imaging on paired structures.
- DMEPOS items made for one side (orthoses, prostheses).
- Staged bilateral procedures across separate dates.
- Payers requiring two-line LT/RT billing instead of modifier 50.
When are they wrong or a denial trigger?
- LT/RT plus modifier 50 on one line. Redundant and contradictory — pick the payer's single convention.
- Midline or unpaired structures. Laterality on a code for a midline organ invites a CO-4.
- Side mismatches. Claim says RT, note says left — an instant denial if caught pre-pay, and a documentation finding if caught post-pay. This is the most common laterality error and it is almost always a charge-entry default, not a coding decision.
- Substituting LT/RT for XS. Laterality alone does not defeat NCCI edits; anatomically distinct bundled services need XS analysis.
What are the documentation and payment impacts?
Payment impact is indirect but real: correct laterality prevents duplicate denials on staged procedures, keeps OA-18 off your remits, and preserves global-period tracking per side. Documentation must state the side in the procedure note header and body, matching the consent and the claim. For practices doing volume on paired structures — ophthalmology, orthopedics, interventional pain — laterality hygiene is one of the cheapest denial-prevention investments available.
Frequently asked questions
No. They are informational HCPCS modifiers. Payment changes come from modifier 50 (bilateral, 150% under Medicare) or payer-specific two-line LT/RT bilateral conventions. What LT/RT do is let the claim adjudicate correctly — and stop false duplicate denials on paired-organ procedures.
When the payer says so. Medicare wants indicator-1 bilateral procedures on one line with modifier 50, but many commercial payers and some Medicaid programs require two lines, one LT and one RT. Keep the convention in your payer grid; both approaches paid correctly yield the same 150% total.
Certain codes — many ophthalmic, orthopedic, and DME codes — carry payer edits requiring a laterality modifier. Submitting them bare triggers CO-4 (modifier inconsistent or required modifier missing). The fix is a corrected claim with LT or RT matching the documentation.
Indirectly, yes. ICD-10 laterality (left/right/bilateral characters) must agree with the LT/RT on the procedure line. A right-eye diagnosis with an LT procedure modifier is an easy front-end rejection and, worse, a medical-record integrity problem in audits.
Sources & further reading
Reviewed by the ImmediCare Solutions RCM team
Certified billers and coders handling claims across 50+ specialties nationwide. This entry is reviewed against current payer policy and CMS rules. Last review: Jul 5, 2026.
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