Short answerFor procedures eligible for bilateral payment, Medicare pays 150% of the fee schedule amount for a single line billed with modifier 50. Commercial payers follow their own contracts and billing formats. Lines allowed at 100% when the contract allows more are underpayments.
Bilateral injections are routine in pain management: transforaminal epidurals, facet injections, SI joints. They are also a common underpayment, because a bilateral line paid as one side looks like a normal payment.
How bilateral billing works
- Medicare uses a bilateral surgery indicator for each code in the Physician Fee Schedule. For indicator 1 codes, the procedure is billed on one line with modifier 50 and one unit, and paid at 150% of the fee schedule amount.
- Commercial payers may require modifier 50 on one line, RT and LT on two lines, or two units. Check each payer's policy and your contract.
Where it goes wrong
| Problem | Effect |
|---|---|
| Payer allows 100% on a modifier 50 line | Half the second side unpaid |
| Wrong format for the payer (50 vs RT/LT) | Denial or one side paid |
| Code not eligible for bilateral payment | Modifier 50 rejected; each side handled per the indicator |
| Add-on codes billed bilaterally incorrectly | Denial of the add-on |
How to check your remittances
- List bilateral claims for the last 90 days.
- Compare the allowed amount with the contract's bilateral rule.
- Group shortfalls by payer and code.
Fixing it
Bill in each payer's required format, and send reconsiderations for short-paid lines with the contract language attached. Repeated short payments on the same code are worth raising with provider relations.
Related: what is an underpayment and pain management billing.
This article is general billing information, not legal or coding-compliance advice. Payer rules, CPT descriptors and federal guidance change; check the current versions for your claims.