If you look up specific code in Medicare fee schedule online, by modifier you can click on "detail" that will show you the specific bilateral modifier indicator (0,1,2,3,9), here are the explanations of indicators:
Indicator Number Description
0 The 150 percent adjustment for bilateral procedures does not apply. Do not submit codes with bilateral indicator '0' with HCPCS modifier RT or LT or CPT modifier 50. Submission of these modifiers may result in a denial. Payment will be based on the lower of the actual charge for both sides or 100 percent of the fee schedule amount for a single code. The bilateral adjustment is not appropriate for codes with Indicator '0' because of (a) physiology or anatomy, or (b) because the code descriptor specifically states that it is a unilateral procedure and there is an existing code for a bilateral procedure.
1 The 150 percent adjustment for bilateral procedures applies. Bilateral procedures must be reported with CPT modifier 50 and a quantity of '1'. When the code is reported with CPT modifier 50, payment will be based on the lower of the total actual charge for both sides or 150 percent of the fee schedule amount for a single code. Note that the bilateral pricing rules are applied before other 'multiple procedure' rules. Submission of modifiers other than 50 may result in a denial.
2 The 150 percent adjustment for bilateral procedures does not apply. Do not submit codes with bilateral indicator 2 with HCPCS modifier RT or LT or CPT modifier 50. The Relative Value Units (RVUs) are already based on the procedure being performed as a bilateral procedure. If the code is reported with CPT modifier 50 or is reported twice on a single date, payment will be based on the lower of the total actual charges by the physician for both sides or 100 percent of the fee schedule amount for a single code. If codes with bilateral indicator 2 are submitted with HCPCS modifier RT or LT or CPT modifier 50, the claim will be rejected as a 'billing error.' These claims must be corrected and resubmitted as new claims.
3 The 150 percent adjustment for bilateral procedures does not apply. Payment will be based on the lower of 100 percent of the fee schedule for each side or actual charges for each side. Report bilateral procedures with CPT modifier 50 and a quantity of '2' or report on separate detail lines with HCPCS modifiers RT and LT. Services in this category are generally radiology procedures or other diagnostic tests which are not subject to the special payment rules for other bilateral procedures.
9 Concept does not apply. This indicator often appears in the CO SURG column for nonsurgical procedures.
Reference:
Complete definitions of bilateral indicators are available in CMS Pub. 100-04, Chapter 23 (PDF, 1.47 MB), in the Addendum following Section 90