Double-Charge Detector 0518U

Ther rx mntr 90+ pn&mtl hlth — 66 bundling rules

If your bill lists 0518U alongside any of these codes as separate charges, it may be an unbundling error.

By Priya Iyengar , Senior Billing Analyst · Published March 15, 2026 · Updated April 3, 2026

About the analyst

Priya Iyengar leads the billing code review team at BillRazor Research. She analyzes NCCI bundling edits, DRG coding, and regional rate variation. Expertise: NCCI bundling, DRG analysis, regional pricing.

NCCI edit data

66 code pairs

Updated 2026-04-03

Bundling rules — 0518U

NCCI edits: these codes have billing restrictions when billed with 0518U

Research suggests 49–80% of hospital bills contain errors. Our system checks every line item against Medicare benchmarks.

Common unbundling errors — medical procedures

Unbundling occurs when medical providers bill two separate codes for services that should be combined into a single charge according to National Correct Coding Initiative (NCCI) rules. In other procedures including anesthesia, radiology, pathology, and miscellaneous support services, common unbundling patterns include separately billing diagnostic imaging with its professional interpretation when both should be included in one comprehensive code, and charging for basic monitoring or preparation services alongside the primary procedure when these components are considered integral parts of the main service. Another frequent error involves billing multiple pathology examination codes for what constitutes a single comprehensive analysis. With 809 other codes subject to bundling restrictions in the NCCI database, these errors create charges above the benchmark for patients who receive multiple bills for what should constitute one complete service. The potential difference between unbundled billing and correct coding practices can significantly impact patient financial responsibility, as they may face duplicate charges for components of care that medical coding standards define as a single billable service.

What to check on your bill

When reviewing itemized bills for procedure bundling issues, patients should examine several key areas to identify potential billing irregularities. Look for multiple procedure codes billed on the same date that represent components of a comprehensive service, such as separate charges for incision, repair, and closure when these steps are typically included in one primary procedure code. Watch for code patterns where related procedures share the same first three digits, as these often indicate services that should be bundled together under Medicare's Correct Coding Initiative. Check for appropriate modifier usage, particularly modifier 59 or XS, which legitimately allow separate billing when procedures are performed on different anatomical sites or during distinct sessions. Without proper modifiers, separately billed related procedures may represent charges above the benchmark. Compare your itemized statement against standard bundling practices for your specific procedure type to identify potential differences in billing patterns.

All bundling rules for 0518U

66 code pairs that have billing restrictions with this procedure.

Never bill together

May bill with modifier

Code	Description	Rule
0119U	Crd ceramides liq chrom plsm	May bill with modifier
0517U	Ther rx mntr 80+ psyactiv rx	May bill with modifier
80150	Assay of amikacin	May bill with modifier
80155	Drug assay caffeine	May bill with modifier
80156	Assay carbamazepine total	Never bill together
80157	Assay carbamazepine free	Never bill together
80158	Drug assay cyclosporine	May bill with modifier
80159	Drug assay clozapine	May bill with modifier
80162	Assay of digoxin total	May bill with modifier
80163	Assay of digoxin free	May bill with modifier
80164	Assay dipropylacetic acd tot	Never bill together
80165	Dipropylacetic acid free	Never bill together
80168	Assay of ethosuximide	Never bill together
80169	Drug assay everolimus	May bill with modifier
80170	Assay of gentamicin	May bill with modifier
80171	Drug screen quant gabapentin	Never bill together
80173	Assay of haloperidol	Never bill together
80175	Drug screen quan lamotrigine	Never bill together
80176	Assay of lidocaine	May bill with modifier
80177	Drug scrn quan levetiracetam	May bill with modifier
80178	Assay of lithium	Never bill together
80180	Drug scrn quan mycophenolate	May bill with modifier
80183	Drug scrn quant oxcarbazepin	Never bill together
80184	Assay of phenobarbital	Never bill together
80185	Assay of phenytoin total	May bill with modifier
80186	Assay of phenytoin free	May bill with modifier
80188	Assay of primidone	May bill with modifier
80190	Assay of procainamide	May bill with modifier
80192	Assay of procainamide	May bill with modifier
80194	Assay of quinidine	May bill with modifier
80195	Assay of sirolimus	May bill with modifier
80197	Assay of tacrolimus	May bill with modifier
80198	Assay of theophylline	May bill with modifier
80199	Drug screen quant tiagabine	May bill with modifier
80200	Assay of tobramycin	May bill with modifier
80201	Assay of topiramate	May bill with modifier
80202	Assay of vancomycin	May bill with modifier
80203	Drug screen quant zonisamide	May bill with modifier
80320	Drug screen quantalcohols	May bill with modifier
80321	Alcohols biomarkers 1or 2	May bill with modifier
80322	Alcohols biomarkers 3/more	May bill with modifier
80323	Alkaloids nos	May bill with modifier
80324	Drug screen amphetamines 1/2	May bill with modifier
80325	Amphetamines 3or 4	May bill with modifier
80326	Amphetamines 5 or more	May bill with modifier
80327	Anabolic steroid 1 or 2	May bill with modifier
80328	Anabolic steroid 3 or more	May bill with modifier
80339	Antiepileptics nos 1-3	May bill with modifier
80340	Antiepileptics nos 4-6	May bill with modifier
80341	Antiepileptics nos 7/more	May bill with modifier

Showing 50 of 66 rules. Show all

FAQ — medical procedure bundling

What is NCCI bundling and what does 'bundled' mean on a medical bill?

NCCI bundling refers to the National Correct Coding Initiative rules that prevent certain procedure codes from being billed separately when performed together. When codes are bundled, one procedure is considered inclusive of another, meaning only the primary procedure should be billed rather than charging for each component separately.

How can I identify if codes were incorrectly unbundled on my bill?

Incorrectly unbundled codes appear as separate line items on your bill when NCCI rules indicate they should be grouped together under one primary procedure code. This typically occurs with anesthesia, radiology, pathology, and miscellaneous support services that are considered integral to the main procedure being performed.

What should I do if I find unbundled charges on my medical bill?

Contact your healthcare provider's billing department to request a review of the charges and provide documentation showing the NCCI bundling rules that apply. Request an itemized explanation of why the codes were billed separately and ask for a corrected bill that reflects proper bundling if no valid modifier justification exists.

When is it legitimate to use modifiers to override NCCI bundling rules?

Modifiers are appropriately used when procedures are performed on different anatomical sites, during separate patient encounters, or when distinct procedural services are provided that don't fall under the bundling restrictions. The modifier usage must be supported by clear documentation in the medical record that demonstrates the services were truly separate and distinct from the bundled procedure.

Rates shown are from the 2026 Medicare Physician Fee Schedule and CMS IPPS. BillRazor compares your bill against these data sources. See how it works →

Data source: CMS National Correct Coding Initiative (NCCI) Procedure-to-Procedure (PTP) edits, updated quarterly. These code pairs are maintained by CMS to prevent improper billing of services that should be billed as a single procedure.

What this means: When two codes are listed as an NCCI edit pair, billing them separately on the same date of service is typically incorrect. "Never bill together" means no modifier can override the rule. "May bill with modifier" means the codes can be billed separately with appropriate documentation.