CPT 94729: DLCO (diffusing capacity)
What this code means, what it should cost, and how to dispute an overcharge.
Fair Price Reference
What is CPT 94729?
CPT 94729 (DLCO (diffusing capacity)) is a pulmonary billing code defined by the American Medical Association. It's used to bill your insurance or you directly for this service.
What CPT 94729 should cost
The Centers for Medicare & Medicaid Services (CMS) pays approximately $22 for CPT 94729 under the 2025 Physician Fee Schedule. This is what the federal government has determined is a reasonable payment for this service.
Private insurance typically pays 1.2–1.8x Medicare rates ($26–$40). Hospital chargemaster prices for CPT 94729 often range from $50 to $250 — a markup of 2.3x to 11.4x over Medicare.
Common overcharges on CPT 94729
Billing individual components (spirometry, diffusing capacity, plethysmography) when a complete pulmonary function study code should apply. Billing sleep studies with components separately.
About Pulmonary billing
Pulmonary function tests have complex bundling rules. Individual components are frequently billed when a comprehensive code applies.
Compare billed codes against CPT bundling rules. Request the PFT report to confirm which tests were actually performed.
How to dispute a CPT 94729 overcharge
- Request the itemized bill. You are entitled to a detailed line-by-line bill showing every CPT code billed. Ask in writing.
- Compare to Medicare allowable. If the charge exceeds 150% of Medicare ($33), you have grounds to dispute.
- Request documentation. For E&M codes, ask for the visit note. For procedures, ask for the operative report. The documentation must justify the code billed.
- Send a formal dispute letter. Cite the specific discrepancy between the documentation and the code. Reference Medicare rates and NCCI edits where applicable.
- Follow up in writing. Give the provider 30 days to respond. If they don't, escalate to the state attorney general and insurance commissioner.
Got CPT 94729 on your bill?
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