Anesthesia Time Units: What They Are and How They're Inflated (2026)

The Anesthesia Billing Formula, Explained in Plain English

Most medical procedures are billed with a single CPT code — one procedure, one price. Anesthesia doesn't work that way. Anesthesia billing operates under a specialized, unit-based system that combines base units, which reflect procedural complexity, with time units that measure the actual minutes of anesthesia provided. The result is a formula that looks straightforward but has several moving parts a biller can quietly manipulate.

The governing federal regulation is 42 CFR § 414.46, "Additional rules for payment of anesthesia services." Under that rule, the fee schedule amount for an anesthesia service is based on the product of the sum of allowable base and time units multiplied by an anesthesia-specific conversion factor, and the carrier calculates time units from the anesthesia time reported by the anesthesia practitioner. That last phrase — "reported by the anesthesia practitioner" — is where errors and inflation enter the picture.

A "base unit" is the value assigned to each anesthesia code that reflects all activities other than anesthesia time, including usual preoperative and postoperative visits, the administration of fluids and blood incident to anesthesia care, and monitoring services. And "anesthesia time" means the time during which an anesthesia practitioner is present with the patient. Both of these definitions matter when you're reviewing a bill — because both can be inflated.

How the Numbers Actually Add Up: An Illustrative Scenario

(The following is a hypothetical illustrative example. All figures are based on published 2026 CMS rates and ASA base unit values for educational purposes only.)

Say you had a knee replacement (CPT 01402) at an outpatient surgery center in 2026. Your anesthesia bill shows a charge. How should that charge be calculated?

A total knee arthroplasty billed under CPT 01402 carries 7 base units. A 90-minute case adds 6 time units (90 ÷ 15 = 6). Seven plus six equals 13 total units. At the 2026 Medicare rate, that case pays roughly $266. Commercial payers set their own conversion factors, and those numbers tend to run considerably higher. The same 13 units billed to a commercial payer at a median conversion factor closer to $76 would pay closer to $988 — the same surgery, the same anesthesia time, but a nearly fourfold difference in payment.

Now suppose the bill instead shows 10 time units instead of 6 — an extra 60 minutes of claimed anesthesia time. At a commercial rate of $76 per unit, that's $304 in overcharges from time inflation alone. Multiply that across thousands of surgical cases and the dollar impact becomes enormous. Because anesthesia charges are calculated per minute or per 15-minute unit, even small errors in time reporting can result in hundreds of dollars in overcharges.

Illustrative only. Base units per ASA Relative Value Guide; commercial conversion factor used as median example. Your actual bill may use a different payer-contracted rate.

The Most Common Ways Anesthesia Bills Get Inflated

The most common billing irregularity cited in Medicare anesthesia audits is time-unit inflation: claiming more time units than the operative record supports. This can result from relying on estimated rather than documented start/stop times, from discrepancies between the anesthesia record and the OR circulating-nurse record, or from failure to adjust time when a handoff occurred mid-case.

Beyond time inflation, there are several other documented patterns. Assigning more base units than the ASA Relative Value Guide specifies for the procedure performed — for example, using the base units for a more complex procedure than what was actually done — directly inflates every unit calculation. There's also the concurrent-procedure double-billing problem: when multiple surgical procedures are performed during the same anesthesia session, only the highest base unit value should be used plus time for the entire session — billing base units for each procedure separately inflates the total.

A fourth documented pattern involves billing for a higher level of anesthesia than was actually used. Being billed for general anesthesia when only local or regional anesthesia was used — such as a nerve block — results in significantly higher charges because general anesthesia carries higher base units and typically longer time. HHS-OIG has specifically flagged a pattern in which anesthesia codes are billed alongside spinal pain management procedures where anesthesia is rarely indicated. HHS-OIG concluded that "Medicare could have saved an estimated $17.7 million if CMS's oversight had prevented at-risk payments for anesthesia administered during spinal pain management procedures." HHS-OIG's report noted that general anesthesia would be expected to be administered only 0.01% of the time for spinal pain management procedures.

What the 2026 Regulations Actually Require

The legal framework for anesthesia billing is anchored in several CFR provisions. 42 CFR § 414.46 sets out additional rules for payment of anesthesia services. 42 CFR § 415.110 sets conditions for payment of medically directed anesthesia services — which governs how an anesthesiologist is paid when a CRNA or anesthesiologist's assistant performs the hands-on work under supervision.

For the purpose of anesthesia time, "anesthesia practitioner" means a physician who performs the anesthesia service alone, a CRNA who is not medically directed who performs the anesthesia service alone, or a medically directed CRNA. The distinction matters for billing: different modifiers apply depending on who was physically present with you, and modifiers indicate the level of anesthesiologist supervision and accidental overbilling is watched closely by the Medicare Recovery Audit Contractor (RAC) program.

The final CY 2026 conversion factor for anesthesia is $20.4976 for most physicians , as finalized in the CY 2026 Physician Fee Schedule Final Rule (Federal Register, December 2025). CMS also finalized a separate conversion factor of $20.5998 for physicians participating in Advanced Alternative Payment Models (APMs). These are Medicare rates; commercial insurers set their own rates, which are typically much higher. If your bill shows a dollar amount, you can work backward through the formula — total billed amount ÷ conversion factor = total units claimed — and then verify whether those units are justified by the procedure code and the documented surgery time.

If you're unsure whether the charges on your anesthesia bill add up, reviewing your itemized hospital bill is the right starting point — it should show the anesthesia CPT code, the number of units billed, and the conversion factor applied.

How to Spot an Inflated Anesthesia Bill: A Step-by-Step Check

You don't need a medical degree to do a basic sanity check on your anesthesia charge. You need three things: your itemized bill, your operative report (which you can request from the hospital's medical records department), and about 15 minutes.

Start by locating the anesthesia CPT code on your itemized bill. Each anesthesia CPT procedure code from 00100 to 01999 has an assigned anesthesia base unit, and "base unit" means the value for each anesthesia code that reflects all activities other than anesthesia time. You can look up the assigned base unit value for your specific CPT code in the publicly available ASA Relative Value Guide or the CMS relative value file. If the billed base units don't match the published value for that code, that's a billing error.

Next, check the time. Your operative report will show a documented start time and stop time for anesthesia. Anesthesia time unit calculation divides total continuous anesthesia minutes by 15 to determine billable time units. If your procedure took 75 minutes but the bill shows 8 time units (120 minutes' worth), there's a 3-unit discrepancy — worth hundreds of dollars depending on your plan's conversion factor. Documentation mismatches are a known risk: inconsistent or incomplete records, especially around start and stop times, can jeopardize compliance and accuracy. If the anesthesia record and the OR nurse's record don't agree, that's exactly the kind of discrepancy you should flag in a dispute.

This type of billing error is related to a broader pattern of billing overcharges — if you haven't already, it's worth reading about how upcoding works across hospital billing to see how similar inflation tactics apply to other parts of your bill.

What to Do If Your Anesthesia Bill Looks Wrong

First, request your complete medical records including the anesthesia record and operative report. These are your property under HIPAA and must be provided to you. Then compare the documented times against what was billed. Groups should periodically reconcile anesthesia record times against OR information system data as a quality-assurance measure — and the same logic applies to you as the patient: the OR records are the ground truth.

If you find a discrepancy, submit a written dispute to both the billing provider and your insurer. Reference the specific line items by CPT code and the documented surgery times from your operative report. 42 CFR § 414.46 is the federal regulation that governs what can be charged; you can cite it directly in your dispute. For insured patients, your insurer also has an obligation to review claims for accuracy — you can ask them to audit the anesthesia claim specifically.

If the procedure involved a CRNA supervised by an anesthesiologist, check the modifiers. 42 CFR § 415.110 sets conditions for payment of medically directed anesthesia services , and the wrong modifier can mean you were billed at a higher "personally performed" rate when the actual service was medically directed at a lower rate. Also look at whether anesthesia was even appropriate for your procedure type. Medicare Administrative Contractors consistently indicate that moderate or deep sedation, general anesthesia, and monitored anesthesia care are typically considered unnecessary, not reasonable, and therefore not reimbursable for certain spinal pain management procedures.

For more on how phantom charges for services not rendered work and how to dispute them, the same dispute mechanics apply. And if your anesthesia bill has gone to collections before you had a chance to dispute it, review the federal rules on when a hospital can send you to collections — the CFPB has specific protections that may apply to your situation.

About VerifyDoc: We help patients identify errors and overcharges on medical bills. We publish guides on hospital billing, the No Surprises Act, and disputing medical charges, updated as federal and state rules change.