What is an MUE and how do you avoid MUE denials?
A medically unlikely edit (MUE) is the most units of one code Medicare expects for one patient on one date of service. You avoid the denial by checking units against the right CMS table and quarter before the claim leaves, counting in the code's own unit.
Written by Salman Saeed, CEO and Co-Founder · Reviewed by a Certified Medical Coder · 
In short: an MUE caps the units of one code per patient per date of service, and the indicator decides whether lines are counted alone or added together. Check the table, quarter and unit definition before sending, and fix keyed-wrong units by reopening, not by splitting lines.
What do you check before each claim goes out?
How does the manual say to count units?
The NCCI Policy Manual says a provider shall not report units using a criterion that differs from the code's defined unit of service. It gives therapy as an example: some therapy codes are counted in fifteen-minute increments and others per session, and a per-session code must not be reported in fifteen-minute increments. The medicine chapter adds more rules of the same kind.
| Code family | How the manual counts units |
|---|---|
| Antigen preparation, 95145 to 95170 | Number of doses, with one dose defined as 1 ml. A 10 ml vial is reported as at most 10 units, even if more doses were given. |
| Group psychotherapy, 90849 and 90853 | Each separate session, not a time interval. A practitioner reports one unit on a date of service. |
| Hemodialysis, 90935 and 90937 | One unit for a single session. |
| Audiologic function tests, 92550 to 92588 | One unit covers both ears. If only one ear is tested, report the code with modifier 52. |
| Bilateral surgical procedures | Practitioners and outpatient hospitals report one unit with modifier 50 unless the descriptor says bilateral. An ambulatory surgical center reports two lines of one unit, with LT and RT. |
| Allergy testing by number of tests | Count the tests. Positive and negative controls are not counted. |
The same chapter warns about reporting a code on several lines with modifiers to get past an MUE. If a provider does this often for a code, CMS says the units may be coded incorrectly, and it suggests asking the national society for that procedure how to report them.
Can you predict a limit from the code descriptor?
Often, yes. Chapter I lists the reasons CMS sets a value, and several are visible in the descriptor itself. Reading it before you key units catches many errors at charge entry.
| Words in the descriptor | What the manual says about the value |
|---|---|
| Initial 30 minutes | Value of 1, because a different code reports additional time. |
| A plural, such as biopsies | Report one unit regardless of how many were done. |
| Per day, per week or per month | Value of 1, because MUEs are based on services per date of service. |
| Unilateral, with a separate bilateral code | Value of 1. |
| An overnight or long-running procedure | Value of 1 because of the time the procedure takes. |
A value of 0 is possible too. The manual says CMS can set 0 when a code is invalid, not covered, bundled or not separately payable.
Why are anesthesia minutes not compared with an MUE?
Chapter 26 of the Medicare Claims Processing Manual tells the biller to show anesthesia elapsed time in minutes in item 24G of the CMS-1500, converting hours to minutes. That field is not a unit count in the MUE sense. In the Q4 2026 practitioner table, the only code in the anesthesia section (00100 to 01999) listed is 01996, daily management of epidural or subarachnoid drug administration, with a value of 1 and an indicator of 2.
The anesthesia chapter of the NCCI manual says payment for that management is limited to one unit of service per day, whatever the number of visits. Billing 01996 twice on one date is therefore a policy denial that no appeal wins back, since MAI 2 edits are not overridden. Other codes the same practitioner bills that day are still checked against their own values. See the anesthesia billing page for the specialty.
What do you do when an MUE denial arrives?
- Find the denied line and the code. The reason code is chosen by the payer, so start from the remark text rather than the group code.
- Count the units against the right table, quarter and indicator.
- If the units were keyed wrong, ask for a reopening. If they were correct and the indicator is 1 or 3, appeal with the records. If the indicator is 2, correct the claim instead of appealing for more units.
- Do not bill the patient. The manual says an ABN does not shift liability for units denied on an MUE.
A CO-97 or CO-4 on the same remit can have a different cause, such as a code pair or a modifier. See the CO-97 page and the CO-4 page, and how to read NCCI edits for pair edits. The NCCI edits page holds the appeal deadlines.
What does a units check catch?
A practice prepares a 10 ml antigen vial and keys 12 as the units because 12 doses were given. The manual caps the units for that vial at 10.
How Nucleus Align handles units
Our medical coding team checks units against the quarter's CMS table before claims are sent, and we send claims within 24 hours of charge entry. To see how that would work for your claims, book a call.
- Medicare NCCI Policy Manual for Medicare Services, 2026 (all chapters) · CMS
- Medicare NCCI Medically Unlikely Edits (MUEs) · CMS
- Practitioner Services MUE table, effective October 1, 2026 · CMS
- Medicare Claims Processing Manual, chapter 26, item 24G · CMS
- Medicare NCCI FAQ Library · CMS
We check every rule, code and deadline against the official source. See our editorial policy.
Common questions
Straight answers from the team that does the work.
Ask a billing lead directly. A 20-minute call, Monday to Friday, 9am to 5pm Eastern.
01What is an MUE and how do you avoid MUE denials?
An MUE is the most units of one code that Medicare expects for one patient on one date of service. Avoid denials by checking units against the right CMS table and quarter before the claim goes out, counting in the code's own unit, and adding up every line of the same code.
02Is an MUE the same as an NCCI procedure-to-procedure edit?
No. An MUE limits the units of a single code on one date of service. A procedure-to-procedure edit pairs two different codes reported together. Both belong to NCCI, and one claim can hit either, so read the remark text on the remit before choosing a fix.
03Can you add a modifier to get past an MUE?
Only on an MAI 1 edit, where modifiers such as 59, 76, 77, 91 or an anatomic modifier may report the same code on separate lines. On MAI 2 and 3 the lines are added together. Using a modifier only to get past a limit is not allowed.
04Do anesthesia minutes count against an MUE?
Not in the Q4 2026 practitioner table. Anesthesia time goes in item 24G in minutes, and the only code in the anesthesia section listed there is 01996, with a value of 1 and an indicator of 2. Other codes on the claim are still checked.
05Can you bill the patient for units an MUE denies?
No. The NCCI Policy Manual says an MUE denial is a coding denial, not a medical necessity denial, and an ABN does not shift liability to the beneficiary. Correct the claim or appeal, then write off units that stand denied.
Talk to a billing lead.
A 20-minute call about your payers, volume and setup. Monday to Friday, 9am to 5pm Eastern.