What's the difference between Excludes1 and Excludes2?
Excludes1 means two diagnosis codes can never go on the same claim, because both can't be true. Excludes2 means the conditions are different, so you code both when the patient has both.
By Alex, Chief Medical Officer
Excludes1 means two codes can never be billed together, because the two conditions can't both be true. Excludes2 means the other condition isn't part of this code, so when the patient has both, you code both.
Both notes sit in the ICD-10-CM tabular list, the official list of every diagnosis code, right under a code or category. They look alike on screen, and mixing them up costs money either way. Treat an Excludes1 pair like an Excludes2 and the claim can get denied or kicked back. Treat an Excludes2 like an Excludes1 and you leave off a condition the patient really has.
What does Excludes1 mean?
The official guidelines call Excludes1 "a pure excludes note," meaning the other condition is never coded here. The excluded code "should never be used at the same time as the code above the Excludes1 note." It's used when two conditions can't happen together, like an inborn and an acquired form of the same problem.
Think of the two codes as two answers to one question. A patient's diabetes is type 1 or type 2. Their depression is a single episode, or it keeps coming back. They smoke now, or they used to. The chart can give only one answer, so the claim can carry only one code.
What does Excludes2 mean?
Excludes2 means "Not included here." The guidelines say the excluded condition "is not part of the condition represented by the code, but a patient may have both conditions at the same time." When both are true and both matter to the visit, both codes go on the claim.
Read Excludes2 as a pointer. It tells you this code doesn't cover the other condition, so look it up under its own code instead of assuming it's included.
What do Excludes1 and Excludes2 look like on real codes?
Several categories that primary care uses every week carry both kinds of note, which makes the difference easy to see. Every note below comes from the FY2027 ICD-10-CM tabular list, in effect October 1, 2026 through September 30, 2027.
| If the claim has | Excludes1: never on the same claim | Excludes2: code both when both are true |
|---|---|---|
| J01.- Acute sinusitis | J32.9 Chronic sinusitis, unspecified (where plain "sinusitis" lands) | J32.0–J32.8 Chronic sinusitis of a named sinus, such as J32.0 chronic maxillary sinusitis |
| I12.- Hypertensive chronic kidney disease | I15.0 Renovascular hypertension | N17.- Acute kidney failure |
| R10.- Abdominal and pelvic pain | N23 Unspecified renal colic | M54.- Back pain |
| J45.- Asthma | R06.2 Wheezing | J44.89 Other specified COPD, where asthma with COPD is coded |
| F32.- Depressive episode | F33.- Recurrent depression | |
| R73.- Elevated blood glucose, including R73.03 prediabetes | E08–E13 Diabetes | |
| Z87.891 History of nicotine dependence | F17.2- Current nicotine dependence |
Take the kidney row. I12.9 says high blood pressure damaged the kidneys. I15.0 says narrowed kidney arteries drove the blood pressure up. Those are opposite stories about cause, so only one can go on the claim. A patient with hypertensive kidney disease who also has an acute kidney injury this week is a different case. The injury is a new problem on top of the old one, so I12.9, the stage code, and N17.9 all belong.
The sinus row works the same way. Acute sinusitis on top of a known chronic maxillary sinusitis gets J01.00 and J32.0. Acute sinusitis next to J32.9 is a conflict, and it usually means a vague "sinusitis" entry is sitting on the problem list.
How does an Excludes1 pair end up on a claim?
Usually through the problem list, the running list of a patient's diagnoses in the chart. Here's how it happens with prediabetes:
- In March, the patient's A1c is 6.1%. The doctor adds R73.03, prediabetes, to the problem list.
- In September, a repeat A1c comes back at 7.2%, and the doctor diagnoses type 2 diabetes. E11.9 goes on the list. Nobody resolves the prediabetes entry.
- At the November visit for blood pressure and diabetes, both codes ride from the problem list onto the claim.
R73's Excludes1 note covers every diabetes code from E08 through E13. The claim now says the patient has diabetes and also a blood sugar that falls short of diabetes. An insurance company that runs Excludes1 edits can deny the claim line or send the whole claim back.
The fix takes a minute. Resolve R73.03 on the problem list, keep E11.9 or the more specific diabetes code the note supports, and send the claim. Caught before the claim goes out, it costs nothing. Caught after a denial, it's a correction, a resubmission, and a few more weeks of waiting on the money. See what that rework costs.
The same thing happens when a former smoker starts again and Z87.891 stays next to F17.210, or when a second episode makes depression recurrent and the old F32 code stays next to the new F33 code.
When can you code both sides of an Excludes1 note?
Only when the two conditions are unrelated. Guideline I.A.12.a makes that one exception and gives its own example. F45.8, other somatoform disorders, has an Excludes1 note for G47.63, sleep related teeth grinding, because teeth grinding is listed under F45.8. But F45.8 also covers psychogenic dysmenorrhea. A patient with psychogenic dysmenorrhea and sleep related teeth grinding has two unrelated problems, so both codes are correct.
If it's not clear whether the two conditions are related, the guideline says to query the provider, meaning ask the clinician who wrote the note. The exception never rescues a leftover problem-list code. Prediabetes and diabetes are the same blood sugar story told twice, so only one belongs.
Do insurance companies check Excludes1?
Yes, and more of them check automatically, before a person reads the note. UnitedHealthcare Medicare Advantage began applying Excludes1 to professional claims on March 1, 2026. See how that edit and two other payer rules work. Each payer sets its own edits, so check your plans' policies. The guideline itself applies to every claim, because the ICD-10-CM codes and guidelines are adopted under HIPAA for all healthcare settings.
Excludes2 pairs don't break the rule. If a payer denies one, ask for a review and cite the tabular note.
How do you catch these before the claim goes out?
ICD-10-CM has more than 5,000 Excludes1 rules, far more than anyone can memorize. Two habits catch most of the pairs that reach primary care claims:
- When a new diagnosis replaces an old one, resolve the old entry the same day. Prediabetes, history-of codes, and single-episode depression are the usual leftovers.
- Before the claim goes out, read the diagnosis codes as a set and ask whether any two tell different stories about the same condition.
Both checks fit into the review before a chart is signed.
Cortex Lens checks every Practice Fusion chart against the full Excludes1 table before the claim goes out. When two codes can't be billed together, it shows both codes and the rule, and your team picks the one the note supports.
Sources: Excludes1 and Excludes2 definitions, the unrelated-conditions exception, and HIPAA adoption: CMS and NCHS, ICD-10-CM Official Guidelines for Coding and Reporting, FY2027, Section I.A.12 and the introduction, effective October 1, 2026 through September 30, 2027. Excludes notes for each code in the table: FY2027 ICD-10-CM tabular list. Rule count: the Excludes1 notes from the CDC's ICD-10-CM release files. UnitedHealthcare's Excludes1 enforcement: UnitedHealthcare Medicare Advantage reimbursement policy bulletin, February 2026.