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I16.1 vs O10

I16.1 (Hypertensive emergency) compared with O10 (Pre-existing hypertension complicating pregnancy, childbirth and the puerperium), from the official CMS tabular data.

Summary

These codes can be reported together when both conditions are documented, because I16.1 lists O10 under Excludes2, which marks them as distinct conditions.

Official rule
What is different?

The conditions named, billing status and chapter.I16.1 is “Hypertensive emergency”; O10 is “Pre-existing hypertension complicating pregnancy, childbirth and the puerperium”. O10 is a non-billable header; I16.1 is billable. I16.1 sits in I00-I99 — Diseases of the Circulatory System (I00-I99); O10 in O00-O9A — Pregnancy, Childbirth and the Puerperium (O00-O9A).

Registry fact

Can these codes be reported together?

Yes, when both are documented.I16.1 lists O10 under Excludes2: “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”. Excludes2 marks distinct conditions that may both be reported when both are documented.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

None.Neither entry carries an Excludes1 note that names the other code. I16.1 carries 2 Excludes1 notes covering other codes; the side-by-side table quotes them.

Official rule

Is there an Excludes2 relationship?

Yes.I16.1’s tabular entry: “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”. The note covers O10.

Official ruleGuide: Excludes1 vs Excludes2

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

One is a header.O10 is a non-billable header, but I16.1 is not one of its subdivisions.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Informational

Excludes2 relationship

I16.1
Hypertensive emergency
↔
O10
Pre-existing hypertension complicating pregnancy, childbirth and the puerperium

What we found

Yes, when both are documented.I16.1 carries an Excludes2 note covering O10: “hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)”

Excludes2 marks distinct conditions — both may be reported when both are documented.

What to review

Report both only when the documentation supports both conditions; otherwise report the one documented.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes2 note means the excluded condition is not part of the code above it, but a patient can have both. Report both when both are documented.

Source / rule

CMS ICD-10-CM tabular instructional notes

Official guidance behind these answers

  • Section I.A.12.b — Excludes2 · applies to: Excludes2

    A type 2 Excludes note represents “Not included here.” An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.

    ICD-10-CM Official Guidelines FY2026

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

I16.1Hypertensive emergencyO10Pre-existing hypertension complicating pregnancy, childbirth and the puerperium
Billing statusBillableNon-billable header

Report instead: O10.011, O10.012, O10.013, O10.019, O10.02

ClassificationI00-I99 — Diseases of the Circulatory System (I00-I99)O00-O9A — Pregnancy, Childbirth and the Puerperium (O00-O9A)
DefinitionHypertensive emergency is a billable ICD-10-CM diagnosis code (I16.1).Pre-existing hypertension complicating pregnancy, childbirth and the puerperium is a non-billable ICD-10-CM category code (O10).
Includes—
pre-existing hypertension with pre-existing proteinuria complicating pregnancy, childbirth and the puerperium
Excludes1
neonatal hypertension (P29.2)
primary pulmonary hypertension (I27.0)
—
Excludes2
hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)
pre-existing hypertension with superimposed pre-eclampsia complicating pregnancy, childbirth and the puerperium (O11.-)
Use additional code
code to identify:
exposure to environmental tobacco smoke (Z77.22)
history of tobacco dependence (Z87.891)
—
Code also
, if applicable, to identify specific organ dysfunction, such as:
acute kidney injury (N17.-)
acute myocardial infarction (I21.-)
acute pulmonary edema (left and/or right ventricular failure) (J81.0, I50.-)
aortic dissection (I71.0-)
cerebral hemorrhage (I60.-. I61.-, I62.-)
cerebral infarction (I63.-)
eclampsia (O15.-)
hypertensive encephalopathy (I67.4)
seizure (R56.9)
any identified hypertensive disease (I10-I15, I1A)
—

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources