FY2027
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Excludes1 pair

I10 vs O16-

I10 and O16 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.

The official note, declared on I10
hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)
I10

Essential (primary) hypertension

Billable
Chapter 9
Diseases of the circulatory system
Section
I10-I1A
Use when the record says
  • high blood pressure
  • hypertension (arterial) (benign) (essential) (malignant) (primary) (systemic)
Indexed under
  • Hypertension, hypertensive (accelerated) (benign) (essential) (idiopathic) (malignant) (systemic)
O16

Unspecified maternal hypertension

Not billable
Chapter 15
Pregnancy, childbirth and the puerperium
Section
O10-O16

These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.

Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027