I10 vs O11
I10 and O11 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
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)
O11
Pre-existing hypertension with pre-eclampsia
Not billable
- Chapter 15
- Pregnancy, childbirth and the puerperium
- Section
- O10-O16
Use when the record says
- conditions in O10 complicated by pre-eclampsia
- pre-eclampsia superimposed pre-existing hypertension
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