**I10 — Essential (primary) hypertension** is high blood pressure with no identifiable secondary cause. It is one of the most-coded conditions in primary care and the largest single risk factor for cardiovascular disease worldwide.
I10 is distinguished from secondary hypertension (I15.x), where high blood pressure results from a known underlying condition such as renal disease or endocrine disorder.
Belongs to **Chapter I** — Diseases of the circulatory system (I00-I99).
