ICD Coding for Hypertension
Hypertension is coded in the ICD system using a hierarchical approach that distinguishes between primary (essential) hypertension and secondary hypertension, with additional codes for complications and associated conditions.
Basic ICD-10 Coding Structure
The ICD-10 classification system uses the following primary codes for hypertension:
- I10: Essential (primary) hypertension - This is the most commonly used code for uncomplicated hypertension without a known secondary cause 1
- I11: Hypertensive heart disease - Used when hypertension has caused cardiac complications 2
- I12: Hypertensive chronic kidney disease - Applied when hypertension has resulted in renal damage 3
- I13: Hypertensive heart and chronic kidney disease - For combined cardiac and renal involvement 2
- I15: Secondary hypertension - Used when hypertension results from an identifiable underlying cause 3
Coding by Blood Pressure Severity
While ICD codes don't directly classify by blood pressure levels, clinical staging informs documentation:
- Stage 1 hypertension: Systolic 130-139 mmHg or diastolic 80-89 mmHg in adults 4
- Stage 2 hypertension: Systolic ≥140 mmHg or diastolic ≥90 mmHg in adults 4
- Severe hypertension: Systolic ≥180 mmHg or diastolic ≥100 mmHg 5
For pediatric patients, hypertension is defined as measurements at or above the 95th percentile for gender, age, and height on 3 or more occasions, with stage 1 and stage 2 classifications based on proximity to the 99th percentile 1
Coding for Complicated vs. Uncomplicated Hypertension
The presence of target organ damage or cardiovascular risk factors fundamentally changes coding:
- Uncomplicated hypertension: Use I10 when no target organ damage, cardiovascular disease, or other complications are present 6
- Complicated hypertension: Use specific codes (I11-I13) when target organ damage exists, including left ventricular hypertrophy, proteinuria with albumin/creatinine ratio ≥30 mg/g, or established cardiovascular disease 2, 6
More than 50% of hypertensive patients have additional cardiovascular risk factors that should be documented with separate codes 3
Secondary Hypertension Coding
When hypertension results from an identifiable cause, use I15 codes with additional codes for the underlying condition 3:
- Primary aldosteronism (presenting with hypokalemia)
- Pheochromocytoma (with blood pressure lability)
- Cushing's syndrome (with characteristic physical findings)
- Hyperthyroidism
- Obstructive sleep apnea
- Drug-induced hypertension (NSAIDs, cocaine, amphetamines, corticosteroids)
Hypertensive Emergency vs. Urgency
Critical distinction for coding:
- Hypertensive emergency: Substantially elevated blood pressure WITH acute target organ damage requires specific coding for both the hypertension and the acute organ damage 5
- Severe asymptomatic hypertension: Blood pressure ≥180/100 mmHg WITHOUT symptoms or acute organ damage is coded as I10, not as an emergency 5
Common Coding Pitfalls
Avoid under-coding by missing complications: ECG has only 10-30% sensitivity for detecting left ventricular hypertrophy, while echocardiography has 80-90% sensitivity 2. Failure to perform appropriate diagnostic testing may result in coding uncomplicated hypertension when complications actually exist.
Document all cardiovascular risk factors separately: Among U.S. adults with hypertension, 41.7% have a 10-year coronary heart disease risk >20%, and these additional risk factors require separate ICD codes 3
Use sex-specific thresholds: Consider sex-specific diagnostic criteria to avoid under-diagnosis in women, which affects appropriate coding 2
Coding for Associated Conditions
Document separately with additional codes 3:
- Diabetes mellitus (present in 15-20% of hypertensive patients)
- Dyslipidemia (30% of patients)
- Metabolic syndrome (40% of patients)
- Chronic kidney disease (15.8% of patients)
- Obesity (40% of patients)