Chapter 9: - Disease of Cardiovascular System (I00-I99)
Hypertension
Introduction
Blood pressure is the pressure exerted by flowing blood on the wall of vessels.
Normal blood pressure is 120/80 mmHG.
120 mmHg is the systolic blood pressure — the pressure in the blood vessels when the ventricles are at the peak of contraction.
80 mmHg is the diastolic blood pressure — the pressure in the blood vessels when the ventricles are at the peak of relaxation.
In medical terms, hypertension is typically defined as blood pressure readings of 130/80 mmHg or higher according to US guidelines from organizations like the American Heart Association (AHA), or 140/90 mmHg or higher according to the World Health Organization (WHO).
Affecting an estimated 120 million adults in the US and 1.28 billion globally, hypertension is a major risk factor for heart disease, stroke, kidney disease, and other complications.
Coding Guidelines - HYPERTENSION (HTN)
Hypertension is coded with I10.
Other non-essential modifier for hypertension, Accelerated, Benign, essential, Idiopathic, malignant, systemic does not change the code.
Benign HTN is coded with I10
Essential HTN is coded with I10
The classification presumes a causal relationship between hypertension and heart involvement and between hypertension and kidney involvement, as the two conditions are linked by the term “with” in the Alphabetic Index. These conditions should be coded as related even in the absence of provider documentation explicitly linking them, unless the documentation clearly states the conditions are unrelated.
For hypertension and conditions not specifically linked by relational terms such as “with,” “associated with” or “due to” in the classification, provider documentation must link the conditions in order to code them as related.
HYPERTENSION WITH HEART DISEASE
Hypertension with heart conditions classified to I50.- or I51.4- I51.7, I51.89, I51.9, are assigned to a code from category I11, Hypertensive heart disease. Use additional code(s) from category I50, Heart failure, to identify the type(s) of heart failure in those patients with heart failure.
Not all heart disease with HTN is coded with I11._ series except classified to below
I50: - Heart Failure
I51.4: - Myocarditis, unspecified
I51.5: - Myocardial degeneration
I51.7: -Cardiomegaly
I51.89: -Other ill-defined heart diseases
I51.9: - Heart disease, unspecified
The same heart conditions (I50.-, I51.4-I51.7, I51.89, I51.9) with hypertension are coded separately if the provider has documented they are unrelated to the hypertension. Sequence according to the circumstances of the admission/encounter.
Patient has hypertension and heart failure. Heart failure is due to prior myocardial infarction, not related to hypertension."
ICD-10-CM Codes:
I10 – Essential (primary) hypertension
I50.9 – Heart failure, unspecified
Explanation: The provider states the conditions are not related, so code them separately.
HYPERTENSIVE CHRONIC KIDNEY DISEASE
HTN and CKD if both present in the diagnostic statement, or one is in PMH and other in A/P, ICD 10 CM presumes there cause-and-effect relation according to the guideline as these 2 conditions are linked by the term "with" alphabetical index and should be coded be related even in absence of provider's documentation explicitly linking them, unless the documentation clearly states the conditions are unrelated.
When a patient has both hypertension and chronic kidney disease, ICD-10-CM assumes they are related, even if the provider does not say so.
In this case, assign a code from category I12 (Hypertensive chronic kidney disease).
Use a 4th character in the I12 code to show the stage of CKD.
Also, add a code from category N18 to specify the CKD stage.
Example: - Hypertensive CKD
PDX I12.9: Hypertensive chronic kidney disease with stage 1 through stage 4 chronic kidney disease, or unspecified chronic kidney disease
Additional Dx: I12.9
Hypertension with Acute Kidney Failure
Acute kidney failure is different from chronic kidney disease and is not caused by hypertension.
Do not assign an I12 code for this situation.
Instead, code them separately.
Example: The patient was admitted due to acute kidney failure with renal papillary necrosis caused by NSAID use. The patient also has a history of essential hypertension, well-controlled with medication.
N17.2 – Acute kidney failure with medullary necrosis
I10 – Essential hypertension
If a patient has hypertensive chronic kidney disease and acute renal failure, both conditions should be coded. Sequencing is decided based on the reason for the admission or encounter.
example: The patient presents with acute kidney injury due to dehydration, superimposed on chronic hypertensive nephropathy. CKD stage 3 is known. Patient also has long-standing essential hypertension.
N17.9 – Acute kidney failure, unspecified
I12.9 – Hypertensive CKD with stage 1–4 or unspecified
N18.3 – CKD stage 3
Coding Tip: Include instructions of I12 _ Hypertensive Nephropathy & Nephrosclerosis
🤔 What does "Includes" mean?
In ICD-10-CM, an “Includes” note means that the listed conditions are part of the main code. So, if a condition is listed under an “Includes” note, you don’t need a separate code for it — it’s already covered!
What to Do If the Provider Documents:
🩺 Example 1. Hypertensive Nephropathy
Scenario:
A patient is diagnosed with hypertensive nephropathy and has chronic kidney disease (CKD) stage 3.
How to code it:
I12.9 – Hypertensive chronic kidney disease with stage 1 through stage 4, or unspecified
N18.30 – CKD stage 3
🧠 Why? “Hypertensive nephropathy” is listed in the Includes note under I12, so it’s automatically considered a hypertensive CKD condition. Always add a code to show the CKD stage (from N18.- series).
🩺 Example 2. Hypertensive Nephrosclerosis
Scenario:
A patient has a diagnosis of hypertensive nephrosclerosis with CKD stage 4.
How to code it:
I12.9 – Hypertensive chronic kidney disease (stage 1–4 or unspecified)
N18.4 – CKD stage 4
🧠 Why? “Hypertensive nephrosclerosis” is also listed in the Includes note under I12.9, so it’s coded the same way. And don’t forget — always show the stage of CKD.
Examples Without CKD Stage Documentation
🩺 Example 3: hypertensive nephropathy
Provider Note:
"Patient has a history of hypertensive nephropathy."
Code this as:
I12.9 – Hypertensive CKD with stage 1–4 or unspecified
🧠 Why?
Even though CKD is implied by "nephropathy," the stage isn't documented. You can still report I12.9, but do not assign a code from N18.- unless the stage is clearly stated.
🩺 Example 4: Hypertensive nephrosclerosis
Provider Note:
"Hypertensive nephrosclerosis is noted, likely contributing to declining kidney function."
Code this as:
I12.9 – Hypertensive CKD with stage 1–4 or unspecified
🧠 Why?
The documentation supports a hypertensive CKD relationship, but without a specific CKD stage, you must stop at I12.9.
🩺 Example 5:
Provider Note:
"Patient with chronic hypertension and renal disease."
Code this as:
I12.9 – Hypertensive CKD with stage 1–4 or unspecified
🧠 Why?
The term "renal disease" is vague, but when paired with "chronic hypertension," it’s appropriate to use I12.9. Still, do not assume the stage unless it's stated.
🔍 Coding Tip:
When stage is not documented, use only I12.9.
Never guess or assign a CKD stage based on lab values unless the provider documents it.
If CKD stage is missing, query the provider if possible.
HYPERTENSIVE HEART AND CHRONIC KIDNEY DISEASE
Assign codes from combination category I13, Hypertensive heart and chronic kidney disease, when there is hypertension with both heart and kidney involvement. If heart failure is present, assign an additional code from category I50 to identify the type of heart failure.
The appropriate code from category N18, Chronic kidney disease, should be used as a secondary code with a code from category I13 to identify the stage of chronic kidney disease.
The codes in category I13, Hypertensive heart and chronic kidney disease, are combination codes that include hypertension, heart disease and chronic kidney disease. The Includes note at I13 specifies that the conditions included at I11 and I12 are included together in I13. If a patient has hypertension, heart disease and chronic kidney disease, then a code from I13 should be used, not individual codes for hypertension, heart disease and chronic kidney disease, or codes from I11 or I12.
For patients with both acute renal failure and chronic kidney disease, the acute renal failure should also be coded. Sequence according to the circumstances of the admission/encounter.
HYPERTENSIVE HEART AND CHRONIC KIDNEY DISEASE
HYPERTENSIVE CEREBROVASCULAR DISEASE
For hypertensive cerebrovascular disease, first assign the appropriate code from categories I60-I69, followed by the appropriate hypertension code.
HYPERTENSIVE RETINOPATHY
subcategory H35.0, Background retinopathy and retinal vascular changes, should be used along with a code from categories I10 – I15, in the Hypertensive diseases section, to include the systemic hypertension. The sequencing is based on the reason for the encounter.
HYPERTENSION, SECONDARY
Secondary hypertension is due to an underlying condition. Two codes are required: one to identify the underlying etiology and one from category I15 to identify the hypertension. Sequencing of codes is determined by the reason for admission/encounter.
HYPERTENSION, TRANSIENT
Assign code R03.0, Elevated blood pressure reading without diagnosis of hypertension, unless patient has an established diagnosis of hypertension. Assign code O13.-, Gestational [pregnancy-induced] hypertension without significant proteinuria, or O14.-, Pre-eclampsia, for transient hypertension of pregnancy
HYPERTENSION, CONTROLLED
This diagnostic statement usually refers to an existing state of hypertension under control by therapy. Assign the appropriate code from categories I10-I15, Hypertensive diseases.
HYPERTENSION, UNCONTROLLED
Uncontrolled hypertension may refer to untreated hypertension or hypertension not responding to current therapeutic regimen. In either case, assign the appropriate code from categories I10-I15, Hypertensive diseases.
HYPERTENSIVE CRISIS
Assign a code from category I16, Hypertensive crisis, for documented hypertensive urgency, hypertensive emergency or unspecified hypertensive crisis. Code also any identified hypertensive disease (I10- I15). The sequencing is based on the reason for the encounter.
PULMONARY HYPERTENSION
Pulmonary hypertension is classified to category I27, Other pulmonary heart diseases. For secondary pulmonary hypertension (I27.1, I27.2-), code also any associated conditions or adverse effects of drugs or toxins. The sequencing is based on the reason for the encounter, except for adverse effects of drugs.
HYPERTENSION RESISTANT
Resistant hypertension refers to blood pressure of a patient with hypertension that remains above goal in spite of the use of antihypertensive medications. Assign code I1A.0, Resistant hypertension, as an additional code when apparent treatment resistant hypertension, treatment resistant hypertension, or true resistant hypertension is documented by the provider. A code for the specific type of existing hypertension is sequenced first, if known.
Practice Questions on Hypertension
Atherosclerotic Coronary Artery Disease and Angina
Coronary Artery
Atherosclerosis
Angina Pectoris
Intraoperative and Postprocedural Cerebrovascular Accident
Sequelae of Cerebrovascular Disease
Category I69, Sequelae of Cerebrovascular disease
Codes from category I69 with codes from I60-I67
Codes from category I69 and Personal history of transient ischemic attack (TIA) and cerebral infarction (Z86.73)
Acute myocardial infarction (AMI)
Type 1 ST elevation myocardial infarction (STEMI) and nonST Elevation myocardial infarction (NSTEMI)
Acute myocardial infarction, unspecified
AMI documented as nontransmural or subendocardial but site provided
Subsequent acute myocardial infarction
Other Types of Myocardial Infarction
Myocardial Infarction with Coronary Microvascular Dysfunction