Understanding How & When to Code Hypertension

We hear so much in the news and from healthcare practitioners concerning the importance of maintaining a normal blood pressure. Often times, coders lack the understanding of the lingo and terminology used so they can correctly decipher the physician’s documentation. Unfortunately, ICD-9-CM was written in the 1970s, so even when a coder understands the terminology, some of it is outdated. With the prevalence of hypertension in the U.S., more and more patients are presenting with hypertension and/or a hypertensive-related disease. With this increase also comes an increase in the importance of accurate coding.

Let’s begin by looking at some of the more common definitions surrounding hypertension.

What is Blood Pressure & Hypertension?
Blood pressure is the force of the blood pushing against the walls of the arteries as the heart pumps blood. When reading a blood pressure, the top number represents the systolic pressure and the bottom number represents the diastolic pressure. Systolic blood pressure indicates the pressure in the arteries as the heart beats while pumping blood, whereas, diastolic refers to blood pressure when the heart is relaxed between beats. A normal blood pressure as defined by the American Heart Association should be less than 120/80 in adults ages 20 and older.

The term high blood pressure is frequently used in the healthcare field synonymously with hypertension; however, as coders we are not allowed to code high blood pressure as hypertension unless the physician documents it. A person’s blood pressure can be high due to various reasons including stress and exercise (transient). A physician will often monitor a person’s blood pressure over a period of time before making the diagnosis of hypertension.

Hypertension is the increase of pressure in the arteries, which can vary in the degree of severity, dependent on the level of the blood pressure reading.

Another set of terms used synonymously is accelerated and malignant hypertension. These are very similar conditions, except on examination malignant hypertension will show actual swelling of the brain and papilledema. As a coder, you can only code malignant (or accelerated) hypertension with the support of documentation. Benign hypertension is a long-standing, symptomless hypertension, which is also coded with the support of documentation from the physician.

In the world of chronic insufficient documentation, coders are left to code what is documented, which frequently is simply unspecified hypertension. Many physicians refer to hypertension as being controlled and/or uncontrolled. Controlled hypertension normally references a known state of hypertension that is currently being controlled by drug therapy. Uncontrolled hypertension indicates either untreated hypertension, hypertension that is not responding to current therapy, or a patient who is non-compliant with treatment prescribed. Unfortunately, in ICD-9-CM, there is not a specific code for either controlled or uncontrolled hypertension, so the appropriate code from categories 401-405 is used to designate the stage and type of hypertension.

Before we review the specific codes and coding guidelines for hypertension, let’s look at the hypertension table.

The Hypertension Table
Looking at the hypertension table for the first time, I felt like I was staring at some sort of game. I kept thinking I would never understand how to interpret the table. After years of coding, I have learned the important keys in coding hypertension include understanding hypertensive terminology, the coding guidelines and the hypertension table. With encoders being the most popular means of coding, it can cause a coder to forget how to use the book. However, when taking the CCS exam, code books, not the encoder are used, so it is important to understand how to read the hypertension table.

Below is a portion of the hypertension table for reference. The key to understanding the table is determining from documentation and the guidelines if there is a hypertensive manifestation (e.g., chronic renal failure or heart disease). Next, the coder needs to read the record and note if the hypertension is malignant, benign or unspecified per the physician’s documentation. The last step concerns whether or not the hypertensive condition is linked to another condition in the medical record.

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Remember the words in parentheses are non-essential modifiers, which represent supplementary words that may be present or absent in the statement of hypertension without affecting the code number. For example, the documentation states fluctuating hypertension, since fluctuating is a non-essential modifier and there is not any documentation of any type of manifestation or malignant/benign status, the code is 401.9.

Next, let’s review the coding guidelines in relation to hypertension.

Coding Guidelines
In the cases where the physician documents either elevated high blood pressure or transient hypertension, assign the code 796.2, elevated blood pressure reading without diagnosis of hypertension.

Coding secondary hypertension requires two codes. The first code identifies the underlying etiology, and the second code (from category 405) identifies the type of hypertension. Sequencing of these codes is dependent on the reason for the admission or encounter.

Two codes are required when coding hypertensive cerebrovascular disease. The first code (from categories 430-438) identifies the type of cerebrovascular disease, and the second code represents the appropriate hypertension code (from categories 401-405).

Coding hypertension and heart disease requires the physician to document a cause-and-effect relationship between the hypertension and the heart disease (e.g., due to hypertension, hypertensive). When the physician documents heart disease due to hypertension, use a code from category 402. For patients who have heart failure, use an additional code from category 428 to identify the type(s) of heart failure. Should the patient have systolic or diastolic heart failure and congestive heart failure, a coder may use more than one code from category 428.


Practical Skill Building for the ICD-10 Coder

Use this series of quizzes to test your knowledge and abilities in ICD-10.

Unlike hypertension and heart disease, when a patient has hypertension and chronic renal disease, the physician does not have to indicate the cause-and-effect relationship between the two. If the documentation supports a patient has both hypertension and chronic renal disease, assign a code from category 403. The fifth digit for category 403 represents the stage of the renal disease. The fifth digit “0” represents with chronic kidney disease (CKD) stage I through stage IV, or unspecified, and the fifth digit of “1” represents with chronic kidney disease stage V or end stage renal disease. Add an additional code from category 585 to represent the chronic kidney disease.

A patient that has both hypertensive kidney disease and hypertensive heart disease documented, assign a code from category 404. A cause-and-effect relationship is still assumed between the hypertension and the CKD even if not designated. Fifth digits for category 404 indicate if the patient has heart failure and the stage of chronic renal disease. The fifth digit of “0” represents without heart failure and with CKD stage I through stage IV, or unspecified. The fifth digit “1” represents with heart failure and with CKD stage I through stage IV, or unspecified. Fifth digit “2” is without heart failure and with CKD stage V or end stage renal disease, and fifth digit “3” is with heart failure and with CKD stage V or end stage renal disease. An additional code for category 428 and 585 should be added as additional codes to represent the type of heart failure and the stage of chronic renal disease.

Taking the CCS can be a stressful experience, but the better prepared a person is going into the exam, the more likely he/she will succeed. While studying for hypertension, go through and study the coding guidelines, and ensure you understand how to use the hypertension table. Having a solid understanding of how to code hypertension cannot only help you succeed on the CCS exam, but also in your coding career.

This month’s column has been prepared by ICD-10-CM/PCS AHIMA Certified Trainer Meredith McCollum, a coding educator with Precyse (www.precyse.com), which provides services and technologies that capture, organize, secure and analyze healthcare data and transform it into actionable information, supporting the delivery of quality patient care and optimizing operating performance. McCollum’s position is dedicated to providing ICD-9 and ICD-10 education to both internal colleagues, as well as clients based across the U.S. She also is an adjunct professor for DeVry University where she not only teaches ICD-9 and ICD-10, but also develops classes for their nationwide Health Information Technology Program.

Take the quiz and test your knowledge on page 2.


1. A 56-year-old male is admitted to the hospital with acute systolic congestive heart failure due to his hypertension. The patient also has a known history of ESRD, which is currently maintained by dialysis, but he does not receive dialysis while in the hospital. How would this encounter be coded?

2. A 45-year-old female presents to the doctor’s office noting a history of headaches for the past month. Her blood pressure is checked and is noted to be slightly elevated at 135/90. The physician wants the patient to monitor her blood pressure at home for the next couple of weeks and follow up. Diagnoses: high blood pressure, headaches.

3. An 85-year-old male presents to the emergency room after the nursing home nurses found him unresponsive. The patient has a previous history of hypertension. A CT scan was performed and the radiologist reported an intracerebral hemorrhage. The patient became more responsive throughout the stay, but continued to struggle with dysphagia. Discharge diagnoses: intracerebral hemorrhage due to hypertension, dysphagia.


1. 404.93 Hypertensive heart and chronic kidney disease stage V or end stage renal disease, with heart failure, unspecified benign or malignant

585.6 End stage renal disease

V45.11 Postprocedural renal dialysis status

428.21 Systolic heart failure, acute

428.0 Congestive heart failure, unspecified

2. 796.2 Elevated blood pressure reading without diagnosis of hypertension

784.0 Headache (facial pain)

3. 431 Intracerebral hemorrhage

401.9 Hypertension, unspecified

787.20 Dysphagia

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