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Ch. 10

Course 10: ICD-9-CM and ICD-10-CM Codes

The International Classification of Diseases (ICD) code is one of the most essential pieces of the medical billing and coding process. Created by the World Health Organization (WHO) as a way of standardizing healthcare classification, ICD codes are diagnostic codes that represent all aspects of a medical diagnosis, including symptoms, social circumstances, cause of injury or disease, and more.

Exploring the ICD-9 and ICD-10 with Easy Lookup Tools
On this page are two tools for investigating ICD-9-CM and ICD-10-CM codes. They are a good place to get started with your education in medical billing and coding.

ICD-9-CM Tool

To use the ICD-9-CM tool, simply type the name of a disease or injury in the search field. The search engine should then give you the corresponding ICD-9-CM code. You can look up that code in the ICD-9-CM index, available through the CDC. You will have to download a copy and open it as an RTF file.

ICD-10-CM Tool

Use the ICD-10 -CM Tool to search by the name of the disease or injury, or by the code itself. You can then take your search results and use them to find more information on the World Health Organization’s version of ICD-10-CM. Click on the chapter title (like “diseases of the respiratory system”) in the drop-down menu on the left to get a list of code blocks that chapter contains. You can also click the arrow button to the left of the chapter title to navigate the drop-down menu from the sidebar.

Background on the ICD

ICD-9—the ninth revision of the International Classification of Diseases—was published in 1978 by the WHO and adapted for use in America by the NCHS. ICD codes were originally intended to be used for epidemiological purposes, but in the United States these codes are used by healthcare providers and insurance companies for billing and reimbursement.

In America, “CM” stands for “Clinical Modification,” which was instituted in the United States by the National Center for Health Statistics (NCHS) to provide additional information related to diagnosis and procedural codes. The CM allows for a much wider spectrum of specific information. ICD-9-CM is updated annually on October 1st in order to reflect new diagnoses, practices, and procedures in the healthcare industry.

How the ICD-9-CM Works

ICD codes create a standard vocabulary for identifying causes of illness, injury, and death around the world.

Physical copies of the ICD-9-CM codes are divided into volumes. Volume 1 contains a tabular list of codes (codes listed by number with the diagnosis following the number) and Volume 2 contains an alphabetical list of symptoms and diagnoses. The third volume for each of these contains procedure codes, which are only used by hospitals to report surgeries performed in their facility. Healthcare providers and insurance companies only use the first two volumes. For the purposes of this course, you will be looking up ICD codes entirely online, but it is still helpful to understand the organization of the ICD manuals.

The 5-digit numeric ICD-9-CM codes are organized from 000 to 999 according to the type of disease or injury they describe. For instance, codes in the 320-359 range represent diseases of the nervous system, such as encephalitis or meningitis. Codes 800-999 correspond to injury and poisoning, like dislocation (codes 830-839) or poisoning by drugs, medications, or other biological substances (codes 960-979).

Those first three digits in an ICD-9-CM code describe the general type of injury or disease, and are called the “category.” The category can be followed by a decimal point and up to two other digits, which provide more specific information about the type, location, and severity of the disease or injury. These last two digits are called the subcategory, and allow coders to increase the level of specificity of their report on a disease or injury.


The code 722.52 corresponds to degenerative disc disease of the lumbar, where:

  • The 3-digit code, or category, “722” corresponds to “intervertebral disc disorders” in the list of diseases and injuries
    • The two-digit sub-subcategories refers to degenerative disc disease, lumbar

Generally speaking, the more digits in a code, the more specific the type, cause, and/or area of injury or disease.

There are also two sets of alphanumeric codes in ICD-9-CM. E-codes describe external causes of injury, while V-codes describe factors that influence health status and/or describe interactions with health services. An example of an e-code would be E905.2, which describes a scorpion sting causing poisoning and toxic reactions. An example of a V-code is V30.00, which describes a single live infant (V30) born in a hospital (V30.0) without mention of caesarean section (V30.00). Like the numeric codes in ICD-9-CM, each of these codes has varying degrees of specificity based on the incident.

Preparing for the Change to ICD-10

The ICD-9-CM will be replaced by the updated ICD-10 in late 2014. In order to comply with this change, healthcare providers, insurance companies, and clearinghouses must all be prepared to fully adopt ICD-10-CM by October 1, 2014. All claims filed with ICD-9-CM after that date will be rejected as non-compliant. Procedures arranged or completed before that date may still be filed with ICD-9-CM.

This switch is happening for a variety of reasons. For one, the ICD-9-CM is out of room. ICD-9-CM is set up so every category can only have 10 subcategories. As it currently stands, the ICD-9-CM can only classify around 13,600 diagnoses, compared to ICD-10-CM’s estimate of 69,000. As diagnoses continue to expand, the system can no longer support the breadth of medical study. The ICD-10 is also better suited for modern technological advances in the field, allowing for more optimized analysis of disease patterns and treatment outcomes.

There are similarities between the two code sets. The conventions and guidelines for assignment codes are largely the same, as is the organization of both sets. For instance, the first chapter, or category cluster, in both ICD-9-CM and ICD-10 is “Certain infectious and parasitic diseases,” so any professional qualified to manage ICD-9-CM should not have a problem with ICD-10. However, there are also key differences between the ICD-9-CM and ICD-10 systems, requiring a conversion on the part of the medical coder.

The composition of codes in the ICD-9-CM is primarily numeric, with limited alphanumeric additions, as discussed above. Valid ICD-9-CM codes are three, four, or five digits. In ICD-10-CM, all codes are alphanumeric and may be anywhere from three to seven digits, depending on the need for specificity. For instance, in ICD-9-CM, the cluster for “Certain infectious and parasitic diseases” is 001-139. In ICD-10 that same cluster would be labeled A00-B99.

Here is a broader example of the tabular breakdowns in ICD-9-CM and ICD-10:


  • Certain infectious and parasitic diseases (001-139)
    • Intestinal infectious diseases (001-009)
      • Cholera (001)
        • Cholera due to vibrio cholerae (001.0)
        • Cholera due to vibrio cholerae eltor (001.1)
        • Unspecified (001.9)


  • Certain infectious and parasitic diseases (A00-B99)
    • Bacterial infections, other intestinal infectious diseases, and STDs (A00-A79)
      • Intestinal infectious diseases (A00-A09)
        • Cholera (A00)
          • Cholera due to vibrio cholerae (A00.0)
          • Cholera due to vibrio cholerae eltor (A00.1)
          • Unspecified (A00.9)

As you can see, the two code sets are largely similar, but with key differences. The alphanumeric numbering system of ICD-10 follows the same tabular tree as the numeric system in ICD-9-CM, adding a new subcategory within the A00-A79 cluster. As medical coders prepare for the shift, plenty of resources will be made available to translate ICD-9-CM into ICD-10.

Because ICD-10 and ICD-10-CM have a significantly larger set of codes than ICD-9 and ICD-9-CM, direct translation between the two code sets is impossible. The translation of ICD-9-CM codes into ICD-10-CM codes using a “crosswalk” program will be discussed in Course 11.

Watch for Coding Notes

In many cases, codes will have notes attached to them that prevent redundancies or inaccurate coding. These notes help medical coders accurately translate the diagnosis into code, and may include instructions like:

  • “Code first,” in which case the coder must list an underlying condition or prior procedure
  • “Includes,” which tells the coder which symptoms or afflictions the code contains
  • “Excludes” or “excludes1,” which are especially important. Unique to ICD-9-CM, the “excludes” note instructs the coder that there is another, more appropriate code for a certain diagnosis. “Excludes1” indicates that the term listed under the “excludes1” field cannot occur simultaneously with the term listed above it. For example, systemic inflammatory response syndrome (SIRS) is coded as R65.1, but excludes severe sepsis (R65.2).

Those these notes can be complicated, they are essential for coding accurately. Even the smallest mistake can cause a medical claim to be denied, creating more work for the office and possibly delaying vital payments from the insurance company to a patient.

Wrapping Up Course 10

Switching to the ICD-10 may seem intimidating, but you can get a jump start on preparing yourself for the changes in the industry using the tools featured on this page. Combined with an understanding of how the new version of the ICD is structured, they will help you make a smooth transition into using the new system.

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