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The 6 Major Differences Between ICD-9 and ICD-10 Codes

December 9, 2014


The Department of Health and Human Services (HHS) recently announced that ICD-9 codes will be replaced by the newer ICD-10 codes beginning October 1, 2015. To be ready for the change, your office should begin preparing for the switch right now. To help you do this, we have put together a short list of things that you shouldn’t miss. Here are the 6 major differences between ICD-9 and ICD-10 codes you should know in order to simplify your switch to the new system.

#1. Number of digits used

ICD-10 diagnosis codes may contain more digits than the traditional ICD-9 codes. ICD-9 codes can contain between three and five digits, but ICD-10 codes can be anywhere from three to seven digits long. This is done in order to create codes that are more specific, in addition to accounting for diseases and conditions not covered under ICD-9.

#2. First Digit

ICD-10 codes begin with a letter, while the first digit of an ICD-9 code can be either alpha or numeric. As such, one of the easiest ways to determine if you are using ICD-9 codes is to make sure the first digit is not a number.

#3. Second Digit

There is no change when it comes to the character requirement for the second digit of an ICD-10 code. The second digit of both ICD-9 and ICD-10 codes are always numeric.

#4. Third and subsequent digits

Previously, digits three through five of ICD-9 codes were always numeric. Third and subsequent digits of ICD-10 codes may be either alpha or numeric.

#5. Ability to add new codes

One of the biggest reasons for the change from ICD-9 to ICD-10 is the ability the new system brings when it comes to adding new codes. ICD-10 provides a great deal of flexibility for creating new codes, making it easy to add recently-discovered diseases. The old system contained approximately 17,000 codes, but there are nearly 160,000 included in the new one. Even more codes may be added to ICD-10 as time goes on.

#6. Specificity

ICD-10 codes are also very specific, and are therefore designed to eliminate coding errors that could result in denied claims. Many believe being more specific will also lead to improved patient safety, a more accurate and detailed diagnosis, and fewer requests for documentation to support a diagnosis. It should also lead to fewer claims being denied due to a “lack of medical necessity.”


Switching to ICD-10 will require a number of changes to the way medical billing and coding is done. One of the biggest involves adapting to new insurance payer guidelines, particularly when it comes to Medicare and Medicaid. It’s essential your office is prepared; otherwise, you run the risk of having a large number of claims denied. Outsourcing your billing and coding functions to M-Scribe is one of the best ways to ensure you are in compliance. To find out more about how your business can save a few headaches and a whole lot of money, please feel free to contact us at any time.


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