The Basics of the ICD-10 Structure

With changes to the ICD-10 code scheduled to go into effect on October 1, 2015, it is important to understand the ICD-10 code sets that are scheduled to replace it. ICD-10 is divided into two general categories for the purposes of reporting medical diagnoses and inpatient procedures. ICD-10-CM covers coding for diagnostics across all healthcare service providers in the United States. ICD-10-PCS is applicable to inpatient hospital procedures in the United States. ML Medical Billing is prepared to tackle on the changes in the coding structure.

ICD-10-CM Code Structure

Pricing & Fees Medical Billing ExpertsThere are several things to keep in mind when becoming familiar with the ICD-10 coding structure. ICD-10 diagnosis codes are made up of a 3-7 character structure, depending on the type and location of the condition.

Three character codes serve as headings in the ICD-10-CM grouping for specific categories. In cases where a diagnostic category can be further subdivided into several branch categories, the 4th, 5th, and 6th characters are added to the code for further differentiation. The second set of characters are used to denote more detail about the diagnosis, including severity, etiology, and anatomical location. The 7th character is optional and typically reserved for instances where more granular specifications are needed, such as in cases of certain injuries or fractures.

It is important to note that codes that do not use all of the required characters are invalid. Certain diagnostic codes allow for a placeholder “X” in cases where a need for further expansion of the code may arise.

External Cause Code Reporting

External cause codes are not required under ICD-10-CM if they were not previously reported under ICD-10-CM, unless mandated by a new State or payer-based requirement.


To make viewing a specific conversion accessible to you, the ML Medical Billing website has an ICD-10 to ICD-10 converter. The tool is a convenient way to get a glimpse of what to expect once the transition is finalized on October 1.

To use the ICD-10 Code Conversion, type in the medical code and select the form of code you are converting from and want to convert to.

If you have any questions about converting from ICD-10 to ICD-10, contact the account executives at ML Medical Billing, they have all of the answers for you. They are ready and anticipating the transition which will take place in a few months.