Which description best captures the ICD code structure?

• A. Exactly 3-7 characters, with 3 before the decimal and up to 4 after
• B. 5-digit numeric codes with no decimals
• C. 3-7 characters with 3 before the decimal and up to 4 after the decimal; First character is alpha; Second character numeric
• D. Codes have 2 digits only

Answer: (C)

ICD codes use an alphanumeric format where the initial portion defines the category and the extension after the decimal adds detail. The first character must be a letter, the second a digit, and the three-character base is placed before the decimal. After the decimal, up to four more characters can follow, allowing the total length to range from 3 to 7 characters. This structure means the code starts with a letter, then a digit, and has three characters before the decimal, with the option for up to four additional alphanumeric characters afterward.

That description fits perfectly: three characters before the decimal and up to four after, with the first character being a letter and the second a digit. It reflects how ICD codes encode category and subcategory detail. The other options describe formats that either rely on only digits, omit the decimal structure, or specify too few characters, which isn’t how ICD codes are organized.