What is the first character of an ICD-10-CM code?

The first character of an ICD-10-CM code is always a letter. This is foundational to the structure of the ICD-10-CM coding system. These codes begin with an alphabetical character that indicates the chapter in the classification system, generally correlating with a specific category of diseases or conditions.

For instance, the codes that start with the letter "A" are related to infectious and parasitic diseases, while codes beginning with "E" pertain to endocrine, nutritional, and metabolic diseases. The use of letters as the initial characters is crucial for the organization and categorization of medical diagnoses, ensuring that codes can be easily understood and utilized for billing and record-keeping.

The other options, while potentially valid in different contexts, do not apply to the structure of ICD-10-CM codes. A number, symbol, or punctuation mark cannot serve as the first character in these specific medical codes. Therefore, the correct answer demonstrates an understanding of the coding system's framework and facilitates accurate coding practices essential for healthcare documentation and reimbursement.