Code First vs. Use Additional Code vs. Code Also: Understanding Three ICD-10-CM Instructional Notes Every Medical Coder Should Know

By Linda Tauber, CPC, CPMA, CRC, CPB

AAPC Approved Instructor

Linda’s Coding Corner | Certify Me Now Medical Coding

If you’ve ever found yourself wondering whether to code the underlying condition
first, add another diagnosis code, or change the sequencing entirely, you’re not
alone.

One of the most common mistakes made by both new and experienced medical coders
is overlooking the instructional notes found throughout the ICD-10-CM Tabular List.
These notes are just as important as the diagnosis codes themselves and can
significantly impact coding accuracy, reimbursement, and compliance.

Three of the most frequently misunderstood instructional notes are
Code First, Use Additional Code, and
Code Also. Although they may appear similar, each serves a
different purpose and must be applied correctly.

Let’s break them down.

A Code First note instructs the coder to sequence the
underlying etiology (cause) before assigning the code for the manifestation
or condition being treated.

Many conditions cannot occur independently and are the result of another
disease process. The ICD-10-CM classification requires the underlying
condition to be reported first because it explains why the manifestation exists.

• Diabetic complications
• Hypertensive chronic kidney disease
• Parkinson disease with associated conditions
• Certain neurologic manifestations

A Use Additional Code note tells the coder that more
information should be reported when documentation supports it.

Unlike a Code First note, this instruction doesn’t necessarily identify an
underlying disease. Instead, it tells you to add another diagnosis code that
provides greater clinical specificity.

• Disease severity
• Associated conditions
• Infectious organisms
• Tobacco use or exposure
• Disease stage
• External causes when applicable

For example, many chronic conditions instruct the coder to
Use Additional Code to identify the stage of the disease
or other clinically relevant details documented by the provider.

A Code Also note often creates the most confusion.

Unlike Code First, a Code Also note does not automatically establish
sequencing. Instead, it indicates that two conditions may both need
to be reported when supported by the medical record.

• The reason for the visit
• Provider documentation
• Official ICD-10-CM coding guidelines

Ignoring instructional notes can lead to:

• Incorrect code sequencing
• Incomplete diagnosis reporting
• Medical necessity denials
• Claim rejections
• Compliance concerns
• Lost reimbursement opportunities

Many CPC exam questions are designed to test whether you notice the
instructional notes — not just whether you can locate the
diagnosis code.

These notes frequently determine the correct answer on the exam.

Whenever you assign an ICD-10-CM diagnosis code:

Developing these habits will improve coding accuracy and help reduce denials
while strengthening your confidence as a coder.

The ICD-10-CM Tabular List is much more than a list of diagnosis codes — it’s
a comprehensive set of coding instructions. Understanding the difference between
Code First, Use Additional Code, and
Code Also is essential for accurate sequencing, complete diagnosis
reporting, and compliance with the Official ICD-10-CM Coding Guidelines.

The next time you’re coding, challenge yourself to read every instructional note
before finalizing your codes. That simple habit can make a significant difference
in your coding accuracy and exam success.