Understanding why ICD-10-CM notes say 'Use additional code' and when two codes are needed.

Outline in brief

• Hook: codes tell more than a name—they tell the whole story

• What “Use additional code” means in plain terms

• Why two codes may be needed: capturing the full clinical picture

• Real-world examples you’ll actually see

• How to apply this in coding today: a practical quick guide

• Resources and tips to stay sharp

Two codes, a better story: the core idea

Here’s the thing about ICD-10-CM notes that say “Use additional code.” They aren’t just busywork. They’re about painting a complete, accurate picture of a patient’s health. The note signals that coding the primary diagnosis alone leaves out important details that can influence treatment, prognosis, and the care plan. So, the guidance is clear: two codes may be required to tell the full story.

In plain terms, the primary code names the main condition. The additional code flags an associated manifestation, complication, or related condition that matters for care. Think of it like a plot twist that helps clinicians and billers understand what else is going on and why their decisions matter.

When you’ll see this note—and why it matters

You’ll encounter “Use additional code” in those moments when the health story isn’t complete with a single diagnosis alone. Some common scenarios:

• A disease comes with a manifestation that changes management. For example, a stroke may be accompanied by aphasia, making communication and rehab goals part of the clinical picture.

• A condition has a complication or related symptom that needs separate attention. Pneumonia can bring dehydration or electrolyte disturbances into play, affecting fluids, meds, and recovery.

• An illness has a comorbidity that’s relevant to prognosis or treatment decisions. Diabetes with kidney disease, obesity, or cardiovascular risk factors often require more than one code to reflect the overall health status.

The practical takeaway: if the chart mentions a manifestation or complication alongside the primary diagnosis, there’s a strong chance two codes are warranted.

Concrete examples you can relate to

Let’s walk through a couple of real-world, believable scenarios. No guesswork, just a straightforward look at how the logic plays out.

• Example 1: Cerebral event with speech impact

Primary diagnosis: ischemic stroke

Manifestation/related condition: aphasia

Codes you’d use: I63.9 for cerebral infarction, and R47.01 for aphasia.

Why this matters: the aphasia isn’t just a side note. It affects therapy planning, discharge needs, and how care teams communicate with the patient.

• Example 2: Lung infection with dehydration

Primary diagnosis: pneumonia

Manifestation/complication: dehydration

Codes you’d use: J18.9 for pneumonia, and E86.9 for dehydration.

Why this matters: dehydration can influence IV fluids, electrolyte monitoring, and the pace of recovery.

• Example 3: Chronic disease with a new twist

Primary diagnosis: type 2 diabetes mellitus

Manifestation/associated condition: obesity

Codes you’d use: a diabetes code (like E11.xx, depending on the exact manifestation) plus E66.xx for obesity.

Why this matters: the body’s overall metabolic state affects treatment choices, medication dosing, and risk stratification.

Note the pattern: the first code names the primary condition; the second code captures something essential that the first alone does not explain.

A practical approach to applying the rule

If you’re staring at a chart and you see the directive “Use additional code,” use this straightforward checklist to stay on track:

1. Read the clinical details carefully

• Does the documentation mention a symptom, complication, or related condition that clearly affects care?

• Are there phrases like “with,” “associated with,” or “complicated by” that point to a second issue?

2. Distinguish the main problem from the companion issue

• The main problem is what brought the patient to care or what is being treated as the primary focus.

• The companion issue is the manifestation or complication that modifies treatment, prognosis, or outcomes.

3. Look for explicit notes in the chart

• If the chart says “with dehydration,” “complicated by,” or “associated with this condition,” that’s your cue to code the extra element.

• If you’re not sure, check the Official Guidelines for Coding and Reporting. They’re there to help you decide when an additional code is appropriate.

4. Verify with reliable references

• Use the ICD-10-CM Tabular List and Alphabetic List to confirm the exact codes.

• Cross-check with trusted resources such as the ICD-10-CM Official Guidelines, the American Health Information Management Association (AHIMA) materials, or your institution’s coding policy.

5. Keep the patient’s care context in mind

• The extra code should reflect information that affects treatment or prognosis, not just something incidental mentioned in the notes.

• Avoid overcoding by including only clinically relevant manifestations and complications.

A few tips to stay sharp

• Practice with real-world notes. Short, scenario-based drills help you see how the “Use additional code” instruction shows up in everyday cases.

• Build a quick mental checklist: primary condition, associated manifestation, and whether the manifestation changes management.

• Don’t assume. If the chart doesn’t clearly state a manifestation, don’t add a code unless the documentation supports it. When in doubt, query the clinician or review guidelines.

• Use reliable sources. The ICD-10-CM codebook and official guidelines are your north stars, but don’t ignore your institution’s local policies.

Why accuracy here isn’t vanity—it matters

Coded data isn’t just for billing. It’s part of the patient’s health record, and it feeds decisions about care quality, epidemiology, and research. When you code both the primary condition and the related manifestation, you’re helping clinicians understand a patient’s full clinical needs. You’re also improving the clarity of health data for future care, public health surveillance, and resource planning. It’s a team effort, and accuracy up front pays dividends downstream.

Common pitfalls to watch for

• Fingers crossed syndrome: assuming a second code is always needed whenever two conditions appear. Sometimes a single, well-chosen code already covers both, especially if a single ICD-10-CM code includes the manifestation. Always verify.

• Overcoding: adding a second code for every symptom popping up in the notes, when the documentation doesn’t support it or when it’s not clinically significant.

• Missing the manifestation entirely: ignoring an accompanying symptom or complication that affects treatment or prognosis.

Where to turn for a quick, reliable reference

• ICD-10-CM Official Guidelines for Coding and Reporting

• ICD-10-CM Coding Guidelines summaries from AHIMA or AAPC

• The ICD-10-CM codebook (print or digital)

• Your hospital’s coding policies and the coder’s desk reference

If you keep these resources handy, you’ll find the “Use additional code” instruction becomes less mysterious and more of a helpful compass.

A final thought

Coding isn’t just about naming conditions. It’s about telling a patient’s health story with as much precision as possible. The note “Use additional code” is a nudge toward completeness—an invitation to add the piece of the puzzle that completes the picture. When you spot it, you’re not just coding—you’re documenting a richer, more accurate health narrative.

If you’d like, I can walk through a few more realistic scenarios you might see in daily work and show how the two-code rule plays out in each. The goal is simple: keep the coding honest, clear, and useful for everyone who touches the patient’s care.