Code the anemia first when chemotherapy causes anemia to reflect the patient’s immediate clinical needs.

Let’s untangle a classic sequencing question that shows up in ICD-10-CM notes more often than you might think: If anemia is caused by chemotherapy, which code should come first?

Short answer: A. Anemia.

But why is that the right move? And how do you think through it in real medical documentation? Let’s break it down in a way that’s practical, not abstract, so you can see the logic at work—not just memorize a rule.

First, the big idea: principal diagnosis vs. the rest

In clinical coding, the principal diagnosis is the condition that, after study, is determined to be chiefly responsible for the patient’s encounter and the need for treatment. In everyday language: what is happening right now that drives the care you’re delivering?

When anemia shows up as a direct consequence of chemotherapy, the anemia is the symptom or complication that the care team is actively diagnosing and treating at that visit. The chemotherapy itself, and the underlying cancer (the neoplasm), are important parts of the medical story, but they don’t take precedence over the current problem that is guiding management.

That might feel a little counterintuitive at first. After all, chemotherapy is the mechanism by which the anemia happened, and the cancer is the root cause of the whole clinical picture. But coding guidelines are built around the idea that the condition requiring the most immediate attention gets top billing. In this case, the patient’s anemia—because of its symptoms, risks, and the direct treatment plan (e.g., transfusion, iron therapy, dose adjustments, or symptomatic support)—is what the chart documents as the principal issue.

So, yes, through the lens of sequencing, anemia comes first. The neoplasm and the chemotherapy-related factors follow as secondary codes that describe the broader context.

Let me explain with a simple mental model

Think of coding like organizing a filing cabinet. The file you open first should be the one that best explains why the patient is there today, what you’re actively treating right now, and what will guide the immediate care plan. The underlying cause—the cancer—and the therapy the patient is receiving live in the neighboring folders. They’re crucial for a complete medical record, but they aren’t the top entry if the patient’s current state is anemia that needs attention now.

If you’ve ever watched a busy ER, you know the same principle plays out in the real world: the patient’s most urgent problem drives the initial diagnosis naming. The background conditions inform the rest of the story, but they don’t automatically take the lead every time.

How to think about the sequencing in a real chart

Here’s a practical approach you can apply to notes that involve anemia from chemotherapy:

• Identify the current issue driving care: If the team documents anemia as the primary problem needing management right now, that’s your principal diagnosis.

• Check the documentation: Is the anemia described as a result of chemotherapy or as a direct complication of the cancer itself? If it’s clearly tied to chemotherapy, that supports anemia as the principal diagnosis.

• Decide what to code next: After the anemia, list codes for the underlying neoplasm and any therapy-related effects that are clinically relevant and documented (for example, chemotherapy as a treatment course, or a coded adverse effect if the record supports it).

• Keep the logic visible in the record: A well-ordered note will show the anemia as the presenting problem, followed by the cancer type, and then the treatment-related details. The coding should mirror that flow so it’s easy for someone else to follow.

A quick, concrete example

Imagine a patient with a known malignancy who develops symptomatic anemia during chemotherapy. The chart notes say: “Chemotherapy-induced anemia requiring red cell transfusion; management includes supportive care; underlying cancer remains active.” In that case:

• First code: the anemia (the condition currently being treated and causing the most attention).

• Second code: the neoplasm (the underlying disease driving the entire clinical course).

• Third code: the chemotherapy or its adverse effects, if the documentation clearly notes them as a contributing factor to the anemia or as part of the treatment record.

This sequencing matches the intent of the guidelines: address the patient’s present complication first, then fill in the “why” and “how” behind it.

A few helpful nuances to keep in mind

• Not all anemia is chemotherapy-induced in every chart, so always verify the cause as documented. If anemia is due to the cancer itself rather than treatment, the sequencing could look different.

• Adverse effects of chemotherapy can appear in the notes, but they don’t automatically outrank the anemia if the anemia is the clinical focus at that encounter.

• The underlying neoplasm isn’t ignored; it should be coded, but typically as a secondary code so the current problem remains the principal focus of the encounter.

Common pitfalls (and how to avoid them)

• Sequencing assumptions: Don’t assume the neoplasm should automatically be the principal diagnosis. If the chart shows the patient’s acute anemia is the reason for the visit and admission, anemia should take precedence.

• Documentation gaps: If the link between chemotherapy and anemia isn’t explicit, you may need to consult the clinician or rely on the best-supported interpretation in the notes. Clear linkage (e.g., “anemia secondary to chemotherapy”) helps.

• Overloading with codes: It’s important to capture the full clinical picture, but avoid clutter. Start with anemia, then layer in the neoplasm and therapy-related elements as supported by documentation.

A few practical tips to keep your coding crisp

• Use the patient’s current presentation as your compass. If the chart reads like “anemia due to chemotherapy,” that’s the compass needle pointing to anemia first.

• Always verify the primary reason for the encounter. If the team’s focus shifts to the cancer or to therapy side effects during the visit, be ready to adjust the principal diagnosis accordingly.

• Document clarity matters. When in doubt, write a precise note about the causal relationships (e.g., “Anemia secondary to chemotherapy for breast cancer”) to guide correct sequencing.

Why this matters beyond a single question

Coding isn’t just about tallying numbers. It shapes patient care, research data quality, reimbursement, and the overall story clinicians share about a patient’s journey. When anemia is the presenting problem, coding it first reflects the patient’s immediate needs and helps the medical team track how that problem is being managed. The underlying cancer and the therapy used to treat it stay in view, but they don’t overshadow the current, pressing issue.

If you’re new to ICD-10-CM sequencing, you’re not alone in finding it a bit like solving a puzzle with missing pieces. The pieces are there in the chart; you just have to figure out which one belongs at the top. Remember, the principal diagnosis is the one that best explains the encounter. In the scenario where anemia stems from chemotherapy, anemia is that top piece.

A quick wrap-up

• Correct answer to the scenario: Anemia should be reported first.

• Why: It’s the condition driving the current care and the reason for the encounter, with the cancer and chemotherapy descriptions following as supportive context.

• How to apply: Check the chart for explicit links between anemia and chemotherapy, sequence anemia first, then code the neoplasm and any related therapy details as secondary codes.

• What to keep in mind: Always align with documentation, ensure the causal relationships are clear, and focus the principal diagnosis on the issue being actively treated.

If this kind of sequencing question pops up in your day-to-day work, you’re in good company. It’s a nimble dance between clinical reality and coding rules, and getting comfortable with it pays off in clearer records, better communication among care teams, and more accurate data for everyone who relies on those codes.

A final nudge: when you’re reviewing notes like this, pause for a moment and picture your patient’s chart as a short, clear story. The first line should tell you what’s happening now. The rest fills in the who, why, and how. That’s the essence of good coding—concise, precise, and human.