D50.9
D50 — Iron deficiency anemia
Chapter 3: Diseases of the Blood and Blood-Forming Organs and Certain Disorders Involving the Immune Mechanism (D50-D89)
D50-D53: Nutritional anemias
Clinical Definition
Iron deficiency anemia (IDA) is a condition in which the blood lacks adequate healthy red blood cells due to insufficient iron. Iron is essential for the production of hemoglobin, the protein in red blood cells that carries oxygen throughout the body. When iron stores are depleted, the body cannot produce enough hemoglobin, resulting in smaller-than-normal red blood cells (microcytosis) and reduced oxygen-carrying capacity. Common symptoms include fatigue, weakness, pallor, shortness of breath, dizziness, brittle nails, and pica.
ICD-10-CM code D50.9 is assigned when the diagnosis of iron deficiency anemia is confirmed but the underlying cause or specific type is not further specified in the clinical documentation. This is the most frequently used code within the D50 category and serves as the default code for iron deficiency anemia when the documentation does not indicate whether the anemia is secondary to chronic blood loss, dietary insufficiency, or another identifiable mechanism.
Diagnosis is typically supported by laboratory findings including low serum ferritin (the most specific marker for iron deficiency), low serum iron, elevated total iron-binding capacity (TIBC), low transferrin saturation, and a peripheral blood smear showing microcytic hypochromic red blood cells. A complete blood count (CBC) will characteristically show reduced hemoglobin, reduced hematocrit, low mean corpuscular volume (MCV), and low mean corpuscular hemoglobin (MCH).
When to Use D50.9
- ✓The patient has a confirmed diagnosis of iron deficiency anemia but the documentation does not specify the underlying etiology (e.g., blood loss, dietary deficiency, malabsorption).
- ✓Laboratory findings are consistent with iron deficiency anemia (low ferritin, low serum iron, elevated TIBC, microcytic hypochromic indices) and the provider documents 'iron deficiency anemia' without further qualification.
- ✓The provider documents 'microcytic anemia due to iron deficiency' without specifying a cause such as chronic blood loss or sideropenic dysphagia.
- ✓The patient is being treated empirically with iron supplementation for suspected iron deficiency anemia and the workup for a specific cause is still pending or inconclusive.
- ✓Follow-up encounters for ongoing management of iron deficiency anemia where the original cause was never determined or documented.
Common Coding Mistakes
- ⚠Using D50.9 when the documentation clearly identifies chronic blood loss as the cause. If menorrhagia, GI bleeding, or other chronic blood loss is documented, use D50.0 (iron deficiency anemia secondary to blood loss) instead.
- ⚠Confusing D50.9 with D64.9 (anemia, unspecified). D50.9 should only be used when iron deficiency has been confirmed; D64.9 is appropriate when the type of anemia has not been established.
- ⚠Assigning D50.9 for anemia of chronic disease (ACD). Anemia of chronic disease has a different pathophysiology involving inflammatory cytokine-mediated iron sequestration and should be coded to D63.8 (anemia in other chronic diseases) or the underlying condition, not D50.9.
- ⚠Using D50.9 when more specific documentation is available. Always query the provider when the record suggests a specific etiology, as a more specific D50 code may be warranted.
- ⚠Failing to code the underlying cause alongside D50.9 when one is identified during the encounter. If a GI malignancy or other condition causing the iron deficiency is documented, it should be coded as an additional diagnosis.
Related & Differential Codes
| Code | Description | Relationship |
|---|---|---|
| D50.0 | Iron deficiency anemia secondary to blood loss (chronic) | Sibling |
| D50.1 | Sideropenic dysphagia (Plummer-Vinson syndrome) | Sibling |
| D50.8 | Other iron deficiency anemias | Sibling |
| D63.1 | Anemia in chronic kidney disease | Related |
| D64.9 | Anemia, unspecified | Related |
| D50 | Iron deficiency anemia (category) | Parent |
Documentation Requirements
- 1Confirm the diagnosis of iron deficiency anemia with supporting laboratory values (serum ferritin, serum iron, TIBC, transferrin saturation, CBC with red cell indices).
- 2Document the clinical basis for the diagnosis, including signs and symptoms such as fatigue, pallor, tachycardia, or koilonychia.
- 3Specify whether the iron deficiency anemia is secondary to blood loss, dietary insufficiency, malabsorption, or another identifiable cause. If the cause is unknown, document that the etiology is unspecified.
- 4Record the severity of anemia based on hemoglobin levels (mild: 10-12 g/dL in women or 10-13.5 g/dL in men; moderate: 7-10 g/dL; severe: below 7 g/dL) to support medical necessity for treatment.
- 5Document the treatment plan, including iron supplementation route (oral vs. intravenous), dosage, and expected duration of therapy.
- 6Note any relevant comorbidities or conditions that may contribute to or complicate the iron deficiency anemia, such as chronic kidney disease, inflammatory bowel disease, or celiac disease.
- 7For recurrent encounters, document the response to treatment, follow-up lab results, and any changes to the management plan.
Reimbursement & Billing Notes
D50.9 is a billable and specific ICD-10-CM code that is accepted by all major payers for reimbursement. It is commonly used to justify laboratory monitoring (CBC, iron studies, ferritin), office visits for anemia management, and iron supplementation therapy including both oral and intravenous formulations. Intravenous iron infusion (CPT 96365-96368 for infusion, J1756 for iron sucrose, J1439 for ferric derisomaltose, Q0138 for ferric carboxymaltose) typically requires documentation of oral iron intolerance or failure, along with hemoglobin and ferritin levels, to meet medical necessity criteria.
Payers may request additional documentation or prior authorization for IV iron therapy, particularly for outpatient infusions. When submitting claims, ensure the diagnosis code is supported by laboratory evidence in the medical record. Some payers may downcode or deny claims if the documentation suggests the anemia is better classified under a more specific code (e.g., D50.0 for blood loss-related iron deficiency) or if iron deficiency has not been laboratory-confirmed. Linking D50.9 to the appropriate evaluation and management (E/M) code and any procedure codes ensures proper reimbursement for the level of care provided.
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Try Free — No Credit Card RequiredFrequently Asked Questions
What is the ICD-10 code for microcytic anemia?
The most commonly used ICD-10 code for microcytic anemia due to iron deficiency is D50.9 (Iron deficiency anemia, unspecified). Microcytic anemia is characterized by smaller-than-normal red blood cells (low MCV) and is most frequently caused by iron deficiency. If the microcytic anemia is confirmed to be due to iron deficiency but no specific cause is documented, D50.9 is the appropriate code. If the microcytic anemia is secondary to chronic blood loss, use D50.0 instead. Note that not all microcytic anemias are due to iron deficiency; thalassemia trait (D56.3), sideroblastic anemia (D64.0-D64.3), and lead poisoning (T56.0) can also cause microcytosis and have their own ICD-10 codes.
What is the difference between D50.9 and D50.0?
D50.9 (Iron deficiency anemia, unspecified) is used when the patient has confirmed iron deficiency anemia but the underlying cause is not specified in the documentation. D50.0 (Iron deficiency anemia secondary to blood loss, chronic) is used when the iron deficiency anemia is specifically attributed to chronic blood loss, such as from heavy menstrual periods (menorrhagia), gastrointestinal bleeding (peptic ulcers, colorectal polyps, hemorrhoids), or other sources of ongoing blood loss. The key distinction is whether the documentation identifies chronic blood loss as the etiology. If it does, use D50.0; if the cause is not stated or is unknown, use D50.9.
When should I use D50.9 vs D64.9?
Use D50.9 when iron deficiency has been confirmed as the cause of the anemia, typically supported by laboratory findings such as low serum ferritin, low serum iron, elevated TIBC, and microcytic hypochromic red cell indices. Use D64.9 (Anemia, unspecified) when the patient has anemia but the type or cause has not been determined or documented. D64.9 is a less specific code and should only be used when the workup is incomplete or the provider has not specified the type of anemia. If iron studies confirm iron deficiency, D50.9 is the more accurate and specific code and should be preferred over D64.9.
Can I use D50.9 for anemia of chronic disease?
No. Anemia of chronic disease (ACD), also known as anemia of inflammation, has a fundamentally different pathophysiology from iron deficiency anemia and should not be coded as D50.9. In ACD, iron is sequestered in macrophages due to elevated hepcidin levels driven by inflammatory cytokines, resulting in functional iron deficiency despite adequate or elevated iron stores. Ferritin is typically normal or elevated in ACD, whereas it is low in true iron deficiency. The appropriate code for anemia of chronic disease is D63.8 (Anemia in other chronic diseases classified elsewhere), sequenced after the code for the underlying chronic condition. If a patient has both true iron deficiency anemia and anemia of chronic disease concurrently, both D50.9 and D63.8 may be reported.
What labs support coding D50.9 for iron deficiency anemia?
The key laboratory findings that support a diagnosis of iron deficiency anemia coded as D50.9 include: low serum ferritin (below 30 ng/mL is highly suggestive, below 12 ng/mL is diagnostic), low serum iron, elevated total iron-binding capacity (TIBC), low transferrin saturation (below 20%), and a CBC showing low hemoglobin, low hematocrit, low MCV (microcytosis), and low MCH (hypochromia). A peripheral blood smear may show microcytic hypochromic red blood cells, target cells, and pencil cells. Reticulocyte hemoglobin content (CHr) below 28 pg is another early marker. In ambiguous cases, soluble transferrin receptor (sTfR) levels may be elevated, helping distinguish iron deficiency from anemia of chronic disease where sTfR is typically normal.
Is D50.9 a billable ICD-10 code?
Yes, D50.9 is a valid, billable ICD-10-CM code that is accepted by Medicare, Medicaid, and commercial insurance payers. It is specific enough for claims submission and does not require additional characters. D50.9 can be used as either a primary or secondary diagnosis code depending on the clinical scenario. It supports reimbursement for evaluation and management visits, laboratory testing (CBC, iron studies, ferritin), oral iron supplementation, and intravenous iron infusion therapy when medical necessity is documented.