Anemia is a hematologic condition defined by a reduction in the number of circulating red blood cells (RBCs), the concentration of hemoglobin (Hgb), or the hematocrit (Hct) below established reference thresholds — generally Hgb <13.5 g/dL in adult males, <12.0 g/dL in adult females, and <11.0 g/dL in pregnant women — resulting in impaired oxygen delivery to tissues and organs. Unlike polycythemia, which involves excess RBC production, anemia represents a deficit of oxygen-carrying capacity; it should also be distinguished from leukopenia (low white cells) and thrombocytopenia (low platelets), though all three may coexist in bone marrow failure states such as aplastic anemia (D61.9). The underlying pathophysiologic mechanism falls into one of three broad categories: (1) decreased RBC production (e.g., iron deficiency D50.9, B12/folate deficiency D51.9, D52.9, aplasiaD61.9); (2) increased RBC destruction — hemolysis (e.g., sickle cell D57.1, autoimmune hemolytic anemia D59.10); or (3) blood loss, either acute (D62) or chronic (D50.0). Physiological anemia of pregnancy (D64.89) is a dilutional, non-pathological form; pathological anemias span hereditary and acquired etiologies with severity ranging from mild and asymptomatic to life-threatening. The most clinically relevant subtypes for coding include: iron deficiency (D50.0-D50.9), nutritional deficiency (B12 D51.0-D51.9, folate D52.0-D52.9), hemolytic and hereditary forms (D55.0-D58.9), sickle cell disorders (D57.1-D57.819), aplastic anemias (D60.0-D61.9), acute posthemorrhagic anemia (D62), anemia in chronic disease (D63.0-D63.8), and other/unspecified (D64.0-D64.9). Anemia is commonly confused with pancytopenia — a key distinction: anemia is isolated to the RBC/Hgb line, while pancytopenia involves simultaneous deficiency of all three cell lines (RBCs, WBCs, and platelets) and typically suggests a more serious marrow or systemic disorder.
Noun-forming suffix — “condition of,” “state of,” “abnormal process involving”
The word entered English in the 1820s as anemia (noun), borrowed from French anémie (1761), from the Latinized form of Greek ἀναιμία (anaimía) — “lack of blood” — from ἄναιμος (ánaimos), “bloodless,” literally “without blood.” The British spelling anaemia persisted in clinical literature through the 19th century and remains the standard outside the U.S. The root haima (“blood”) connects anemia to the entire -haem / -hem root family: hematology (haima + logos → study of blood), hemoglobin (haima + Latin globus → blood protein), hemoptysis (haima + ptysis → spitting blood), and hemorrhage (haima + rhegnynai → bursting of blood). The alpha privativean- is among the most productive prefixes in medical terminology, appearing in aphasia, anoxia, apnea, asystole, and agranulocytosis.
🔀 ALIASES / ALTERNATE TERMS
Anemic / Anaemic(adjective form — seen in clinical collocations: “anemic patient,” “anemic murmur,” “anemic pallor”; also used figuratively outside medicine)
Anaemia(British/Commonwealth spelling; used interchangeably with “anemia” in international coding literature and WHO documentation)
Iron deficiency anemia (IDA)(most common type worldwide; caused by inadequate iron intake, absorption failure, or chronic blood loss; coded D50.9 unspecified, D50.0 when due to chronic blood loss)
Megaloblastic anemia(RBCs are abnormally large due to impaired DNA synthesis; most common causes are B12 D51.9 and folate deficiency D52.9; coded to the underlying deficiency)
Hemolytic anemia(premature RBC destruction faster than bone marrow can compensate; may be hereditary D55.x-D58.x or acquired D59.x)
Aplastic anemia(bone marrow failure with pancytopenia; acquired D61.9 or constitutional D61.01; often requires marrow biopsy for diagnosis)
Sickle cell anemia(hereditary hemoglobinopathy — abnormal HbS polymerization → rigid, sickle-shaped RBCs → vaso-occlusion and hemolysis; coded under D57.x family; note: D57.1 is sickle cell disease without crisis)
Anemia of chronic disease (ACD) / Anemia of inflammation(normocytic/normochromic anemia associated with chronic inflammatory, infectious, or neoplastic conditions; coded D63.0 in neoplastic disease, D63.1 in CKD, D63.8 in other chronic diseases)
Thalassemia(hereditary defect in globin chain synthesis → ineffective erythropoiesis + hemolysis; alpha D56.0 and beta D56.1 are most clinically significant; coded under D56.x)
Acute posthemorrhagic anemia(sudden RBC loss from acute bleeding — trauma, GI bleed, surgical hemorrhage; coded D62; note: anemia due to chronic blood loss codes to D50.0, not D62)
Sideroblastic anemia(impaired heme synthesis → iron deposits in mitochondria of erythroblasts; hereditary D64.0 or acquired D64.1, D64.2, D64.3)
🔗 RELATED TERMS
Polycythemia — the opposite of anemia; an abnormal increase in circulating RBC mass; may be primary (polycythemia vera — neoplastic, JAK2 mutation) or secondary (response to hypoxia or elevated EPO); coded D45 (polycythemia vera) or D75.1 (secondary polycythemia)
Pancytopenia — simultaneous deficiency of all three cell lines (RBCs, WBCs, platelets); shares the aplastic anemia mechanism but involves broader marrow failure; coded D61.818 or D61.9 depending on etiology
Hemoglobin — the iron-containing protein within RBCs responsible for oxygen transport; the primary measurable marker of anemia severity; forms the basis of WHO Hgb thresholds used in coding and clinical decision-making
Hematocrit — the percentage of blood volume occupied by RBCs; used alongside Hgb to classify anemia severity and monitor treatment response; not separately coded but drives clinical documentation
Erythropoietin (EPO) — glycoprotein hormone produced by the kidneys that stimulates RBC production in bone marrow; exogenous ESA (erythropoiesis-stimulating agent) therapy is used in anemia of CKD (D63.1) and cancer-related anemia (D63.0)
Hemolysis — premature destruction of RBCs; the core mechanism of hemolytic anemias (D55-D59); may be intravascular or extravascular; triggers release of LDH, indirect bilirubin, and free hemoglobin
Reticulocyte — immature RBC; reticulocyte count is a key lab value in classifying anemia as hypoproliferative (low retic → bone marrow problem) vs. hyperproliferative (high retic → hemolysis or blood loss)
Ferritin — primary iron storage protein; low serum ferritin is the most sensitive early marker of iron deficiency; paired with TIBC and serum iron to differentiate IDA from ACD
Intrinsic factor — glycoprotein secreted by gastric parietal cells required for B12 absorption in the ileum; absence due to autoimmune gastritis causes pernicious anemia (D51.0)
Splenomegaly — enlarged spleen common in hemolytic anemias; the spleen sequesters and destroys abnormal or antibody-coated RBCs; coded separately (D73.1 or R16.1 depending on context)
Bone marrow failure — underlying mechanism of aplastic anemia; may be autoimmune, drug-induced, or idiopathic; documented failure requires marrow biopsy
Transfusion reaction — adverse response to blood product administration; must be coded separately using T80.xx codes when it occurs; triggers additional documentation and workup
CODING CORNER
🏥 ICD-10-CM CODES
Iron Deficiency Anemia (D50.x)
Code
Description
D50.0
Iron deficiency anemia secondary to blood loss (chronic)
Level IV surgical pathology, gross and microscopic examination (bone marrow biopsy interpretation — always reported separately from 38221/38222)
⚠️ Coding Note: The D63.x category (anemia in chronic disease) follows a mandatory code-first sequencing rule — the underlying condition (e.g., the neoplasm for D63.0, the specific CKD stage for D63.1) must be sequenced as the principal/first-listed diagnosis, with D63.0-D63.8 as an additional/secondary code; failure to follow this sequencing is a common audit finding on inpatient profee claims. For D64.81 (anemia due to antineoplastic chemotherapy), code the malignancy first, then D64.81, then the adverse effect of the antineoplastic agent from T45.1X5A/D/S — all three codes are typically required for complete capture. A high-yield undercoding alert: when documentation states “anemia” without further specification, coders default to D64.9, but a query is warranted when labs show microcytic/hypochromic indices (suggesting D50.9) or macrocytic indices (suggesting D51.9 or D52.9) — specificity impacts MS-DRG assignment and clinical quality metrics. For sickle cell disorders, crisis status and crisis type are required for the highest specificity codes (D57.01 acute chest syndrome vs. D57.02 splenic sequestration vs. D57.09 other) — “in crisis” without documentation of crisis type defaults to the unspecified crisis codes (D57.00); query the attending when crisis type is clinically evident from nursing notes but not explicitly stated by the provider. Note that D57.3 (sickle cell trait) represents a carrier state and is not a disease — it should never be coded as the reason for admission or sequenced as principal diagnosis.
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