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Anemia, a clinical finding that arises from many etiologies, is defined by a hemoglobin (Hb) value at least 2 standard deviations below the mean for age and sex (<13 g/dL for men and <12 g/dL for women), although Hb values may vary due to pregnancy, smoking, or altitude. Severe anemia is defined as Hb <8 g/dL in people of all ages and in both sexes, except in children 6-59 months of age and pregnant women. Anemia results in nonspecific tissue hypoxia symptoms (e.g., fatigue, weakness, pallor, dizziness, and fainting). More than one billion individuals are affected by anemia worldwide, and iron deficiency anemia accounts for approximately half of anemia cases. Additional types of anemia include anemia of chronic disease/anemia of inflammation (anemia related to infections, inflammation, obesity, cancer, and other causes), megaloblastic anemia (caused by vitamin B12 and/or folate deficiency), hemoglobinopathies/thalassemias (such as sickle cell anemia and alpha and beta thalassemias), hemolytic anemias and aplastic anemias (related to bone marrow disorders), among others. Because anemia treatment depends on the underlying cause, identifying the correct etiology is essential. Initial anemia evaluation includes a CBC with platelet count and automated differential, a reticulocyte count and percent, along with a corrected reticulocyte count, and in some cases, review of a peripheral blood smear. Certain circumstances may warrant a bone marrow biopsy. ,
Quick Answers for Clinicians
Testing for anemia includes CBC with platelet count and automated differential. A CBC includes red blood cell (RBC) indices that can be used to further classify anemia and may indicate possible diagnoses and additional testing needs. A reticulocyte count is commonly ordered with a CBC to assess bone marrow response to anemia. Peripheral blood smears may be used to rapidly identify specific anemias that result in distinctive cellular morphologies. Additional testing, including serum ferritin and iron and iron binding capacity tests, may be performed to reach a definitive diagnosis. Refer to the Anemia Testing Algorithm for more information.
In general, screening for anemia depends on the needs of the individual. Symptomatic patients should be tested at presentation. The U.S. Preventive Services Task Force finds insufficient evidence to recommend universal screening. The American Academy of Family Physicians, however, recommends universal screening at 12 months of age, and the American College of Obstetricians and Gynecologists recommends that all pregnant individuals be screened.
The reticulocyte count is an important indicator of bone marrow production of new red blood cells (RBCs). However, anemia leads to a decrease in the number of RBCs, and thus a falsely elevated percentage of reticulocytes. A corrected reticulocyte count adjusts for anemia and thereby enables assessment of erythropoiesis and the detection of conditions associated with consumption or destruction of RBCs.
Indications for Testing
Testing for anemia is appropriate when individuals present with symptoms of tissue hypoxia, including fatigue, weakness, pallor, dizziness, fainting, shortness of breath, and irregular heartbeat. , Additional testing is indicated to identify the etiology of anemia when a routine screening test reveals an Hb value at least 2 standard deviations below the mean for age and sex.
Laboratory Testing
Initial Evaluation
Complete Blood Count
The first recommended test in the evaluation of suspected anemia is a CBC, which includes an assessment of hematocrit (Hct), Hb, platelets, red blood cell (RBC) and white blood cell (WBC) counts, and RBC indices. The mean corpuscular volume (MCV) result from the CBC will guide further testing. , ,
| MVC Result | Possible Etiologies | Recommended Follow-Up Testing | Associated ARUP Consult Topics |
|---|---|---|---|
| Low MCV (microcytosis) | Iron deficiency anemia (most common) Some hemoglobinopathy traits Anemia of chronic disease/anemia of inflammation Sideroblastic anemia | Iron parameters, HPLC evaluation for thalassemia | |
| Normal MCV (normocytosis) | Anemia of chronic disease/anemia of inflammation (most common) Acute blood loss Hemolysis Renal insufficiency Bone marrow infiltration (leukemia/lymphoma, metastatic disease, granulomatous disease) Aplastic anemia/pure red cell aplasia Multiple myeloma | Corrected reticulocyte count | |
| High MCV (macrocytosis) | Folate and/or vitamin B12 deficiency Certain medications Alcohol abuse (very common) Thyroid disease Liver disease Hemolytic anemias leading to significant reticulocytosis Aplastic anemia | Corrected reticulocyte count, vitamin B12 and folic acid levels | Megaloblastic Anemia |
HPLC, high-performance liquid chromatography | |||
Reticulocyte Count
A reticulocyte count, corrected for anemia (corrected reticulocyte count), is an indicator of bone marrow production of new RBCs and should be ordered in cases of normal or high MCV. The corrected reticulocyte count is elevated in several disease states, including conditions with consumption or destruction of RBCs such as hemolytic anemias, and is normal or decreased in conditions such as megaloblastic and aplastic anemias. , , If there is evidence of bone marrow dysfunction, a peripheral smear should be ordered.
Peripheral Smear
A peripheral smear is used to evaluate cellular morphology, which may suggest a specific etiology for observed anemia. An abnormal smear should always be investigated based on smear characteristics, regardless of any cellular indices. Bone marrow biopsy may be necessary.
| RBC Morphology | Possible Etiology | Associated ARUP Consult Topics |
|---|---|---|
| Spherocytes | Immune hemolytic anemia or hereditary spherocytosis | Hemolytic Anemias |
| Schistocytes/fragmented RBCs | TTP, HUS, DIC | Hemolytic Anemias |
| Bite cells | G6PD deficiency | Hemolytic Anemias |
| Target cells | Hemoglobinopathies, liver disease | Hemolytic Anemias |
| Acanthocytes | Liver disease | — |
| Unusual RBC inclusions | Parasitic inclusions | |
DIC, disseminated intravascular coagulation; G6PD, glucose-6-phosphate dehydrogenase; HUS, hemolytic uremic syndrome; TTP, thrombotic thrombocytopenic purpura | ||
Indications for Bone Marrow Biopsy
Although not generally recommended, bone marrow biopsy may be appropriate when initial laboratory testing is inadequate to reach a diagnosis or when clinical suspicion of iron deficiency persists, regardless of laboratory test results. Bone marrow biopsy may also be required when abnormalities in blood counts and/or a peripheral blood smear are observed.
ARUP Laboratory Tests
Quantitative Spectrophotometry
Quantitative Chemiluminescent Immunoassay
Quantitative Chemiluminescent Immunoassay (CLIA)
References
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WHO - Guideline on Haemoglobin cutoffs-anemia
World Health Organization. Guideline on haemoglobin cutoffs to define anaemia in individuals and populations. Published 2024; accessed Jul 2026.
-
41252836
Latimer K, Baci G, Layne M. Iron deficiency anemia: evaluation and management. Am Fam Physician. 2025;112(5):538-545.
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StatPearls - Anemia Screening
Freeman AM, Zubair M. Anemia screening. In: StatPearls, StatPearls Publishing. Updated Feb 2025; accessed Mar 2026.
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StatPearls - Anemia
Regalla DKR, Killeen RB. Anemia. StatPearls. StatPearls Publishing. Updated Jul 2026; accessed Jul 2026.