Anemia: Clinical Approach Algorithm | Flowchart Diagram

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Anemia is defined as reduction in number of red blood cells or hemoglobin, resulting in lower oxygen carrying capacity. WHO definition for Anemia is- Hemoglobin less than 13gm/dL for Men and less than 12gm/dL for Women.This post will help you approach anemia algorithm using a flowchart.

The diagnosis of Anemia depends on lab investigations and a brief approach to Anemia. Most fail to approach anemia since the textbook defines anemia in terms of classifications and per categories. In this article, we will try to define exactly how to approach Anemia in a specific pattern using a simple diagram.

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The first aim is to establish whether the anemia is Microcytic, Normocytic or Macrocytic. Upon identification, we reach the specific diagnosis of anemia. Here’s the flowchart to clinical approach to Anemia, however, if you need deep insights, follow our article below.

Anemia Clinical Approach Algorithm Flowchart Diagram
Anemia Algorithm using Flowchart Diagram: Click to zoom

Approach to Anemia: Overview

Evaluation of Anemia requires brief history and physical examination. You can also read our post on anemia concepts including diagnosis, complications and treatment. Following are some clues to understanding anemia algorithm:


Clinical history may reveal most of the clues to diagnosis. One must ask the following questions to achieve maximum outcome:

  1. Nutritional History
  2. Family History
  3. Geographical background
  4. Pregnancy
  5. Alcohol and Tobacco intake
  6. Association of other symptoms- lymphadenopathy, splenomegaly, petechiae, etc.
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Physical Examination

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Of course you have checked for pallor under lower palpebral conjunctiva. But following are signs you must also check for:

  1. Forceful heartbeat
  2. Strong peripheral pulses
  3. Systolic flow murmur
  4. Pale skin
  5. Lighter palmar creases

Laboratory Tests

Once you have got the clue, you may proceed to laboratory investigation for diagnosis of anemia. Following is the list of tests you may want to get done before proceeding to anemia algorithm:

  1. Complete Blood Count (CBC)
  2. Peripheral Blood Smear
  3. Bone Marrow Examination
  4. Iron Supply Studies

1. Complete Blood Count

Complete blood count or CBC will involve the following:

A. Red blood cell count (RBC)

  • Hemoglobin
  • Hematocrit
  • Reticulocyte count

B. Red blood cell indices

  • Mean cell volume (MCV)
  • Mean cell hemoglobin (MCH)
  • Mean cell hemoglobin concentration (MCHC)
  • Red cell distribution width (RDW)

C. White blood cell count

  • Cell differential
  • Nuclear segmentation of neutrophils

D. Platelet count

E. Cell morphology

  • Cell size
  • Hemoglobin content
  • Anisocytosis
  • Poikilocytosis
  • Polychromasia

2. Iron supply studies

  • Serum iron
  • Total iron-binding capacity
  • Serum ferritin

3. Marrow examination

A. Aspirate

  • M/E ratio
  • Cell morphology
  • Iron stain

B. Biopsy

  • Cellularity
  • Morphology

Approaching Anemia Algorithm with CBC and Peripheral Blood Smear

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Once the Complete blood count and peripheral blood smear test results in blood tests are up, you can follow the approach for anemia as given in this chart:

Anemia Clinical Approach Algorithm Flowchart Diagram

Mean Corpuscular Volume (MCV)

MCV is defined as the average volume of red blood cells. It is calculated as:

Mean cell volume (MCV) = (hematocrit x 1O)/(red cell count x 106)

The three conditions can come up with MCV:

  1. MCV less than 80
  2. MCV in between 80-100
  3. MCV above 100
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Implication for each value of Mean Corpuscular Volume:

  1. MCV<80: Microcytic anemia- Small red blood cells
  2. MCV 80-100: Normocytic anemia- Normal sized red blood cells
  3. MCV>80: Macrocytic anemia- Larger red blood cells than normal

For reference: Normal erythrocyte (RBC) volume in humans is 80 to 100 femtoliters (fL= 1015 L).

Approach to Microcytic Anemia

Serum iron studies may reveal low iron and ferritin. However, TIBC (Total Iron Binding Capacity) differentiates between Iron deficiency anemia and Anemia of chronic disease. On the other hand, Mentzer Index is calculated to find if it is Thalassemia.

Low Iron and Ferritin with High TIBC: Iron Deficiency Anemia

Low Iron and Ferrtin with Low TIBC: Anemia of Chronic Disease

Mentzer Index

Mentzer Index = Mean corpuscular volume per red cell count

Mentzer Index = MCV/RBC

Mentzer index of less than 13 suggests thalassemia trait, and an index of more than 13 suggests that the patient has iron deficiency or Anemia of Chronic Disease.

Approach to Normocytic Anemia

Reticulocyte count helps differentiate the normocytic anemia into Hyper-proliferative and Hypo-proliferative.

Reticulocytes are immature red blood cells produced by Bone marrow. Reticulocyte actually predicts how fast red blood cells called reticulocytes are made by the bone marrow and released into the blood.

Normal range of Reticulocyte count: 0.5-1.5%

Hypo-proliferative: <2% Reticulocyte count

Seen in:

  • Leukemia
  • Aplastic anemia
  • Pure red cell aplasia
Hyper-proliferative: >2% Reticulocyte count

Seen in:

  • Hemorrhage
  • Hemolytic anemia

Approach to Macrocytic Anemia

Megalocytes are large non-nucleated red cells. Basically the normal red cells become large in size but same hemoglobin concentration. The presence of these megalocytes means Megaloblastic Anemia.

Megaloblastic Anemia

  • Vitamin B12 deficiency
  • Folate deficiency
  • Drug Induced
  • Non-Megaloblastic Anemia
  • Alcohol abuse
  • Myelodysplastic syndrome
  • Liver disease
  • Congenital bone marrow failure syndromes
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