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Red blood cells, sickle cell
Red blood cells, sickle cell

Red blood cells, tear-drop shape
Red blood cells, tear-drop shape

Red blood cells, normal
Red blood cells, normal

Red blood cells, elliptocytosis
Red blood cells, elliptocytosis

Red blood cells, spherocytosis
Red blood cells, spherocytosis

Acute lymphocytic leukemia - photomicrograph
Acute lymphocytic leukemia - photomicrograph

Red blood cells, multiple sickle cells
Red blood cells, multiple sickle cells

Malaria, microscopic view of cellular parasites
Malaria, microscopic view of cellular parasites

Malaria, photomicrograph of cellular parasites
Malaria, photomicrograph of cellular parasites

Red blood cells, sickle cells
Red blood cells, sickle cells

Red blood cells, sickle and pappenheimer
Red blood cells, sickle and pappenheimer

Red blood cells, target cells
Red blood cells, target cells

Formed elements of blood
Formed elements of blood

Blood smear


A blood smear is a blood test that gives information about the number and shape of blood cells.

Alternative Names:

Peripheral smear

How the Test is Performed:

A blood sample is needed.

The blood sample is sent to a lab. There, the lab technician looks at it under a microscope. Or, the blood may be examined by an automated machine. The smear shows the number and kinds of white blood cells (differential ), abnormally-shaped blood cells, and gives a rough estimate of white blood cell and platelet counts.

How to Prepare for the Test:

No special preparation is necessary.

How the Test will Feel:

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed:

This test may be done as part of a general health exam to help diagnose many illnesses. Or, your doctor may order this test if you have signs of any of the following disorders: Any known or suspected blood disorder

Normal Results:

Red blood cells normally are the same in size and color and have a lighter-colored area in the center. The blood smear is considered normal if there is:

  • Normal appearance of cells
  • Normal white blood cell differential

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean:

Abnormal results mean there is an abnormality in the size, shape, color, or coating of the red blood cells (RBCs).

Some abnormalities may be graded on a 4-point scale:

  • 1+ means 25% of cells are affected
  • 2+ means half of cells are affected
  • 3+ means 75% of cells are affected
  • 4+ means all of the cells are affected

Presence of target cells may be due to:

  • Breakdown of red blood cells (decreased osmotic fragility )
  • Deficiency of an enzyme called lecithin cholesterol acyl transferase
  • Abnormalities of hemoglobin , the protein in red blood cells that carry oxygen (hemoglobinopathies)
  • Iron deficiency
  • Liver disease
  • Spleen removal

Presence of sphere-shaped cells (spherocytes) may be due to:

Presence of elliptocytes may be a sign of hereditary elliptocytosis or hereditary ovalocytosis . These are conditions in which RBCs are abnormally shaped.

Presence of fragmented cells (schistocytes) may be due to:

Presence of a type of immature red blood cell called a normoblast may be due to:

  • Cancer that has spread to bone marrow
  • Blood disorder called erythroblastosis fetalis that affects a fetus or newborn
  • Tuberculosis that has spread from the lungs to other parts of the body through the blood (miliary tuberculosis )
  • Disorder of the bone marrow in which the marrow is replaced by scar (fibrous) tissue (myelofibrosis )
  • Removal of spleen
  • Severe breakdown of RBCs (hemolysis )
  • Disorder in which there is excessive breakdown of hemoglobin (thalassemia )

The presence of burr cells (echinocytes) may indicate:

  • Abnormally high level of nitrogen waste products in the blood (uremia )

The presence of spur cells (acanthocytes) may indicate:

  • Inability to fully absorb dietary fats through the intestines (abetalipoproteinemia )
  • Severe liver disease

The presence of teardrop-shaped cells may indicate:

  • Myelofibrosis
  • Severe iron deficiency
  • Thalassemia major

The presence of Howell-Jolly bodies may indicate:

The presence of Heinz bodies may indicate:

  • Alpha thalassemia
  • Congenital hemolytic anemia
  • Disorder in which red blood cells break down when the body is exposed to certain drugs or the stress of infection (G6PD deficiency )
  • Unstable form of hemoglobin

The presence of slightly immature red blood cells (reticulocytes) may indicate:

  • Anemia with bone marrow recovery
  • Hemolytic anemia
  • Hemorrhage

The presence of basophilic stippling may indicate:

  • Anemia caused by bone marrow not producing normal blood cells due to toxins or tumor cells (myelophthisic process)
  • Lead poisoning
  • Myelofibrosis

The presence of sickle cells may indicate sickle cell anemia.


Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

  • Excessive bleeding
  • Fainting or feeling light-headed
  • Hematoma (blood accumulating under the skin)
  • Infection (a slight risk any time the skin is broken)


Bain BJ. The peripheral blood smear. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 160.

Vajpayee N, Graham SS, Bern S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 30.

Review Date: 2/24/2014
Reviewed By: Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Contact Us: 1-800-245-3314 or (501) 329-3831 2302 College Avenue, Conway, Arkansas 72034
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