A blood smear is a blood test that gives information about the number and shape of blood cells. It is often done as part of or along with a complete blood count (CBC).
Peripheral smear; Complete blood count - peripheral; CBC - peripheral
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 provides this information:
No special preparation is necessary.
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.
This test may be done as part of a general health exam to help diagnose many illnesses. Or, your health care provider may recommend this test if you have signs of:
A blood smear may also be done to monitor the side effects of chemotherapy or to help diagnose an infection, such as malaria.
Red blood cells (RBCs) normally are the same size and color and are a lighter color in the center. The blood smear is considered normal if there is:
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
Abnormal results mean the size, shape, color, or coating of the RBCs is not normal.
Some abnormalities may be graded on a 4-point scale:
Presence of cells called target cells may be due to:
Presence of sphere-shaped cells may be due to:
Presence of fragmented cells (also called schistocytes) may be due to:
Presence of a type of immature RBCs called normoblasts may be due to:
The presence of cells called burr cells may indicate:
The presence of cells called spur cells may indicate:
The presence of teardrop-shaped cells may indicate:
The presence of Howell-Jolly bodies (a type of granule inside the red blood cells) may indicate:
The presence of Heinz bodies (bits of altered hemoglobin) may indicate:
The presence of slightly immature RBCs may indicate:
The presence of basophilic stippling (a spotted appearance) may indicate:
The presence of sickle cells may indicate sickle cell anemia.
There is little risk involved with having your blood taken. 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:
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Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.