Blood Smear
Testing.com is fully supported by readers. We may earn a commission through products purchased using links on this page. You can read more about how we make money here.
- Also Known As:
- Peripheral Smear
- Blood Film
- Manual Differential
- Differential Slide
- Red Blood Cell Morphology
- Erythrocyte Morphology
- Leukocyte Differential
- Formal Name:
- Peripheral Blood Smear

This page was fact checked by our expert Medical Review Board for accuracy and objectivity. Read more about our editorial policy and review process.
.-
1
Order Your Test
Online or over the phone
-
2
Find a Lab Near You
Over 3,500 locations to choose from
-
3
Get Your Results
Sent Directly to You
At a Glance
Why Get Tested?
To evaluate your red blood cells (RBCs), white blood cells (WBCs), and platelets, to distinguish between the different types of WBCs, and to determine their relative percentages in the blood; to help detect, diagnose, and/or monitor a range of deficiencies, diseases, and disorders involving blood cell production, function, and lifespan
When To Get Tested?
When complete blood count (CBC) and/or automated WBC differential results are abnormal or when you have signs and symptoms that a health care practitioner suspects are due to a condition affecting your blood cells
Sample Required?
A blood sample drawn from a vein in your arm or by pricking a finger or, in the case of an infant, a heelstick
Test Preparation Needed?
None
What is being tested?
A blood smear is a drop of blood spread thinly onto a glass slide that is then treated with a special stain and the blood cells on the slide are examined and evaluated. Traditionally, trained laboratorians have examined blood smears manually using a microscope. More recently, automated digital systems have become available to help analyze blood smears more efficiently.
A blood smear is a snapshot of the cells that are present in the blood at the time the sample is obtained. The blood smear allows for the evaluation of these cells:
- White blood cells (WBCs, leukocytes) — help fight infections or participate in immune responses
- Red blood cells (RBCs, erythrocytes) — carry oxygen to tissues
- Platelets (thrombocytes) — small cell fragments that are vital to proper blood clotting
These cell populations are produced and mainly mature in the bone marrow and are eventually released into the bloodstream as needed. The number and type of each cell present in the blood is dynamic but is generally maintained by the body within specific ranges.
The drop of blood on the slide used for a blood smear contains millions of RBCs, thousands of WBCs, and hundreds of thousands of platelets. A blood smear examination:
- Compares the WBCs’ size, shape, and general appearance to the established appearance of “normal” cells. It also determines the five different types of WBCs and their relative percentages (manual WBC differential).
- Evaluates the size, shape, and color (indicators of hemoglobin content) of the RBCs (RBC morphology)
- Estimates the number of platelets present
A variety of diseases and conditions can affect the number and appearance of blood cells. Examination of the blood smear can be used to support findings from other tests and examinations. For example, RBCs that appear smaller and paler than normal may support other results that indicate a type of anemia. Similarly, the presence of WBCs that are not fully mature may add to information from other tests to help make a diagnosis of infection, malignancy, or other conditions.
Common Questions
Details on Red Blood Cell Irregularities (RBC morphology)
Details on White Blood Cells
Health Professionals – LOINC
LOINC Observation Identifiers Names and Codes (LOINC®) is the international standard for identifying health measurements, observations, and documents. It provides a common language to unambiguously identify things you can measure or observe that enables the exchange and aggregation of clinical results for care delivery, outcomes management, and research. Learn More.
Listed in the table below are the LOINC with links to the LOINC detail pages. Please note when you click on the hyperlinked code, you are leaving Testing.com and accessing Loinc.org.
LOINC | LOINC Display Name |
---|---|
710-4 | Blood smear finding positive LM Nom (Bld) |
5909-7 | Blood smear finding LM Nom (Bld) |
58445-8 | Manual differential comment Nar (Bld) [Interp] |
50957-0 | Manual differential performed Ql (Bld) |
48705-8 | WBC+Platelets Nom (Bld) |
79427-1 | Platelets LM.HPF (Bld) [#/Area] |
9317-9 | Platelets LM Ql (Bld) |
6742-1 | RBC morphology finding Nom (Bld) |
53974-2 | Erythrocyte morphology LM Nar (Urine sed) [Interp] |
18225-3 | RBC shape Nom (Bld) |
18226-1 | RBC size Nom (Bld) |
View Sources
Sources Used in Current Review
Genzen, J. and Lehman, C. (2018 May, Updated). HELLP Syndrome Aplastic Anemia. ARUP Consult. Available online at https://arupconsult.com/content/hellp-syndrome. Accessed on 6/02/18.
Braden, C. (2017 August 2, Updated). Neutropenia. Medscape Hematology. Available online at https://emedicine.medscape.com/article/204821-workup#c11. Accessed on 6/02/18.
Cle, D. (2017 October). Blood film in the era of streaming cells. Rev Bras Hematol Hemoter. 2017 Oct-Dec; 39(4): 295–296. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5693265/. Accessed on 6/02/18.
Comar, S. et. Al. (2017 July 31). Evaluation of criteria of manual blood smear review following automated complete blood counts in a large university hospital. Rev Bras Hematol Hemoter. 2017 Oct-Dec; 39(4): 306–317. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5693276/. Accessed on 6/02/18.
Adewoyin, A. and Nwogoh, B. (2014 December). PERIPHERAL BLOOD FILM – A REVIEW. Ann Ib Postgrad Med. 2014 Dec; 12(2): 71–79. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4415389/. Accessed on 6/02/18.
Gulati, G. et al. (2013 January). Purpose and Criteria for Blood Smear Scan, Blood Smear Examination, and Blood Smear Review. Ann Lab Med. 2013 Jan; 33(1): 1–7. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3535191/. Accessed on 6/02/18.
Bain, B. (2005 August 4). Diagnosis from the Blood Smear. N Engl J Med 2005; 353:498-507. Available online at https://www.nejm.org/doi/full/10.1056/NEJMra043442. Accessed on 6/02/18.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Tabers Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Elstrom, R. (2001 October 28, Reviewed). Peripheral smear. University of Pennsylvania Health System, pennhealth.com [On-line information]. Available online at http://www.pennhealth.com/ency/article/003665.htm.
Biology of Blood. The Merck Manual Home Edition [On-line information]. Available online at http://www.merck.com/mrkshared/mmanual_home/sec14/152.jsp.
Peripheral smear. Robert Wood Johnson University Hospital, Medical Encyclopedia [On-line information]. Available online at http://www.rwjuhh.net/Atoz/encyclopedia/article/003665.asp.
Cutler, C. (2003 September 14). Blood smear. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003665.htm
Brose, M, Updated (2003 May 08, Updated). MedlinePlus Health Information, Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003657.htm
Blackwell, S. and Hendrix, P. (2001). Common Anemias: What Lies Beneath. Clinician Reviews 11(3):53-62 [On-line journal]. Available online at http://www.medscape.com/viewarticle/436692.
(2001 October 15 ). Anemia in Children. American Family Physician, 64:1379-86 [On-line journal]. Available online at http://www.aafp.org/afp/20011015/1379.html.
Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby’s Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 174-176.
Levin, M. (2007 March 9). Blood Differential. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003657.htm. Accessed on 4/10/07.
Dowshen, S. (2007 March). Blood. Nemours Foundation, Teens Health [On-line information]. Available online at http://kidshealth.org/teen/your_body/body_basics/blood.html. Accessed on 4/10/07.
Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. Henry’s Clinical Diagnosis and Management by Laboratory Methods, 21st ed. Richard McPherson and Matthew Pincus, eds. Saunders Elsievier: Philadelphia. Pp 457-483, 2007.
Bell A, Sallah S. The Morphology of Human Blood Cells, 7th ed. 2005. Abbott, Pp 1-27.
Henry’s Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007, Pp 468-478, 505-516, 539-541,549-559.
(August 4, 2005) Bain B. Diagnosis from Blood Smear, Review article. N Engl J Med 2005; 353:498-507. Available online at http://www.nejm.org/doi/pdf/10.1056/NEJMra043442. Accessed February 2011.
(September 9, 2009) Harper J. Pediatric Megaloblastic Anemia. eMedicine article. Available online at http://emedicine.medscape.com/article/959918-overview. Accessed February 2011.
(September 9, 2009) Artz A. Anemia in Elderly Persons. eMedicine article. Available online at http://emedicine.medscape.com/article/1339998-overview. Accessed February 2011.
(February 29, 2010) Dugdale D. Blood Smear. MedlinePlus Medical Encyclopedia. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003665.htm. Accessed February 2011.
Riley R, et.al. How to Prepare and Interpret Peripheral Blood Smear. Medical College of Virginia, Virginia Commonwealth University. Available online at http://www.pathology.vcu.edu/education/PathLab/pages/hematopath/pbs.html. Accessed February 2011.
Gersten, T. (Updated 2012 February 8). Blood smear. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003665.htm. Accessed July 2014.
Schick, P. (Updated 2013 February 21). Hemolytic Anemia. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/201066-overview. Accessed July 2014.
Curry, C. (Updated 2012 August 1). Differential Blood Count. Medscape Drugs and Diseases [On-line information]. Available online at http://emedicine.medscape.com/article/2085133-overview#showall. Accessed July 2014.
Lichtin, A. (Updated 2013 September). Evaluation of Anemia. Merck Manual for Healthcare Professionals [On-line information]. Available online through http://www.merckmanuals.com. Accessed July 2014.
Gauer, R. and Braun, M. (2012 May 15). Thrombocytopenia. Am Fam Physician. 2012 Mar 15;85(6):612-622. [On-line information]. Available online at http://www.aafp.org/afp/2012/0315/p612.html. Accessed July 2014.
(© 1995–2014). Morphology Evaluation (Special Smear). Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/print/9184. Accessed July 2014.
(2012 May 18). What is Anemia? National Heart Lung and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/health-topics/topics/anemia/. Accessed July 2014.
Lynch, E. (© 1990) Chapter 155 Peripheral Blood Smear. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. NCBI Bookshelf [On-line information]. Available online at http://www.ncbi.nlm.nih.gov/books/NBK263/. Accessed July 2014.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 168-170.
Ask a Laboratory Scientist
