Close
New

Medscape is available in 5 Language Editions – Choose your Edition here.

 

Hemoglobin Concentration (Hb) 

  • Author: Brian Yang Merritt, MD; Chief Editor: Eric B Staros, MD  more...
 
Updated: Feb 12, 2014
 

Reference Range

The reference ranges for hemoglobin concentration in adults are as follows:[1]

  • Men: 14.0-17.5 (mean 15.7) g/dL
  • Women: 12.3-15.3 (mean 13.8) g/dL

The reference ranges for hemoglobin concentration in children are as follows:[2]

  • Birth: mean 16.5 g/dL (-2SD: 13.5 g/dL)
  • 1-3 days: mean 18.5 g/dL (-2SD: 14.5 g/dL)
  • 1 week: mean 17.5 g/dL (-2SD: 13.5 g/dL)
  • 2 weeks: mean 16.5 g/dL (-2SD: 12.5 g/dL)
  • 1 month: mean 14.0 g/dL (-2SD: 10.0 g/dL)
  • 2 months: mean 11.5 g/dL (-2SD: 9.0 g/dL)
  • 3-6 months: mean 11.5 g/dL (-2SD: 9.5 g/dL)
  • 0.5-2 years: mean 12.0 g/dL (-2SD: 11.0 g/dL)
  • 2-6 years: mean 12.5 g/dL (-2SD: 11.5 g/dL)
  • 6-12 years: mean 13.5 g/dL (-2SD: 11.5 g/dL)
  • 12-18 years female: mean 14.0 g/dL (-2SD: 12.0 g/dL)
  • 12-18 years male: mean 14.5 g/dL (-2SD: 13.0 g/dL)

Reference ranges may vary depending on the individual laboratory, instruments, and methods.

Next

Interpretation

Low hemoglobin

Hemoglobin concentration (Hb) is used clinically to determine the presence of anemia, which is functionally defined as insufficient red blood cell (RBC) mass to adequately deliver oxygen to peripheral tissues.[3] Anemia is considered to be present if the Hb or the hematocrit (Hct) is below the lower limit of 2 standard deviations (-2SD) or the 95% confidence interval for the normal population.[4, 5, 6] This definition of anemia results in 2.5% of normal individuals being classified as anemic.[5, 6] Anemia is absolute if the RBC mass is decreased and relative if associated with an increased plasma volume.[5]

Absolute anemia can be divided into 2 main categories: decreased RBC production and increased RBC destruction or loss in excess of the bone marrow’s ability to replace those losses. Causes of the first category include nutritional deficiencies (iron, folate, vitamin B12, vitamin B6), anemia of chronic disease, renal, liver, or endocrine disease, bone marrow infiltration (myelophthisic anemia), aplastic anemia, pure red cell aplasia, and sideroblastic anemia. Causes of the second category include blood loss (hemorrhage), hemolysis of various etiologies (both intrinsic and extrinsic), and hemoglobin disorders (hemoglobinopathies and thalassemias).[5, 7]

Relative anemia, on the other hand, may be seen in overhydration (volume overload), pregnancy, macroglobulinemia, and in postflight astronauts.[5, 7]

High hemoglobin

Higher-than-normal Hb may be indicative of polycythemia. The World Health Organization (WHO) classification of hematologic malignancies defines polycythemia as Hb greater than 18.5 g/dL in men, greater than 16.5 g/dL in women, Hct greater than 99th percentile of the method-specific reference range, or Hb greater than 17 g/dL in men, greater than 15 g/dL in women with a documented and sustained increase of at least 2 g/dL from baseline not attributed to correction of iron deficiency.[5, 8]

Absolute polycythemia is an increase in the total RBC mass in the body. Causes include hypoxia, inappropriate erythropoietin production, genetic polycythemia, and polycythemia vera. Relative polycythemia is an increase in Hct or RBC count resulting from a decrease in plasma volume; however, total RBC mass is not increased. Causes include dehydration, shock, diuretic therapy, and spurious polycythemia (Gaisböck syndrome).[5, 7]

Previous
Next

Collection and Panels

See the list below:

  • Specimen: Whole blood, usually collected by venipuncture
  • Collection: EDTA tube (purple/lavender top; see image below) containing EDTA potassium salt additive as an anticoagulant
    Whole blood tube with lavender closure and EDTA po Whole blood tube with lavender closure and EDTA potassium salt additive.
  • Panels: Complete blood count (CBC), hemoglobin and hematocrit (Hb/Hct)
Previous
Next

Background

Description

Hemoglobin is the main component of red blood cells and serves as the transporter for oxygen and carbon dioxide in the blood. Hemoglobin concentration (Hb) is usually reported as grams of hemoglobin per deciliter of blood (g/dL).[1, 9]

Hb is commonly measured by the cyanhemoglobin (hemoglobin cyanide) method. A sample of blood is diluted in a solution of potassium ferricyanide and potassium cyanide, which oxidizes hemoglobin to hemiglobin (Hi; methemoglobin) and then converts it to hemoglobin cyanide (HiCN). The concentration of HiCN is then measured by spectrophotometry. The absorbance of the solution at 540 nm reflects the amount of hemoglobin present. A standard HiCN solution is also used for comparison. All forms of hemoglobin are detected except sulfhemoglobin (SHb).[1, 9]

Automated blood cell counters usually measure hemoglobin concentration by a modified cyanmethemoglobin or an alternate lauryl sulphate method.[10] With automated methods, the precision coefficient of variation for determining Hb is less than 1%.[11]

Indications/Applications

As part of a standard CBC, the Hb can be used to determine the presence of anemia or polycythemia. Measurement of Hb as part of Hb/Hct can also be used to determine an appropriate increase after red blood cell transfusion. In an adult patient, the Hb is usually expected to rise by 1 g/dL after transfusion of one unit of packed red blood cells (pRBCs).[12]

The measurement of Hb is generally considered accurate and more useful than Hct or RBC count for the diagnosis of anemia. Hb is measured directly, whereas Hct in some automated instruments is measured indirectly, calculated from the product of the RBC count times the mean corpuscular volume (MCV). Thus, factors that spuriously affect the RBC count (such as RBC clumping) and/or the MCV (such as prolonged storage) will ultimately affect the Hct measurement. Hb is also preferred because among these laboratory parameters, it is the best indicator of the oxygen carrying capacity in the blood.[10]

Although measuring the RBC mass in the body can also be an accurate method for determining anemia or polycythemia, these methods require radiolabeling of red cells or human serum albumin and are time consuming, difficult to perform, and expensive. Furthermore, Hb and Hct, which are much more readily available in medical laboratories, have been shown to correlate with RBC mass measurements.[13]

Considerations

Normal ranges for Hb vary among men and women (with different values for pregnancy), different age groups, different altitudes, and cigarette smokers.[4] Also, the aging process in adults is responsible for some mild Hb changes, such as a 1 g/dL decrease in healthy men between the ages of 70 to 88 years, partly due to decreased androgens as well as age-related decreased stem cell proliferation, which is seen in both men and women.[2, 3] Therefore, values should always be interpreted in context of established reference ranges for each individual.

Factors that cause changes in the plasma volume, without changes in the overall RBC mass, can also affect the Hb and may lead to the presence of relative anemia or relative polycythemia.

Hb is typically measured spectrophotometrically, and erroneously high results may be seen with increased sample turbidity due to hyperlipidemia, abnormal plasma proteins, large numbers of leukocytes, hemolysis, abnormal hemoglobins, or nucleated red blood cells.[1, 14] However, newer automated instruments are able to identify and minimize this type of interference.[10]

Previous
 
Contributor Information and Disclosures
Author

Brian Yang Merritt, MD Fellow in Hematopathology and Molecular Genetic Pathology, Department of Pathology and Immunology, Baylor College of Medicine

Brian Yang Merritt, MD is a member of the following medical societies: American Society for Clinical Pathology, American Society of Hematology, College of American Pathologists, United States and Canadian Academy of Pathology, Society for Hematopathology, European Association for Haematopathology

Disclosure: Nothing to disclose.

Coauthor(s)

Choladda Vejabhuti Curry, MD Assistant Professor of Pathology and Immunology, Baylor College of Medicine; Hematopathologist and Cytopathologist, Section of Hematopathology, Texas Children's Hospital

Choladda Vejabhuti Curry, MD is a member of the following medical societies: American Society for Clinical Pathology, American Society of Cytopathology, American Society of Hematology, College of American Pathologists, United States and Canadian Academy of Pathology, Society for Hematopathology, European Association for Haematopathology, International Clinical Cytometry Society

Disclosure: Nothing to disclose.

Chief Editor

Eric B Staros, MD Associate Professor of Pathology, St Louis University School of Medicine; Director of Clinical Laboratories, Director of Cytopathology, Department of Pathology, St Louis University Hospital

Eric B Staros, MD is a member of the following medical societies: American Medical Association, American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology

Disclosure: Nothing to disclose.

References
  1. Vajpayee N, Graham SS, Bem S. Basic Examination of Blood and Bone Marrow. McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Saunders, an imprint of Elsevier Inc; 2011. Chap 30:509-35.

  2. Marks PW, Glader B. Approach to Anemia in the Adult and Child. Hoffman F, Benz EJ, Shattil SJ, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, PA: Churchill Livingstone; 2009. Chap 34:439-46.

  3. Means RT, Glader B. Disorders of Red Cells. Greer JP, Foester J, Rodgers GM, et al, eds. Wintrobe's Clinical Hematology. 12th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009. Chap 26.

  4. Centers for Disease Control and Prevention. Recommendations to prevent and control iron deficiency in the United States. MMWR. 1998. 47(No. RR-3):1-29.

  5. Elghetany MT, Banki K. Erythrocytic Disorders. McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Saunders, an imprint of Elsevier Inc; 2011. Chap 32:557-600.

  6. Brugnara C, Oski FA, Nathan DG. Diagnostic Approach to the Anemic Patient. Orkin SH, Nathan DG, Ginsburg D, et al, eds. Nathan and Oski’s Hematology of Infancy and Childhood. 7th ed. Philadelphia, PA: Saunders, an imprint of Elsevier Inc; 2009. Chap 10:455-66.

  7. Hemoglobin. A.D.A.M. Medical Encyclopedia. Atlanta, GA: A.D.A.M., Inc; 1997-2014. Updated February 8, 2012. Available at http://www.nlm.nih.gov/medlineplus/ency/article/003645.htm. Accessed: February 1, 2014.

  8. Thiele J, Kvasnicka HM, Orazi A, et al. Polycythaemia Vera. Swerdlow SH, Campo E, Harris NL, et al, eds. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues. Lyon, France: IARC; 2008. 40-3.

  9. Mais DD. Hematopathology. ASCP Quick Compendium of Clinical Pathology. 2nd ed. Chicago, IL: American Society for Clinical Pathology; 2009. Chap 4:242-320.

  10. Ryan DH. Examination of Blood Cells. Lichtman MA, Kipps TJ, Seligsohn U, et al, eds. Williams Hematology. 8th ed. New York, NY: The McGraw-Hill Companies, Inc; 2010. Chap 2.

  11. Perkins SL. Examination of the Blood and Bone Marrow. Greer JP, Foester J, Rodgers GM, et al, eds. Wintrobe’s Clinical Hematology. 12th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009. Chap 1.

  12. Davenport RD, Mintz PD. Transfusion Medicine. McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Saunders, an imprint of Elsevier Inc; 2011. Chap 36:731-45.

  13. Sirhan S, Fairbanks VF, Tefferi A. Red cell mass and plasma volume measurements in polycythemia: evaluation of performance and practical utility. Cancer. July 1, 2005. 104(1):213-5. [Medline].

  14. Perkins SL, Hussong JW. Red Blood Cells. Jones SL, ed. Clinical Laboratory Pearls. Philadelphia, PA: Lippincott Williams & Wilkins; 2001. 61-96.

 
Previous
Next
 
Whole blood tube with lavender closure and EDTA potassium salt additive.
 
 
 
All material on this website is protected by copyright, Copyright © 1994-2016 by WebMD LLC. This website also contains material copyrighted by 3rd parties.