Hematocrit

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

Table of Contents
Take the Blood Disorders Quiz
Red blood cell picture

Hematocrit (Hct) Levels

This is the ratio of the volume of red cells to the volume of whole blood. Normal range for hematocrit is different between the sexes and is approximately 45% to 52% for men and 37% to 48% for women. This is usually measured by spinning down a sample of blood in a test tube, which causes the red blood cells to pack at the bottom of the tube.

What is the hematocrit?

The hematocrit is the proportion, by volume, of the blood that consists of red blood cells. The hematocrit (hct) is expressed as a percentage. For example, a hematocrit of 25% means that there are 25 milliliters of red blood cells in 100 milliliters of blood.

How is the hematocrit measured?

The hematocrit is typically measured from a blood sample by an automated machine that makes several other measurements of the blood at the same time. Most of these machines in fact do not directly measure the hematocrit, but instead calculate it based on the determination of the amount of hemoglobin and the average volume of the red blood cells. The hematocrit can also be determined by a manual method using a centrifuge. When a tube of blood is centrifuged, the red cells will be packed into the bottom of the tube. The proportion of red cells to the total blood volume can then be visually measured. Continue Reading

Picture of Red Blood Cells
Picture of Red Blood Cells
Reviewed on 10/29/2015
References
Medically reviewed by Avrom Simon, MD; Board Certified Preventative Medicine with Subspecialty in Occupational Medicine

REFERENCE:

Braunwald, Eugene, et al. Harrisons's Principles of Internal Medicine. 17th ed. McGraw-Hill, 2008.

IMAGES:

1.Getty Images

2.Getty Images

3.Getty Images

4.iStock

5.iStock

Subscribe to MedicineNet's Newsletters

Get the latest health and medical information delivered direct to your inbox!

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

VIEW PATIENT COMMENTS

Health Solutions From Our Sponsors