Hematocrit Blood Test Activities

Test Procedures and Card Reader Learning Activities

Introduction

The hematocrit test measures the percentage of red blood cells (RBCs) in a blood sample compared to the total blood volume. Red blood cells carry oxygen throughout the body via the bloodstream, delivering it to tissues where it is used to produce ATP (adenosine triphosphate), the immediate energy source for cellular functions. Therefore, the hematocrit test is important for assessing the blood’s ability to carry oxygen and the capacity of cells to perform their functions.

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The hematocrit procedure involves taking a blood sample and placing it into a glass capillary tube. The tube is then centrifuged at high speed for 5 minutes, or the sample can be allowed to stand for 30 to 60 minutes. During this time, the blood components will separate into layers based on their density.

Red Blood Cells (Packed Cell Volume)

Red blood cells, the densest components, settle to the bottom of the hematocrit tube, creating a dark red layer. This layer typically represents:

• Males: 41-50% of blood volume
• Females: 36-44% of blood volume

The Buffy Coat

Above the RBCs, white blood cells (leukocytes) and platelets (thrombocytes) form a narrow band comprising about 1% of the total blood volume. This light-colored layer is known as the buffy coat.

Plasma Layer

The top layer is plasma, a pale yellow fluid (92% water). This layer typically accounts for:

• Males: 49-58% of blood volume
• Females: 50-63% of blood volume

p>Note: Hematocrit levels can deviate from normal due to changes in the number of RBCs, the volume of RBCs, or the volume of plasma.

Activities

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References and Attributions

American Red Cross – “What Does Hematocrit Mean?”

Healthline – “Hematocrit Test.”

OpenStax, Anatomy and Physiology: “An Overview of Blood.” (Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction)

NIH – “Hematocrit.”

NIH – “Hemoglobin and Hematocrit.”

StatPearls – “Hematocrit.”

Wikipedia – “Hematocrit“