Table of ContentsView AllTable of ContentsBlood VolumeBlood LossBlood ReplacementMeasurement
Table of ContentsView All
View All
Table of Contents
Blood Volume
Blood Loss
Blood Replacement
Measurement
The amount of blood in the human body varies based on age, weight, and sex. An adult male weighing about 200 pounds can have almost 6 liters, or a little over 12 pints, of blood while an adult female weighing about 165 pounds might have 4.3 liters, or about 9 pints, of blood.
The body can manage some blood loss without difficulty. Once blood loss is faster than the body can replace it, the body cango into shock.
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Terminology
Blood volume varies from person to person.How much you weigh, your age, and your sex are all factors that determine an adequate blood volume.
Generally, typical amounts of blood are:
The sex difference in blood volume is largely due to males having more lean body mass compared to more adipose (fat) tissue in females.
Is Blood Blue?
How Much Blood Can the Body Lose?
For minimal blood loss, the body can usually replace the blood volume without much impact. Larger losses of blood volumecan be a medical emergencyand require lifesaving interventions such as a blood transfusion.
The American College of Surgeons developed criteria to classify blood volume loss.This classification was developed based on an otherwise healthy 70 kilogram, or 154-pound, individual. The various classes of blood loss also include signs and symptoms that are likely to be present:
Hemoglobin levelsvary based on sex:
The Association for the Advancement of Blood & Biotherapies (AABB) worked with a panel of experts to recommend that if hemoglobin levels drop below the acceptable range and the individual with a low hemoglobin is having symptoms as described above, a healthcare provider can consider many treatment options, including a blood transfusion.
Blood Loss Treatment OptionsSeveral interventions can helpstop blood loss. Applying direct pressure to the wound, pressure above the wound with atourniquet, or use of medications specifically designed to increase clotting are all methods that can be used to stop bleeding.Intravenous fluids or plasma transfusion may help stabilize blood volume if it has dropped significantly.Blood transfusionmay be needed if hemoglobin levels drop too low. This may be a whole blood transfusion or apacked red blood cell transfusion.Component transfusion of platelets may also be needed.
Blood Loss Treatment Options
Several interventions can helpstop blood loss. Applying direct pressure to the wound, pressure above the wound with atourniquet, or use of medications specifically designed to increase clotting are all methods that can be used to stop bleeding.Intravenous fluids or plasma transfusion may help stabilize blood volume if it has dropped significantly.Blood transfusionmay be needed if hemoglobin levels drop too low. This may be a whole blood transfusion or apacked red blood cell transfusion.Component transfusion of platelets may also be needed.
Several interventions can helpstop blood loss. Applying direct pressure to the wound, pressure above the wound with atourniquet, or use of medications specifically designed to increase clotting are all methods that can be used to stop bleeding.
Intravenous fluids or plasma transfusion may help stabilize blood volume if it has dropped significantly.
Blood transfusionmay be needed if hemoglobin levels drop too low. This may be a whole blood transfusion or apacked red blood cell transfusion.Component transfusion of platelets may also be needed.
How Does the Body Make More Blood?
The bone marrow makes blood cells, a process calledhematopoiesis.Stem cells in the bone marrow differentiate to produce the cellular components of blood:
Peritubular cells in the kidneys are sensitive to oxygen levels in the blood. If the cells sense a decrease (such as due to blood loss), they secrete the hormoneerythropoietin.This signals the bone marrow to make more red blood cells.
Ironis needed to produce hemoglobin in red blood cells, so the body taps into iron stores and increases the amount it absorbs from the diet.
Other chemical messengers in the body signal the bone marrow to produce more platelets and white blood cells when they are low.
However, it takes weeks for the marrow to replace any cellular component. If blood loss is too rapid, a transfusion may be needed.
Plasmais the liquid part of blood. When blood is lost, plasma is replenished from the body’s store of liquid.If blood volume is lost, fluids need to be replaced (orally or intravenously) to restore plasma levels. The kidneys also respond to reduce the loss of fluids and maintain plasma volume.
Plasma is replaced relatively rapidly in the body. For example, a person candonate plasmatwice weekly, as long as there are 48 hours between donations.
Why Do People Need Blood Transfusions?
Using Blood Volume to Arrive at a Diagnosis
Determining blood volume status can be an important part of a healthcare provider’s ability to make a diagnosis and determine the most effective treatments.Blood volume can be important in various diseases, such as shock due to blood loss ordecompensated heart failure.
Blood volume assessment can involve:
More specialized methods include:
Summary
Blood volume varies based on age. weight and sex. An adult male who is about 6 feet tall and weighs about 200 pounds has about 12 pints of blood. The bone marrow produces the cellular components of blood—red blood cells, white blood cells, and platelets.
Medical interventions, such as blood transfusions, might be needed if bleeding reduces blood volume significantly, which can produce shock. Laboratory testing and physical examination can determine the extent of blood loss and what interventions are needed.
13 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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