How much blood is in the human body and what does it depend on?

Blood is a liquid tissue consisting of plasma and shaped elements. In a plasma that is a colorless liquid, there are cells in the suspended state: leukocytes, platelets, erythrocytes. The latter give it a characteristic red color. The state of health depends not only on the composition of the blood, but also on how much it is contained in the human body.

Plasma is about 60% of the total. If you separate it from the uniform elements, then it will consist of water by 90%, the remaining 10% - salts, carbohydrates, proteins, carbon dioxide, oxygen, bioactive substances. In men, the plasma is always greater than that of the fairer sex.


Blood performs the most important functions in the human body. It constantly circulates in a system consisting of large and small blood vessels that permeate all organs and tissues, except for the epithelium of the skin and mucous membranes, articular cartilage, eye cornea, hair and nails.

Red cells are involved in the delivery of oxygen to tissues due to the ability of hemoglobin to reversibly bind to its molecules. Platelets take a direct part in clotting during bleeding: they rush to the site of damage to the vessel and form a thrombus on this site. Leukocytes are the main defenders of the body from internal and external harmful agents.

Blood carries oxygen from the lungs to the tissue cells, and carbon dioxide from the tissues to the lungs, transports metabolic products, nutrients, hormones, enzymes, biologically active substances, and is responsible for delivering the final exchange products to the excretory system. It regulates the temperature and maintains the water-electrolyte and acid balance in the body.

How much blood does a person have?

Different people have different volumes. It depends on gender, age, weight and individual characteristics. For the norm, the value is taken - from 5 to 9% of the body weight. On average, about 5-6 liters of blood circulates in an adult person, the child, accordingly, is less. Its quantity is maintained by the body at one level. With deviations in one direction or another, health problems arise.

With a sharp decrease in blood volume, blood pressure drops, anemia, necrosis may develop, brain activity may be disturbed. The loss of two or three liters in a short period of time can result in the death of a person. As a rule, with the loss of half the volume, 98% of people die.

If the system circulates an increased amount, nosebleeds may occur. Cuts and other injuries in this case heal longer, which is associated with greater pressure, under which blood flows out of the wound. As a rule, with the formation of excess blood in the body, its redistribution occurs. It enters the muscle tissue, the skin, is processed by the kidneys and is excreted outward naturally.

In the body, men constantly circulate about 5-6 liters, in women - about 4-5 liters. In the body of a child, its volume is much less than that of an adult, and depends on weight and age. Its amount can change periodically, which is associated with bleeding, significant physical exertion, trauma, menstruation, consumption of large amounts of fluid. Women suffer loss of blood much easier than men.

How to determine the amount of blood in a person?

For this purpose, a certain amount of contrast medium, usually a harmless dye, is injected into the blood. Once it is distributed throughout the channel, make a fence to determine its concentration.

Another way is to introduce radioactive isotopes and count the number of red blood cells in which they are contained. The amount of blood is determined by the level of its radioactivity.

Packages with donor blood
To normalize the volume of blood in the body using blood transfusion

How to make up for the loss?

Today this problem is solved with the help of blood transfusion. This procedure is necessary for severe injuries, surgical operations, childbirth. Most often, plasma is poured, which is about 60% of the total volume. The blood of the donor must necessarily fit the patient in the group and the Rh factor.

According to the existing law, you can donate blood at one time not more than 450 ml( or 600 ml of plasma).In addition, there are restrictions on the frequency of delivery and the weight of the donor( 4 times a year for women, 5 times for men, a gap between fences of at least 60 days, the weight of the donor is not less than 50 kg).This order is due to the fact that a loss of 10% of blood can lead to poor health and the development of anemia.


Human health depends not only on blood composition, but also on its volume. A significant decrease in its amount in the body can cause diseases and even death.