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How many liters of blood are in the human body? The amount of blood in the body of an adult: how to calculate and basic functions Volume cr


This article is co-written by Shari Forschen, NP. Shari Forshen is a registered nurse at the Sanford Health Nonprofit Medical Organization in North Dakota. She received a master's degree in family paramedic from the University of North Dakota. Has been working as a nurse since 2003.

The number of sources used in this article is 18. You will find a list of them at the bottom of the page.

There are a large number of reasons when a doctor may need to calculate the amount of circulating blood, for example, before an operation, to count the anesthesia or to count the amount of blood in a donation. Blood volume can be calculated in various ways, and each of them gives different results, which, however, are not very different.

How much is in the human body?

In approximately 4-5 liters of blood. Blood makes up about 6-8% of the total body weight. In an adult, the heart pumps about 10,000 liters of blood per day. In one stroke, approximately 130 milliliters are thrown into the aorta. The kidneys process about 180 liters of blood daily, but less than 1% is excreted in the form of urine. The amount of total blood volume may vary depending on the physical condition, climatic and hormonal factors. For example, in sports, the blood volume may exceed 7 liters.

In men, the blood volume is 77 ml / kg of weight, and in women - 65 mg / kg. This difference is due to the fact that women have more adipose tissue. How many liters of blood in a person is not the most important parameter of the quality of his life, in many respects the level of health depends on the number of blood cells.

A few definitions

Blood - liquid connective tissue that fills the cardiovascular system of vertebrates, including humans and some invertebrates. It consists of the liquid part of the plasma and the formed elements: leukocyte cells and post-cell structures: red blood cells, and platelets. It circulates through the vascular system under the action of the force of a rhythmically contracting heart and does not communicate directly with other body tissues due to the presence of histohematological barriers. Blood consists of two main components - plasma and suspended in it shaped elements . From the point of view of colloid chemistry, blood is a polydisperse system - a suspension of red blood cells in plasma. The average amount of blood in the body of an adult is 6-8% of the total mass, or 65-80 ml of blood per 1 kg of body weight, and in the body of a child - 8-9%. That is, the average blood volume in an adult male is 5000-6000 ml.

White blood cells - white blood cells, a heterogeneous group of human or animal blood cells that are different in appearance and function, isolated on the basis of the lack of independent coloring and the presence of a nucleus. An important contribution to the study of the protective properties of leukocytes was made by Ilya Mechnikov and Paul Erlich. Mechnikov discovered and studied the phenomenon of phagocytosis, and subsequently developed a phagocytic theory of immunity.

About blood. DNA will tell about age.

Blood is the most important fluid in the human body. The life of people depends on this fluid, and its lack can lead to loss of consciousness and even death. Therefore, people often want to know: how many liters of blood in a person, what is the minimum amount necessary for life?

Before calculating the amount, you should find out what components it consists of and where in the body it is. This is not just a liquid, but a special type of connective tissue that circulates throughout the body, delivering nutrients to different parts of the body and removing the waste products of the body. It consists of two main components:

  • plasma (liquid part),
  • shaped elements (red blood cells, platelets and white blood cells).

The plasma volume in the body of an adult healthy person is 50-60% of the BCC (circulating blood volume), of the formed elements - 40-50%. But these figures are approximate - the exact ratio of plasma to the rest is determined individually.

The shaped elements consist of three types of bodies:

  • red blood cells (red),
  • white blood cells (white),
  • platelets (platelets).

The former perform a transport function - they combine with oxygen and deliver it from the lungs to all organs and tissues. By giving up oxygen, red blood cells simultaneously attach carbon dioxide, transferring it back to the lungs. White blood cells are a protective system of the body, they destroy bacteria and other foreign bodies. Platelets are a “patch”, blood platelets that clog a person’s wounds and cuts. Platelet deficiency can lead to impaired blood coagulation.

The blood is distributed unevenly throughout the body, located in two different systems. About half circulates through the body from arterial vessels to venous (and so on in a circle). The second half is contained in one of the storage organs - the blood depot - the spleen, liver or skin.

Important! Blood vessels are also unevenly distributed throughout the vessels. Approximately 73-75% of it is contained in the veins (therefore damage to these vessels is so dangerous), about 20% is in the arteries, only 5-7% - in the capillaries.

How much blood is in the human body

The approximate amount of blood - the figure is quite inaccurate, can vary depending on various factors. Gender, age, physical fitness, nutrition, pregnancy (in expectant mothers, the volume is higher due to the general circulatory system with the child) strongly affect the average.

Exactly the total amount is measured by introducing radioactive isotopes into the body and counting the red blood cell count. According to studies, the average numbers are:

  • in men - 5-6 liters,
  • a woman - 4-4.5 liters,
  • in children (8-10) years old - 2-2.5 liters,
  • in older people - 4-5.5 liters.

Important! The higher the indicator of physical activity, the greater the volume of circulating blood. In people with bed rest, the number of red blood cells decreases by 10-15 percent in two weeks.

How to calculate blood volume yourself

But still these figures are very approximate. After all, the amount of blood in the body depends mainly on the weight of a person, and these calculations are based on average data. How to find out your figure yourself? For this, it is not necessary to go to the clinic - just know your weight and make simple calculations.

So, suppose the weight is 60 kg. The normal percentage of the ratio of blood volume to body weight is from 6 to 9. First, we calculate by extreme indicators. At 6%, this is 3.6 liters, and at 8%, 5.4 liters. Add up the resulting values ​​and divide by 2 - we get 4.5 liters. This is the average amount of blood that can fluctuate depending on various factors.

You can go the other way. The average blood content per kg of weight is 70-75 ml / kg for men and 60-65 ml / kg for women. We multiply this figure by our weight, we get the volume in ml, which must be divided by 1000. But the method does not really matter - the numbers will be approximately equal.

Important! In pregnant women, the volume value per unit mass is greatly increased - 75 ml / kg. This is due to the general circulatory system in the child and mother.

Safe volume for life

Ordinary cuts or scratches are not terrible for human life. Only small vessels are damaged - capillaries, the integrity of which is quickly eliminated by platelets. The threat is only blood loss from large vessels - arteries and veins.

Since almost half of the blood is in stock, a loss of up to 30% of the total circulating blood volume is not considered life-threatening. Losing a third of the BCC can cause sweating, nausea, dizziness and other unpleasant symptoms - but the person will survive. In such a situation, it is recommended to drink a lot to make up the volume of circulating blood - transfusion from the donor is usually not required.

Need to remember! Donation does not pose a health hazard - about 400 ml of blood is given. A healthy person can easily make up for such a loss by ejecting blood into the bloodstream from the depot. The maximum that you can feel is a little dizzy.

Massive blood loss

When a person loses from 30 to 50% of the BCC - this is more serious. A person's skin turns pale, his body becomes colder, and his limbs become bluish from a lack of oxygen. In such a situation, an urgent blood transfusion is necessary - otherwise, loss of consciousness or falling into a coma is possible. The loss of 50% of the volume is already deadly, few experience this. Surviving under such circumstances is only possible if emergency medical care is provided. Death occurs if more than 4 liters (60%) were lost during bleeding.

Important! Women suffer blood loss much better than men, they can survive the loss of even 50% of the bodies. This is due to childbirth, during which they lose up to several hundred milliliters of blood.

Human blood volume is an important indicator that affects health. Heavy bleeding is extremely dangerous, especially if the main arteries or veins are damaged. Therefore, in such a situation, it is necessary to stop the loss of blood with a tourniquet and call a doctor. Be sure to look at the instructions on how to help people with severe bleeding. Later, such skills can save someone's life.

Many people wonder - how many liters of blood in a person? Agree, the question is quite interesting and therefore it is worthwhile to understand it in more detail and in detail, having examined its functions and composition, as well as how the blood loss in the body is restored and most importantly, how much blood is in the human body.

Blood is a fluid that includes plasma and specific shaped components. It is in the plasma of both an adult and a child that contains white blood cells, platelets and red blood cells - the general state of health depends on the normal amount of blood in the human body, which also depends on the quality of blood composition. In particular, the average amount of plasma is 60 percent of the total blood volume in the human body. If uniform components are distinguished from it, then 90% is water and only 10% are salts and carbohydrates, proteins and, according to statistics, the amount of plasma in a man’s body is slightly larger than that of a woman.

At the very beginning, it is blood, or rather the red bodies that make up its composition, that supply oxygen to organs and tissues - all this happens due to the property of hemoglobin to bind molecules together. And therefore, depending on how many liters of blood in a person, the saturation of tissues, organs and the whole body with oxygen depends. The platelet takes an active part in the process of blood coagulation in case of bleeding, rushing to the site of injury and forming a blood clot in the vessel. At the same time, white blood cells in the body of an adult and a baby are the main defenders in the body from external and internal counterparties.

Blood also supplies oxygen from the lungs, where it is enriched in it into cells, tissues and organs, and in return - removes carbon dioxide as an metabolic product of human organs. The blood also perfectly regulates the temperature regime of the body and helps maintain the oxygen balance in the human body - in case of insufficiency in the human body, the latter experiences general weakness, as well as cold in the extremities and, in the worst case, the development of anemia, including deaths.

If we talk about this, then at the very beginning it is worth saying that this volume is purely individual. It can depend on gender, weight category, when in the human body is 50 or 70 or 100 kg, age and other personal properties of the body and varies from 5 to 9 percent of the total body weight.

On average, 5-6 liters are present in the body of an adult, and in a baby this indicator is less - it is her “displacement” that helps maintain the entire human body at the same level, and with anomalies in the direction of increase or decrease, a person may begin certain problems with own health. In the worst case scenario, such a situation can be fatal.

For example, if the blood in the body is more than normal, the person may experience nosebleeds, and cuts, injuries and other injuries heal longer, because the pressure of the resulting blood in this case is somewhat higher. With an excessive amount of blood in the body, it is redistributed to the skin, muscles and, processed by the kidneys, is excreted from the body through natural excretory pathways.

Speaking in more detail, then for a man - this indicator is fixed at the level of 5-6 liters of blood, for women - 4-5 liters, and for a child even less, depending on age and weight. This figure may vary depending on physical exertion or trauma, a woman’s menstrual cycle, or other factors, while women tolerate blood loss more easily than a stronger sex.

The maximum possible and permissible blood loss

If we talk about emergency cases, then if an individual loses about 2-3 liters of blood within a short period of time, such a loss can be fatal. In this case, blood loss can lead to the development of a disease such as anemia.

It is also worth noting the fact that for some types of diseases it is necessary to systematically transfuse blood and this is not a good moment in relation to normal human life. If we are talking about surgery, then with surgical intervention, with a standard procedure for a person, appropriate transfusion may be required ranging from 5 to 8 liters.

Each person understands perfectly well that no matter how many liters of blood is in his body, blood loss is always undesirable and in some cases even harmful. However, this problem can be solved by transfusion of the latter from the donor. In particular, this approach is practiced in severe injuries, as well as during surgery or during childbirth. At the same time, plasma is transfused to the patient - it is it that makes up the entire volume of 60 percent and it should be similar in group, and the compatibility of the Rh factor.

According to the current norms of the law, it is worth noting that if we are talking about blood donation, then for 1 delivery the doctor can make a fence - a maximum of 450 ml. blood or not more than 600 ml. plasma for one change from one patient. The law also prescribes certain requirements for the frequency of delivery, as well as the body weight of a potential donor. Here the frequency is 4 changes for women and 5 for men per year, with an interval of 2 months between each given medical procedure. If we are talking about the weight category of a potential donor, then it should be at least 50 kg and the approach itself and such restrictions are due to the fact that even the loss of 1/10 of the blood leads to the possible development of anemia and a deterioration in the general condition and well-being.

How is blood volume determined

First of all, an established contrast agent is injected into the blood, for the most part it is a dye that is not harmful to the body. After it is completely distributed throughout the body - they take blood for analysis to establish its concentration. Another variant of determination is the introduction of artificial radioactive isotopes and the standard determination of the number of red blood cells, in which these isotopes are detected and thereby the total amount, so to speak, of the "volume" of blood in the human body.

Summing up, we can say that the amount of blood in the body for each person is individual and to establish more or less accurately its number in the body is quite possible. It is also worth noting that blood loss is always negative, although its replenishment is always possible even in the most difficult situations - the main thing in this case is efficiency, compatibility and medical control at all stages of the procedure.

Video about how many liters of blood in a person

Blood is a liquid tissue, which includes plasma and shaped elements. It performs very important functions in the human body and constantly circulates through the vessels. About how many liters of blood in a person a large number of people wonder. This indicator depends on a variety of factors.

How many liters a person has in biofluids directly depends on a variety of indicators, which include age, weight and gender. An adult contains from 5 to 6 liters of fluid. The composition of the blood includes its liquid part - plasma and suspended shaped elements: red blood cells, platelets and white blood cells. Shaped elements are contained in a ratio of 40 to 45 percent, and plasma - from 50 to 60 percent.

The amount of blood in a middle-aged person is from 4.5 to 5.5 liters. Blood ratios are also determined according to body weight. In a person whose weight is 50 kilograms, an average of 3-4 liters. With a weight of seventy kilograms, the content is from 4.2 to 5.6 liters.

Blood function

That how many liters does a person have blood determined in accordance with its individual characteristics and the functions performed by the liquid. Blood is constantly moving around the system, which includes large and small vessels. They supply fluid to all organs and tissues in the human body.

Red cells deliver oxygen to tissues, as it binds to its molecules. Platelets are participants in the coagulation process during bleeding. With their help, a thrombus is formed at the site of damage. Thanks to leukocytes, protection against the effects of negative external and internal factors is provided.

Blood has a positive effect on kidney function. Also, with its help, oxygen is transported from the lungs to the tissues. Carbon dioxide comes from the tissues into the lungs with the fluid.Thanks to the liquid, an even distribution of hormones, nutrients, biologically active substances and enzymes is ensured. Thanks to the fluid, the final products of metabolic processes are delivered to the excretory system. With its help, water-electrolyte balance is supported, as well as temperature control.

How many liters of blood in the human body

That how much blood contained in the human body, depends on body weight. If it is 50 kg, then on average there are 3-4 liters. With a weight of 60 kg in an adult, it can be 3.6-4.8 liters. If a person weighs 80 kg, then the figure is 4.8-6.4. With a weight of 70 kg, there are 4.3 - 6.4. With a weight of 90 kilograms, the figure will be 5.6-7.2 liters. With a weight of 100 kilograms, there will be 6-8 liters.

In children, indicators may vary slightly. The ratio of the amount of biofluid to body weight in newborns is 15 percent, in children 1 year old - 11 percent, in adolescents - 9 percent.

Safe minimum

Everyone should know how many liters of blood in the human body should be so that this does not threaten his life. Experts believe that if a person loses more than 2 liters of biofluid, then this will lead to death. Such a pathological condition can be diagnosed against the background of a variety of adverse factors. In most cases, hemorrhage is observed with sharp and heavy bleeding. Also, pathology can be diagnosed during surgical interventions and during the recovery period. During treatment of a variety of diseases, patients may be diagnosed with bleeding. A rather frequent cause of it is hemodialysis.

Normally, a person should have at least 3 liters of biofluid. That is why, if he suffers from bleeding, then he needs to provide emergency medical care. In order to save a life with blood loss, a donor transfusion is performed. Donate blood in order to help people donors who have the same group. The safe volume of biofluid is 450 milliliters. Safe plasma intake is 600 milliliters. Surrender of plasma can be carried out no more than twice a month. Donors are allowed to donate biofluids once every 4 weeks. This period is quite enough to restore the qualitative and quantitative blood composition.

Medical institutions that collect donor biofluids have their own database. There are diseases in which a person is strictly forbidden to become a donor. That is why it is recommended that special tests be carried out before taking the biofluid.

How to make up for the loss?

It is necessary to know not only how much blood in a person’s body should be contained, but also about dangerous blood loss. If it is from 20 to 40 percent of the total, then this situation is considered dangerous. With the appearance of blood loss in the body of an adult, it is often diagnosed with malfunctions of the cardiovascular system. In most patients, the respiratory system cannot cope with its work.

With blood loss, a decrease can be diagnosed, as well as the occurrence of dizziness and fainting. Pathology can be determined by pallor of the skin. In this case, the upper and lower limbs become cold. If a person loses 50-70 percent of biofluid, then this becomes the cause of seizures and agony. After this, a fatal outcome is observed. An important aspect is how quickly a person loses blood. For example, if a person loses more than 3 liters of bio-fluid within a short period of time, then death occurs. But, if prolonged blood loss over such a period of time is less dangerous and a person can survive. In the second case, blood loss may be hidden. That is why it is difficult to diagnose and promptly provide an ambulance.

Independently, blood in the body is restored if a person has lost no more than 30 percent. Otherwise, a transfusion is recommended. In order to quickly restore the required volume, the use of food products, which include iron, is recommended. The human diet should consist of beef, liver and red fish. In this case, compliance with the drinking regime is recommended. A person is recommended to drink pomegranate juice in large quantities. You can also drink some red wine. Tea with the addition of milk is quite useful for a pathological condition. Fully blood is independently restored within two weeks.

If the patient has bleeding in the stomach, then a cold compress should be put on him. When bleeding from the nose, the patient should tilt his head slightly forward. Cold is applied to the bridge of the nose. If injuries to the extremities are observed, which are accompanied by bleeding, then this requires applying a tourniquet over them and calling an ambulance.

Not only the composition of the biofluid, but also its volume affects human health. With a significant decrease in the amount of fluid, the development of a variety of pathological conditions can be diagnosed.

Significant blood loss leads to death, which requires its timely completion.