Why is a general blood test taken from a vein. How to take blood from a vein

The doctor receives information about the patient's health different ways. Usually, the appointment begins with a survey, followed by an examination and appointment of tests. For an accurate diagnosis, blood is needed: its studies reveal pathological changes in the body.

Collection of blood from a vein

What is the purpose of a blood test?

• General analysis. It is prescribed during a preventive examination, for the diagnosis of infections, inflammations and pathologies. Shows cellular composition blood.
• Biochemical data indicate possible pathologies liver, kidney, oncology. Conclusions are drawn on the basis of indicators of chemicals - proteins, lipids, enzymes, etc.
• Immunology is needed to identify potential allergens. Detects cellular and humoral immunity.
• Hormonal - shows the level of the main hormones and their ratio. Needed to control thyroid function and metabolism.

The technique of blood sampling is important not only for patient comfort, but also for an adequate diagnosis. It is important to exclude contact of the biomaterial with air, the hands of medical staff and devices. Most modern laboratories use vacuum systems. They are safe, convenient, and make blood sampling less painful.

How should a patient prepare for a blood test?

If you are recommended to donate blood, it is important to properly prepare for the procedure. The procedure is not always performed on an empty stomach, this point should be clarified with the doctor. It is believed that the interval between food intake and biomaterial sampling should be at least 4 hours.

General rules for preparing for venipuncture:

• Most of these procedures are performed in the morning on an empty stomach. If you are using an independent laboratory, please ask for preferred hours and conditions.
• It is advisable not to overeat the day before, not to abuse spicy, fatty and heavy foods. This can distort the overall picture, especially biochemistry.
• Eliminate alcohol at least a day before the analysis.
• Do not smoke 1-1.5 hours before the procedure.
• If you have been assigned other studies, such as x-rays or fluorography, then they must be rescheduled for a later time. The same goes for physiotherapy.
• In some cases, it is necessary to cancel the medication.
• Try to calm down and avoid stressful situations, especially if you are tested for hormones.

Compliance with these rules will increase the accuracy of the result.

A general blood test is prescribed in order to see which substances in the body are lacking and which are in excess. The content of certain indicators varies depending on gender, age and the presence of chronic diseases. The results of the analysis are entered into a special form that facilitates decoding and structures the data obtained.

Blood from a vein

What will the general analysis show

Attention! Blood donated from a vein, depending on the doctor's request, can show from 8 to 31 points.

This includes counting the total number of red blood cells and platelets, white blood cells and a number of other indicators. Some of them determine not the quantitative ratio, but the shape of the cells, their volume or other characteristics. It is also often prescribed to determine the erythrocyte sedimentation rate and calculate the leukocyte formula. To determine it, it is determined in what percentage ratio certain leukocytes are in the blood.

Hemoglobin and hemocrit

The level of hemoglobin contained in the blood is also determined - this is with regard to the total amounts in the biomaterial.

Also, averages are often calculated - the average concentration in the blood of hemoglobin contained in erythrocytes or in one erythrocyte. Calculated cells are produced by the bone marrow and stay there until they are needed in the body, then they are sent to the bloodstream, and the bone marrow begins additional production of such cells.

Hematocrit is an indicator that reflects the rate of thinning or thickening of the blood.

The amount of this substance in the blood is very important to maintain at a level so that uncontrolled thrombosis or bleeding does not occur. It looks like the ratio of its elements to the amount of plasma.

vacuum test tube

What will leukocytes show

Leukocytes, or white blood cells, are one of the main indicators of blood. They are fighting infection. For these purposes, they are endowed with the ability to determine which of the cells are alien and which substances in them are pathogenic. If there is a large infectious inflammation in the blood, their number will be increased several times, as leukocytes are engaged in the fight. Too little of them in the blood is also bad.

A low level of white blood cells indicates that the body is highly susceptible to any disease and is not able to fight those that enter the bloodstream. pathogenic bacteria. With a very low white blood cell count, the human immune system usually practically does not work. This means that any cold can be fatal. Also, often a critically low number of leukocytes indicates the presence of a cancerous tumor.

Taking a part of the blood for analysis

There are five types of white blood cells, and each type is responsible for a different function.

Lymphocytes, the content of which in the blood is about 35%, remain in normal condition immunity and monitor all immune system person. 5% are engaged in the destruction and absorption of disease-causing or simply foreign cells in the blood. Basophils help to detect such cells. Basophils are usually not more than 1% in the blood. Neutrophils destroy all foreign bacteria and bacterial infections, their rate in the biomaterial is usually 55%. And, the norm of which is 2.5%, fight allergens and carrier cells.

What will the erythrocytes show

Erythrocytes are red blood cells in the biomaterial. Appearance such cells look like a donut, thin in the center and without a hole. Red blood cells contain hemoglobin, which helps carry iron and oxygen to the cells. Hemoglobin carries carbon dioxide from the cells to the lungs. The total blood count can determine not only the total number of red blood cells, but also the amount of hemoglobin in them, the shape of the cells and their size. In normal condition and human health, they all have the same shape and size.

General analysis from a vein

The content of 4.5-5 million will be normal. A reduced number of red blood cells indicates the presence of anemia in the patient, which manifests itself as a general weakness of the body, fatigue and the presence of shortness of breath. An increased number of these cells is much less common and indicates the presence of a disease such as erythrocytosis. With an increased content of red blood cells, severe poisoning with pronounced symptoms is usually observed. The patient has vomiting and diarrhea, general weakness and severe fluid deficiency.

Important! If you take general analysis blood after a serious illness or in intense heat, this will also affect the results.

The number of leukocytes will be greatly reduced, and erythrocytes, on the contrary, will be markedly increased. The same can be observed if you go to donate blood on the eighth floor without an elevator. The results usually reflect separately the number of red blood cells, separately - the amount of hemoglobin in the blood. In the event of a lack of these substances, red blood cells will indicate the presence of anemia, and hemoglobin - its severity.

How to donate blood

Special preparation for the surrender is not required - you just need to come and give a hand to a specialist. However, there are a few things to consider before submitting. On the day of the test, you should not eat food, this can directly affect the results. At least 8 hours should elapse between the moment of delivery of the biomaterial and the last meal, unless otherwise recommended by the doctor. The last meal before donating blood should refrain from drinking alcoholic beverages, as this dramatically increases the number of leukocytes in the blood and critically reduces the amount of hemoglobin, not counting others chemical reactions in the body. As a result of such an incorrect delivery, a person will receive incorrect test results, and the specialist will prescribe unnecessary drugs to maintain a false state of a person.

What is determined by the general analysis

Important! Also, on the last day before the delivery of the biomaterial, one should not lean on fried, spicy and heavy foods, as this may affect the results.

You should not start to drastically change the diet and diet exactly the day before the delivery, as this will be stressful for the body. On the day of the test, you need to appear on an empty stomach in medical institution before 11 am, otherwise the results will be incorrect.

On the day of delivery, you can not drink coffee, tea, and even more so, sweet carbonated drinks, fruit drinks and compotes. The maximum that you can drink is pure unsweetened still water, which should not be carried away either. Heavy physical exercise on the eve or on the day of delivery are not recommended, if possible, then this day should be spent in silence at home.

Deciphering the results

If x-rays, ultrasound or physiotherapy are scheduled for the same day, then you first need to donate blood until the body has received a large medical load and radiation. An hour before blood donation, it is strictly forbidden to smoke, and even more so, take alcoholic or toxic drugs and drinks. Do not rub or knead the hand from which the blood will be taken, as this may cause elevated level leukocytes in the blood. Before donating blood, it is recommended to sit quietly in front of the laboratory for ten to twenty minutes, restore internal balance and in no case worry about the results.

Attention! Only a doctor can decipher the received data, taking into account all the characteristics of a person.

He pays attention not only to the numbers on paper. The calculation also takes into account the weight, height, sex and age of the patient, the characteristics of his body, transferred and chronic diseases. It also takes into account all the results of the tests that the patient passed earlier.

Today, a blood test is taken from a vein in almost every patient admitted to a hospital with a particular disease, and even from simply turning to a local therapist.

This is explained by the fact that it is the blood that first reacts to all changes occurring in the human body.

So, the composition of the biofluid is significantly affected by the banal acute respiratory disease, not to mention more serious diseases.

What are the types of blood tests from a vein? This is a general blood test from a vein and a biochemical one. What each of these options shows is discussed in more detail in the article.

Despite the fact that a clinical or general blood test is traditionally taken from a finger, all large quantity modern clinics, especially if the most complete, detailed clinical analysis is needed, he prefers to take blood from a vein.

This is explained by the fact that a detailed clinical analysis involves the use of a significant amount of biofluid, which can be quite problematic to obtain from a finger, but very simple - from a vein.

A detailed clinical blood test is prepared on ultra-modern expensive analyzers that require quite a large number material for research.

And another argument in favor of taking blood from a vein, and not from a finger, is that capillary and venous blood are quite different in composition.

The latter, for example, has much more glucose, which can be very important for making a diagnosis in some diseases.

Thus, if it is a detailed analysis that is needed, preferably venous rather than capillary blood.

What is research? What is the difference between clinical detailed and ordinary analyzes?

A complete blood count is a study of a person’s biofluid, aimed at identifying pathological processes in his body on early stages their development.

The analysis is carried out both for therapeutic and prophylactic purposes, as well as to monitor the course of pregnancy.

Clinical analysis of the biofluid provides information on various blood parameters.

Their number can range from 10 to 50. If the number of obtained parameters exceeds 30, this is a detailed general analysis.

It is preferable to take a clinical analysis (even from a finger, even from a vein), preferably on an empty stomach, having previously given up too heavy (spicy, fatty, fried) food 2 days in advance.

Biofluid sampling on an empty stomach is explained by the fact that if the patient eats less than 6 hours before the study (even if he just drinks sweet tea with cookies), this can greatly distort the results of the analysis.

If there is nothing long time too difficult, it is still advisable to come to the laboratory on an empty stomach and remain hungry when donating blood, but take a brake with you so that you can have a bite to eat immediately after the procedure.

Deciphering the results

What parameters does the study show? Deciphering the data obtained and making a diagnosis based on them is the business of a qualified specialist.

Along with this, knowing the basic parameters, you can try to deal with the results yourself.

The article provides information on the most important indicators, without knowing which, it makes no sense to try to decipher the results:

• The iron-containing protein hemoglobin. Norm: 120-160 g/l. Low hemoglobin indicates anemia, severe blood loss;
• Hematocrit is the ratio of certain cells to total blood. Norm: 36 - 45%. Hematocrit drops sharply in case of intense blood loss, during acute infectious diseases, some autoimmune diseases;
• ESR (erythrocyte sedimentation rate). Norm: 1 - 12 mm per hour. An increase in ESR indicates strong inflammatory processes in the body, oncological diseases, blood diseases;
• Erythrocytes (red blood cells). Norm: 3.9x10 12 - 5.5x10 12 cells / liter. A decrease in the number of red blood cells indicates the development of anemia in a patient. A significant excess of the norm can signal the development of a disease such as leukemia. A decrease in the level of red blood cells is possible due to diseases such as myeloma, cancer, bone marrow metastases, measles;
• Leukocytes (white blood cells, their types: neutrophils, eosinophils, basophils, monocytes, directly, leukocytes). Norm: 4 - 9x10 9 / liter. If the number of leukocytes is higher than normal, then an inflammatory process is guaranteed to develop in the body;
• Lymphocytes (defenders of immunity, the main types of lymphocytes: T-lymphocytes, B-lymphocytes, NK-lymphocytes). Norm: 1 - 4.8x10 9 / liter. If the lymphocytes in a person's blood are significantly higher than normal, he may develop a viral disease or acute radiation sickness. The lack of lymphocytes indicates oncological diseases, an immunodeficiency state;
• platelets. Norm: 170 - 320x10 9 / liter. Elevated platelet counts are seen in diseases of cardio-vascular system such as thrombosis. So, with thrombosis (especially at its initial stage, during the formation of a thrombus), there is an accumulation of platelets in some difficult places in the vessels. Along with this, with thrombosis, other indicators in the clinical analysis will be deviated from the norm.

A detailed blood test also necessarily includes a leukocyte formula, which indicates how all types of leukocytes in the blood correlate and whether there are any deviations from the norm in this ratio.

Biochemistry as a study

A biochemical blood test, unlike a clinical one, must be taken strictly on an empty stomach, since this analysis demonstrates indicators such as total protein, sugar, cholesterol, which are guaranteed to change if the patient has a meal less than 8 hours before the study.

In addition to taking a biofluid sample on an empty stomach, doctors recommend excluding junk food from the diet 2-3 days before blood sampling (first of all, fast food, fried, fatty, spicy, canned food), and also try to prevent physical and emotional overload.

A biochemical blood test on an empty stomach should be taken even by pregnant women and infants. In the latter case, the infant should not be breastfed for less than 4-5 hours prior to the examination.

What does biochemical analysis show? A biochemical blood test allows you to find out if the balance of all blood elements is observed, whether there are inflammatory processes and diseases of various nature.

Decryption must include the following parameters:

• total protein. Norm: 64 - 84 g / l. An increased protein indicates infectious or oncological diseases, a lower protein indicates diseases of the liver and kidneys;
• Hemoglobin. Norm: 120 - 160 g / l. Low hemoglobin indicates anemia, severe blood loss;
• Haptoglobin. Norm: adults - 150 - 2000 mg / l. A low level of haptoglobin may indicate autoimmune diseases, and a high level may indicate malignant neoplasms;
• Glucose. An indicator such as glucose or sugar can go in the general list of analysis parameters, or it can be given separately, like a biochemical blood test for sugar;
• Normally, sugar should be 3.3 - 5.5 mmol / l. If the sugar is higher than this norm, this indicates the possible development of diabetes or impaired glucose tolerance. Along with this, sugar can rise if the patient is taking corticosteroids and diuretics, if he is diagnosed with epilepsy, or if carbon monoxide poisoning occurs. If the sugar is significantly below normal, then this could be due to illness. gastrointestinal tract and pancreas, slow metabolism, sarcoidosis;
• Urea. Norm: 2.5 - 8.3 mmol / l. Growth this indicator indicates kidney disease and urinary tract, heart failure;
• Cholesterol. Norm: 3.5 - 6.5 mmol / l. High cholesterol may indicate the development of atherosclerosis, heart disease;
• Bilirubin. Norm: 5 - 20 µmol / l. If bilirubin is significantly higher than normal, the person is sick viral hepatitis. An increase in bilirubin may also indicate cirrhosis of the liver and gallbladder disease.

Biochemical analysis also provides information on cellular enzymes: alanine aminotransferase, aspartate aminotransferase, lipase and amylase.

If these indicators are deviated from the norm, this may indicate various diseases gastrointestinal tract.

In some situations, for example, if the patient did not donate blood on an empty stomach, and the decoding of the analysis showed inaccurate data, the analysis of blood from a vein is taken again.

A second sample of biofluid is also taken for examination if the blood has coagulated immediately after its collection.

The latter is not evidence of any pathology in the patient, but often occurs as a result of elementary laboratory assistant errors.

So, if the blood in the test tube has clotted, this means that the medical worker did not add a special preservative to the vessel, or the material was stored at too high a temperature.

How many times can I take a venous blood test? As much as the attending physician prescribes - there are no special restrictions here, as well as contraindications for taking the test.

Both biochemical and clinical blood tests are prepared, as a rule, for several days - in state medical institutions, within one day - in private laboratories.

Most of the pathologies for which people are forced to see a doctor need additional analyzes. One of the most common is taking blood from a vein for research. This analysis allows you to determine many indicators that help in establishing a diagnosis or correcting treatment.

But it is important to correctly donate blood from a vein for analysis. This is not such a simple procedure as the study of capillary blood from a finger. A laboratory assistant can handle it or even learn the person himself on his own when it comes to patients with diabetes mellitus.

The study of venous blood requires qualification:

• nurse;
• paramedic;
• Doctor.

Preparation for the procedure

Responsible attitude to the moment of donating venous blood means properly preparing for the analysis. If any rules are not followed, the results of the study will be incorrect. This will affect the correct diagnosis and treatment.

Without treatment, thrombophlebitis will spread upward through the vein, causing an increasingly extensive lesion. Phlegmon may develop - inflammation of the soft tissues. Phlegmon appears when an infection from a vein passes to the muscles and fatty tissue surrounding it. It's dangerous infectious complication which requires immediate assistance.

Phlegmon and thrombophlebitis are fraught with the development of sepsis - blood poisoning. This is a common infection when bacteria actively multiply in the bloodstream. Sepsis quickly leads to failure of the liver, kidneys, lungs. Without timely treatment, sepsis leads to death.

Video - blood sampling from a vein

For a general (clinical) blood test, capillary blood is also suitable. Capillary blood is taken, it is examined under a microscope, venous blood is placed in a special analyzer apparatus. If blood is taken from a vein, along with a general analysis, you can perform a biochemical study, a study, hormones, and identify sexually transmitted pathogens (gonococci, etc.). Many diseases affect the composition of the blood, so this analysis is an objective way to diagnose a health condition.

A biochemical blood test is performed to diagnose pathologies of the kidneys and liver and kidneys, disorders of the gastrointestinal tract, acute and chronic infectious, viral diseases etc.

A general blood test is performed by the number of its constituent components (leukocytes, erythrocytes, platelets, hemoglobin). Each of these components has its own rate of content in the blood. Any deviations will indicate developing disease.

How to take blood from a vein

Before the analysis, you need to give up alcohol, fatty and fried foods two days before the test, refrain from smoking 1 hour before the test, and exclude physical activity and stress half an hour before. A biochemical blood test is needed on an empty stomach, after an 8-hour fast. General - not earlier than three hours after a light snack.

An increase in the ESR level indicates inflammation or other pathology.

Blood from a vein is taken as follows. The patient or lies down in comfortable position, his arm at the elbow should be unbent. A special pillow is placed under the elbow, after which the medical worker puts a tourniquet on the patient's arm. The patient must clench and unclench his fist several times to fill the vein with blood. Then the skin is treated with alcohol. The puncture is made with a syringe. When the needle enters the vein, it removes the tourniquet and takes a certain amount of blood, then removes the syringe needle.