Very often doctors, referring patients to biochemistry, focus on the fact that blood should be donated on an empty stomach. But in some cases they are allowed to drink a little water in the morning, while in others they are strictly forbidden to do so. Will a few sips of liquid affect the deciphering of the analysis, or is this prohibition caused solely by the strictness of the doctor? Let's figure out whether it is possible to drink water before donating blood for biochemistry, or if you still should not do this.

Pros and cons

First of all, the question of whether to donate blood for biochemistry on an empty stomach or not depends on what blood parameters the doctor wants to study. So, even a small amount of water can affect the concentration of white blood cells, uric acid and blood glucose levels. Therefore, people who donate blood for the study of these indicators should not only eat on the day of the examination, but also drink water.

On the other hand, it is recommended to drink a small amount of clean drinking water before taking a vein test to facilitate the blood collection procedure. This is especially true for pregnant women, in whose body a new uteroplacental circle of blood circulation appears, due to which it significantly decreases blood pressure... Therefore, it can be very difficult for a laboratory assistant taking a sample to get into a vein and draw the right amount of blood. And especially impressionable people sometimes faint because of hunger, thirst and the sight of blood. For this reason, as well as to remove thirst, doctors are allowed to drink water in small quantities before the examination. Then the vein is less injured during the blood sampling process, and the laboratory assistant can draw the right amount of blood for the sample.

For example, donors are specifically advised to drink clean water prior to a blood donation procedure.

It should also be noted that the opinions of foreign and domestic doctors on this issue differ significantly. If abroad doctors allow drinking water and even some other drinks on the day when a biochemical blood test is performed, then domestic ones hold a more radical opinion on this matter. And it is forbidden not only to drink water before the analysis, but also to brush your teeth or use chewing gum.

We brush our teeth

Some patients find it too harsh to prohibit brushing their teeth on the morning of the test. But it should be understood that such a prohibition has certain grounds.

For example, not everyone knows that many toothpastes contain triclosan or chlorhexidine, which is synthetic drug antibacterial action. Together with saliva, this drug enters the stomach, and then into the blood, changing its parameters. It should be noted that synthetic antibiotics do not distinguish between harmful and beneficial microflora, therefore they have a destructive effect on all types of bacteria at the same time.

Some pastes also have saccharin added to make them taste better. This substance, entering the bloodstream, affects the glucose level, and distorts the results of decoding.

Well, such a seemingly harmless substance like sodium lauryl sulfate, which is part of many detergents and cleaning agents, turns out to be far from harmless. It is used to create a rich lather that breaks down plaque particles to help clean your teeth. However, it can change the protein composition of cells, and upon reaction with other components of pastes or cosmetics, form nitrate compounds that accumulate in the blood.

And the analogue of this substance - sodium loret sulfate, in addition to nitrates, also forms toxic dioxins.

No matter how carefully you brush your teeth, it will still not be possible to avoid contact of the active substances of the toothpaste with saliva, which means that they will not be absorbed into the blood. Therefore, when prescribing directions for the study of blood parameters that are sensitive to chemicals, doctors focus on the inadmissibility of morning teeth brushing.

For the same reason, chewing gum is not permitted as a breath freshener. Of course, the lack of a morning hygiene procedure causes some discomfort for the patient, however, it should be overcome, taking into account possible risk getting unreliable results.

Summing up

Answering the question whether it is possible to drink water before taking blood, it is important to note that we are talking exclusively about pure water that does not contain sugar, dyes, preservatives, heavy metal salts or other harmful impurities.

Such water can (and should) be drunk by people whose research does not concern the content of sugar, urea, glucose. Otherwise, it is forbidden to eat any food and drink water even in small quantities before the procedure. Any other drinks (tea, juice, coffee) containing sugar, tannins, caffeine, and affecting the analysis result, should not be consumed.

And given the state of domestic equipment and the quality of the reagents used for research, patients should take all possible measures so that any external factors do not affect the results of the analysis. For this reason, you should strictly follow the doctor's recommendations for preparing for the study. And it is necessary to clarify whether it is possible to drink water before taking blood in advance so as not to get false blood counts in the decoding.

Biochemistry is a very accurate study that allows you to identify hidden diseases of many body systems even before manifestation clinical signs disease. And adherence to the rules of preparation for the delivery of the analysis will become the basis for obtaining reliable information about the state of the patient's body.

For most studies, blood is taken strictly on an empty stomach, that is, when at least 8 hours pass between the last meal and blood sampling (preferably at least 12 hours). Juice, tea, coffee must also be excluded.

You can drink water.

1-2 days before the examination, exclude fatty foods, alcohol from the diet. For an hour before taking blood, you must refrain from smoking.

Before donating blood, physical activity must be excluded.
Blood should not be donated immediately after radiation methods of examination (X-ray, ultrasound examination), massage, reflexology or physiotherapy procedures.

Since different laboratories can use different methods studies and units of measurement of indicators, then for the correct assessment and comparison of the results of your laboratory tests, it is recommended to carry them out in the same laboratory.

Before surrender general analysis blood, the last meal should be no earlier than 3 hours before blood sampling.

For determining cholesterol, lipoproteins blood is taken after 12-14 hours of fasting. To determine the level of uric acid, you must follow a diet: refuse to eat foods rich in purines - liver, kidneys, limit meat, fish, coffee, tea in the diet ..

Donating blood for hormonal research carried out on an empty stomach (preferably in the morning; in the absence of such an opportunity - 4-5 hours after the last meal in the afternoon and evening hours).

When examining the level prostate-specific antigen (abbreviated PSA or PSA) abstinence must be strictly observed the day before and on the day of the study. Blood should not be donated for several days after TRUS or palpation prostate(prostate).

The results of hormonal studies in women of reproductive age are influenced by physiological factors associated with the stage menstrual cycle, therefore, when preparing for a test for sex hormones, you should indicate the phase of the cycle.

Reproductive hormones leased by days of the cycle:
LH, FSH - 3-5 days;
Estradiol - 5-7 or 21-23 days of the cycle;
progesterone 21-23 days of the cycle.
prolactin,
DHA sulfate, testosterone - 7-9 days.
Blood for insulin and C-peptide is given strictly on an empty stomach in the morning.
Hormones thyroid gland, insulin, C-peptide surrender regardless of the day of the cycle.

General clinical analysis of urine.

For general analysis, use only the first morning urine sample. The first few milliliters of urine is drained to remove the desquamated cells from the urethra. The toilet of the external genital organs is pre-performed. Urine for examination must be delivered within 2 hours of collection.

Collection of daily urine.

Collect urine within 24 hours with the usual drinking regimen (about 1.5 liters per day). In the morning at 6-8 o'clock, you need to urinate (pour this portion of urine), and then, during the day, collect all the urine in a clean dark glass vessel with a lid, the capacity of which is at least 2 liters. The last portion is taken exactly at the same time when the collection was started the day before (the start and end times of the collection are noted). Store the container of urine in a cool place. At the end of the collection of urine, its volume is measured, the urine is shaken and 50-100 ml is poured into a container in which it will be delivered to the laboratory.

It is necessary to indicate the entire volume of daily urine!

Collection of urine for research according to the Nechiporenko method.

Immediately after sleep (on an empty stomach), the middle portion of the morning urine is collected. Collecting urine is carried out according to the "three-glass" test: the patient begins to urinate in the first glass, continues - in the second, finishes - in the third. The second portion should be predominant in volume, which should be collected in a clean, dry, colorless dish with a wide neck. The collected medium portion of urine (20-25 ml) is delivered to the laboratory

Collection of urine for research according to Zimnitsky.

The patient stays on normal mode food, but takes into account the amount of liquid drunk per day. After emptying Bladder at 6 o'clock in the morning, every 3 hours during the day, urine is collected in separate containers, which are indicated by the collection time or portion number, a total of 8 portions. 1 portion - from 6-00 to 9-00, 2 portion - from 9-00 to 12-00, 3 portion - from 12-00 to 15-00, 4 portion - from 15-00 to 18-00, 5 portion - from 18-00 to 21-00, portion 6 - from 21-00 to 24-00, portion 7 - from 24-00 to 3-00, 8 portion - from 3-00 to 6-00. All collected urine in 8 special containers is delivered to the laboratory.

Collection of urine for microbiological examination (urine culture)

The urine is collected in a sterile container. The collection of morning urine is carried out after a thorough toilet of the external genitalia. THE FIRST 15 ml OF URINE ARE NOT USED FOR ANALYSIS. FOLLOWING 3-10ml. ASSEMBLED IN A STERILE CONTAINER WITH A LID. It is necessary to deliver the container to the laboratory by 8 o'clock.

Biochemical express analysis of feces for dysbiosis.

It is necessary to take 2-4 g (volume of 1-2 teaspoons) of feces into a special container, which must be delivered to the laboratory on the same day. It is necessary to indicate the type of stool (diarrhea, constipation, unremarkable, stool with laxatives).

Research on enterobiasis (to identify teniids and pinworms).

For this study, the biomaterial is taken from the perianal folds (around the anus) by the patient himself. The procedure is carried out in the morning immediately after getting out of bed BEFORE HYGIENIC PROCEDURES, URINARY AND DEFECTION. With a cotton swab, material is taken from the perianal folds in a circular motion (where the above helminths lay their eggs). After the stick is placed in a special container (unused end cotton swab must be deleted). Thus, the material is ready for delivery to the laboratory.

Study of a smear from the throat with determination of sensitivity to antibiotics, diphtheria, mycobacterium tuberculosis, hemolytic streptococcus.

Before the examination, you can not brush your teeth, rinse your mouth with water, drink, eat.

One of the very first diagnostic methods that is assigned to all patients is blood donation. In the course of the study, experts evaluate dozens of indicators, because it is blood that can tell doctors about the presence of hidden diseases, about the possible relapse of the disease and about the effectiveness of the prescribed treatment. Before the analysis, the doctor must explain to each patient how to donate blood from a vein on an empty stomach or not, what other rules must be followed and why it is so important.

Deoxygenated blood

It is an informative test that can tell a lot about the patient's health. Venous blood is used to determine the most important parameters.

Tests that require just venous blood can be divided into several types, namely:

• Analysis of general indicators.
• Analysis of the biochemical composition.
• Glucose test.
• Serological research.
• Hormone test.
• Analysis for tumor markers.
• Test to determine the Rh factor, etc.

All these tests must be taken strictly on an empty stomach in the morning. Why donate blood on an empty stomach, and what other rules for donating blood is important to follow? How food intake can affect test results and is it okay to smoke before taking blood.

Why can't you eat

Blood from a vein on an empty stomach or not? Today you can often find information that this requirement before taking a blood test is already outdated. Some laboratories claim that modern equipment makes it possible to study the biomaterial of a person who has eaten earlier than 8 hours before analysis. However, experts still advise patients to strictly follow this rule, but why?

The fact is that every meal distorts the composition of the blood. When we eat, we get a lot of nutrients that go straight from the intestines into the bloodstream. The biochemical composition of the blood changes at this point and if you have eaten food, the results may be inaccurate. How can food affect a particular test?

Biochemistry. Biochemical analysis- This is the study of blood composition according to 11 main criteria. It allows you to identify many diseases at the earliest stages of development. The study helps to identify diseases of the liver, kidneys, heart, stomach, blood vessels and other important organs and systems. For this reason, the blood for research should not contain excess fat, sugar, trace elements, etc. So, for example, you eat dried fruits before donating blood, they are rich in potassium, doctors will find increased content of this element and diagnose you renal failure, also with other components of any food. After eating, glucose, cholesterol, hemoglobin, etc. may rise. The result is misdiagnosis and wrong treatment.

What else is not allowed

Many patients are interested in whether it is possible to smoke before donating blood, the answer is categorical, no! Smoking contributes to the destruction of blood cells, oxygen starvation and impaired blood flow. If you smoke before the test, your readings will be significantly skewed and doctors may suspect the presence of dangerous diseases... In addition to smoking, be sure to exclude alcohol and even chewing gum.

In addition to restrictions on food and smoking, there are several more rules that must be followed before passing venous blood... First of all, this applies to the reception of any drugs... If you are prescribed a blood test, you need to stop taking medications 3-5 days in advance.

If this cannot be done for various reasons, it is imperative to inform the doctor about it.

It is also necessary to reduce physical activity to a minimum a few days before blood sampling. During intense sports, protein breakdown occurs in the muscles, and some indicators of residual nitrogen increase sharply. These substances are often used to diagnose kidney disease.

What can you drink

Is it possible to drink water before donating blood from a vein, this is another question that worries many patients. Yes, you can drink, but only it should be ordinary boiled water... It is not recommended to drink mineral or carbonated water. The composition of such water can also influence the test result.

However, you need to drink a little. Water does not affect the composition of the blood, but some people are prohibited from drinking large amounts of liquid on an empty stomach. For example, in patients with hypertension, this can cause an increase in blood pressure. Such patients can drink a few sips of water. Sweet drinks are not allowed.

When you can eat

There are a number of tests before which food intake is not prohibited. Can be eaten before genetic blood tests. Human DNA cannot be affected by food.

For this reason, paternity tests, tests for genetic diseases, determination of nationality and other DNA tests can be taken without special preparation.

Sometimes in extreme cases, for example, during an emergency hospitalization, blood is taken from the patient for research, regardless of whether he ate or not. In this case, doctors take into account the urgency of the analysis and take into account only serious deviations of the parameters that cannot be caused by food intake.

Anyone who is scheduled for a blood test is advised to take food with them. For example, you can take a chocolate bar or bun and eat them after taking blood, especially if you still need to undergo additional medical procedures or visit a doctor after that. Also today in almost all medical institutions there is a buffet where you can have a snack after analysis.

To get the most complete picture of your health, to exclude the development of such a serious disease as diabetes and a wide variety of endocrine disorders, it is necessary to periodically check the level of glucose in the body. The exact results of this test are given by a blood sugar test. But before you go to the laboratory, you need to properly prepare. For example, one of the main requirements of doctors is to take an analysis on an empty stomach.

Can I drink water before donating blood, drink alcohol or brush my teeth? These questions concern many of our compatriots, who will have to check the amount of glucose in the blood. laboratory methods... Therefore, we will try to answer them in great detail, to dispel frequently arising doubts.

How to prepare for a blood glucose test

Today in a pharmacy it is not difficult to find a device such as a glucometer, which allows you to determine the sugar level even at home, without going to specialized laboratories. Let's say right away that it is not worth recklessly trusting the readings of the device, since the accuracy of its measurements is extremely low. To achieve the correct result, you must carefully follow all instructions, since, for example, storing the analyzer in an open state can lead to distortion of the received data.

The most accurate results can be obtained in the laboratory, where blood sampling is carried out in the traditional way (from the finger). For this purpose, modern automatic equipment is used, which completely excludes contact of the material with air.

Also, accuracy is affected by correct preparation to analyzes. You must comply with the following doctor's requirements:

• do not drink alcohol 24 hours before donating blood;
• abandon the usual procedure for caring for the oral cavity in the morning before contacting the laboratory. Toothpastes as well chewing gum Alternatively, they contain sugar and a variety of dyes that can greatly distort the picture;
• do not eat anything for about 8-12 hours before analysis.

Failure to meet these requirements leads to an increase in the amount of glucose and makes it impossible to correctly assess your state of health.

As for water, the opinions of doctors here differ greatly. In one laboratory, you may be told that you shouldn't drink anything at all, so as not to nullify the measurement efficiency. In another, on the contrary, recommend to satisfy hunger with plain water (preferably purified or boiled). How to be in such a situation?

If you want to know the exact status information endocrine system and blood glucose, it is best to refrain from drinking any beverages. Especially those that contain sugar in one form or another. Water is no exception. Even if the doctor says you can drink it, try to endure the thirst for several hours. It's for your own good. You don't want a cup of plain water to get in the way of getting accurate data, do you?

What else can affect the distortion of blood test results?

Information about the level of glucose in the blood, obtained as a result of laboratory analysis, can be distorted not only by food intake, alcohol consumption or any drinks. In addition, the results are influenced by:

• excessive mental or exercise stress on the eve of testing;
• the presence of any diseases of the pancreas or endocrine disorders;
• epileptic manifestations;
• carbon monoxide intoxication;
• the use of certain medications.

Why are doctors generally inclined to believe that water can be freely drunk in any quantity? Yes, simply because it has no effect on biochemical composition blood. At the same time, you may encounter a number of other annoying problems. For example, with an increase in pressure, which is inevitable with a large amount of water drunk on an empty stomach. That is why we still recommend refraining from using it until the test.