On an empty stomach or not? Instructions on how to take blood tests correctly

Home — Rules for preparing a patient for laboratory and ultrasound examinations — Preparation for blood tests

Food restrictions | Capillary blood | General clinical analysis | Biochemistry | Coagulogram | Hormones | Infections | Glucose tolerance test | TSH | Vitamin D

Blood counts can change significantly throughout the day, so it is recommended to take tests in the morning. For this period, reference intervals for many laboratory parameters have been calculated. This is especially important for hormonal studies.

• All blood tests are done before radiography, ultrasound and physiotherapeutic procedures.
• Do not smoke 2 hours before donating blood.
• For 2-3 days, do not overeat, especially fatty foods, avoid alcohol, intense physical activity, and also do not visit the bathhouse or sauna.

Food restrictions:

• On an empty stomach: at least 4 hours after the last (not large!) meal.
• Strictly on an empty stomach: at least 8 hours after the last meal. In newborns and children in the first months of life, blood sampling is allowed no earlier than 2 hours after eating.
• Fasting: no food intake for at least 12-14 hours.
• Drinking regime . Drinking water does not affect blood counts, so drinking water is allowed (not mineral, non-carbonated). Juice, tea, coffee are prohibited.

Urine tests:

General urine analysis

• On the eve of the test, it is recommended not to eat vegetables and fruits that can change the color of urine (beets, carrots, etc.), and not to take diuretics.
• Before collecting urine, it is necessary to perform a thorough hygienic toilet of the genitals.
• Women are not recommended to take a urine test during menstruation.

Collect your morning urine in a container. To properly conduct the study, during the first morning urination, release a small amount of urine (the first 1 - 2 seconds) into the toilet, and then, without interrupting urination, place a urine collection container into which to collect approximately 50-100 ml of urine. Close the container tightly with the screw cap.

A specialized plastic container is the optimal means of collecting and transporting urine for laboratory research. Ask at pharmacies. The container is a wide-neck graduated translucent glass with a capacity of 125 ml with a hermetically screw-on lid. The container is sterile, does not require pre-treatment and is completely ready for use.

Nechiporenko test

To analyze urine using the Nechiporenko method, the morning portion is collected in the middle of urination (“middle portion”). 15-25 ml is enough.

24-hour urine collection

For laboratory studies, in the morning before collecting urine, it is necessary to toilet the external genitalia.

The first morning urine sample is not collected, but the time of urination is noted. Subsequently, all urine excreted in 24 hours from the marked time of the first urination to the same hour the next day is collected.

The collection of daily urine is optimally carried out in a specialized graduated plastic container of 2.7 liters, which has a wide neck and a textured handle. The container is safe and easy to handle.

You should urinate directly into the container and screw the lid tightly after each urination. Urine should be stored in a closed container in the refrigerator on the bottom shelf, avoiding freezing.

At the end of the collection (the last urination is performed at the same time, which is marked as the time of the first urination, but one day later), the urine can be submitted to the laboratory: the daily volume of urine in a closed container is shaken, after which it is poured into a small container for clinical urine analysis of 125 ml 100 ml portion. You don't need to bring all your urine. At the medical center, report the daily amount of urine.

Collection of daily urine according to Zimnitsky

Urine is collected per day (8 servings in 8 containers, every 3 hours). The first portion of urine in the morning is removed. All subsequent portions of urine excreted during the day, night and the morning portion of the next day are collected in different containers (50 ml) purchased at the pharmacy, each with the time of collection signed.

After collecting urine, accurately measure the contents of the container, be sure to mix it and immediately pour it into a container purchased at the pharmacy. Bring the container to the medical center for examination. You don't need to bring all your urine. At the medical center, report the daily amount of urine.

Urine for sugar

From the daily amount of urine, 50-100 ml of urine or 3 portions of urine collected per day with intervals of 8 hours are delivered to the laboratory:

1 serving - from 8 to 16 hours

2 servings - from 16 to 24 hours

3 servings - from 24 to 8 am (as directed by a doctor).

Urine for PCR studies (tuberculosis, CMV, STIs)

Before collecting urine, it is necessary to toilet the external genitalia. Urine is collected in the morning on an empty stomach after sleep or no earlier than 2-3 hours after the last urination into a sterile plastic container. The minimum volume of urine required for analysis is 20 ml.

Urine for bacteriological research

The urine sample is collected only in a sterile container.

Urine must be collected before starting antibacterial treatment or 3 days after therapy. If the patient is taking antibacterial drugs, then it is necessary to decide on their temporary withdrawal.

After thoroughly toileting the external genitalia, flush the first portion of urine into the toilet, collect the middle portion of 3-5 ml in a sterile hermetically sealed container. Deliver the urine to the laboratory within 1-2 hours; if this is not possible, then the urine sample can be stored in the refrigerator for no more than a day. When transporting the sample, care must be taken to ensure that the stopper does not get wet.

Hormones

Blood collection is carried out strictly on an empty stomach: at least 8 hours must pass from the last meal (preferably at least 12 hours). You are allowed to drink water (non-mineral, non-carbonated). It is forbidden to drink juice, tea, coffee. 2-3 days before the test, do not overeat, especially fatty foods. Avoid alcohol, intense physical activity, and do not visit the sauna or bathhouse.

• On the day of blood collection, avoid taking medications; if withdrawal is not possible, inform the laboratory.
• When studying hormones over time, it is advisable to take blood samples at the same time of day.
• Some hormones need to be taken by women on certain days of the menstrual cycle. This information can be obtained from your doctor.

Attention!Q Blood collection for cortisol is carried out strictly on an empty stomach, strictly in the interval from 8:00 to 11:00 (the exact time of venipuncture is indicated).

PCR studies:

General recommendations for collecting biomaterial for PCR research

1. Various microorganisms have their own characteristics of localization, routes of distribution and excretion, which should be taken into account when choosing the place for taking biomaterial.

2. The collection of biomaterial, if possible, should be carried out during an exacerbation of infection. A few days before the study, you must stop taking chemotherapy. Monitoring the effectiveness of treatment should be carried out no earlier than 3-4 weeks after the end of therapy.

3. The volume of the selected biomaterial should not be excessive, since substances that can cause PCR inhibition or contribute to DNA degradation during storage and transportation get into the sample along with the pathogen. When taking smears and scrapings, it is enough to obtain material in the volume of a “match head”.

4. To take samples, you must use only disposable instruments and sterile plastic containers (or tubes with transport medium) with a tight-fitting lid.

Recommendations for women on preparing for a smear test for PCR, RIF, culture for flora, mycoplasma, trichomonas, fungal infection.

• Such studies cannot be carried out while taking any antibacterial drugs.
• These studies are not carried out during menstruation and for 1-2 days after its end.
• 2-3 days before your visit to the clinic, you should stop using any vaginal tablets, balls, suppositories - both medicinal and contraceptive (Pharmatex, Pantex-Oval, Klion D, Polygynax and others).
• The night before and in the morning on the day of taking a smear, you should not wash yourself or douche.
• IMPORTANT! You cannot take smears for PCR after colposcopic tests.

Urethral material

Before taking the material, the patient is advised to refrain from urinating for 1.5-2 hours. Immediately before taking the material, the external opening of the urethra must be treated with a swab moistened with sterile saline. In the presence of purulent discharge, it is recommended to take a scraping after 15-20 minutes. after urination, if there is no discharge, it is necessary to massage the urethra using a probe to collect material. In women, before inserting a probe into the urethra, it is massaged on the pubic joint. In women, the probe is inserted into the urethra to a depth of 1.0-1.5 cm, in men - to 3-4 cm, and then several careful rotational movements are made. In children, material for research is taken only from the external opening of the urethra. After taking the material, the probe is transferred to the probe packaging, or placed in a test tube with a transport medium and thoroughly washed, the test tube is closed and labeled, after which the material is delivered to the laboratory.

Material from the cervical canal

Before taking the material, it is necessary to remove the mucus with a cotton swab and then treat the cervix with sterile saline solution. The probe is inserted into the cervical canal to a depth of 0.5-1.5 cm, the material is collected with careful rotational movements. If there are erosions of the cervical canal, they must be treated with sterile saline; the material should be taken at the border of healthy and altered tissue. When removing the probe, it is necessary to completely avoid its contact with the walls of the vagina. After taking the material, the probe is transferred to the probe packaging, or placed in a test tube with a transport medium and thoroughly washed, the test tube is closed and labeled, after which the material is delivered to the laboratory.

Vaginal material

The material must be taken before performing a manual examination. Before manipulation, the mirror can be moistened with hot water; the use of antiseptics for treating the mirror is contraindicated. If there is excess mucus or excessive discharge, remove it with a sterile cotton swab. Vaginal discharge is collected with a sterile disposable probe from the posterior inferior fornix or from pathologically altered areas of the mucosa. In girls, the material must be taken from the mucous membrane of the vaginal vestibule, in some cases - from the posterior vaginal fornix through the hymenal rings. After taking the material, the probe is transferred to the probe packaging, or placed in a test tube with a transport medium and thoroughly washed, the test tube is closed and labeled, after which the material is delivered to the laboratory.

Prostate secretion

Before taking prostate secretions, the head of the penis is treated with a sterile cotton swab moistened with saline solution. After preliminary massage of the prostate through the rectum, the doctor performs a pressure massage with several vigorous movements from the base to the tip of the penis. Then 0.5-1 ml of prostatic secretion is squeezed out from the cavernous part, which is collected in a dry sterile container. The material must be delivered to the laboratory within 1-3 hours; transportation must be carried out only in a cooler bag.

Material from the conjunctiva of the eyes

If there is abundant purulent discharge, it is removed with a sterile cotton swab moistened with saline solution. A scraping is taken from the inner surface of the lower eyelid moving towards the inner corner of the palpebral fissure. When taking a scraping, you must hold the eyelid with your hands so that when you blink, the eyelashes do not touch the probe. After taking the material, the probe is transferred to the probe packaging, or the probe is placed in a test tube with a transport medium and washed thoroughly, the test tube is closed, labeled and delivered to the laboratory.

Material from the back of the throat

The material is taken on an empty stomach or no earlier than 2-4 hours after a meal. A disposable probe is inserted behind the soft palate into the nasopharynx and passed along the back wall of the pharynx. If the purpose of the study is the tonsils, the probe is inserted into the lacunae of the tonsils and rotated there. After taking the material, the probe is transferred to the probe packaging, or placed in a test tube with transport medium and washed thoroughly. The tube is capped, labeled and delivered to the laboratory.

Material from the nasopharynx

The material is taken on an empty stomach or no earlier than 2-4 hours after a meal. When taking material, good lighting is necessary, the patient sits against the light source, the root of the tongue is pressed with a spatula, the material is taken with a sterile probe, without touching the tongue, mucous membranes of the cheeks and teeth. After taking the material, the probe is transferred to the probe packaging, or placed in a test tube with a transport medium and washed thoroughly, the test tube is closed, labeled and delivered to the laboratory.

Material from periodontal pockets

Smears from the periodontal pocket are collected in a sterile test tube (Eppendorf type) with saline solution. In this case, the test tubes can be stored in the refrigerator (+4... 6°C) for no more than 12 hours, and they are transported in a cooler bag. You can also take smears with rigid urethral probes. In this case, after taking the material, the probe is placed in its disposable packaging, and in this form it is delivered to the laboratory.

Saliva

12 hours before taking (collecting) saliva, the intake of food, alcohol and medications is excluded. Immediately before collecting saliva, it is necessary to avoid the use of toothpaste and remove dentures. Before collecting saliva, you need to brush your teeth without toothpaste, then rinse your mouth well without using irritants. Saliva is spat out or sucked out from the bottom of the mouth with a disposable syringe and transferred to a test tube (Eppendorf type). Saliva can be stored in the refrigerator (+4...6°C) for no more than 12 hours; transportation is carried out without refrigeration.

Rectal smears for the intestinal group

A sterile disposable probe is inserted into the rectum, the material is collected with rotational movements, the probe is removed and placed in a sterile tube, which is delivered to the laboratory.

Sputum

After thorough oral hygiene (brushing teeth and rinsing with boiled water), the morning portion of sputum is collected in a sterile container. Sputum of a mucous or mucopurulent nature, as well as sputum containing dense whitish inclusions, and sputum colored yellowish, gray or brown, are of diagnostic value. The volume of sputum sufficient for examination is 3-5 ml. To increase the information content, it is possible to repeat (up to 3 times) sputum examination, which increases the number of positive findings.

If sputum is produced irregularly or in scanty quantities, expectorants or irritant inhalations should be used the night before and early in the morning on the day of sputum collection. Preparation of smears from material obtained in this way must be done on the day of collection. In the absence of sputum, the impossibility of aerosol inhalation or its failure to test for mycobacteria, bronchial or gastric lavage water should be examined.

Gastric lavage water

They are studied mainly in young children who cough up sputum poorly and often swallow it. To avoid mixing of swallowed sputum with food, gastric lavage should be taken on an empty stomach. The last meal should be at least 12 hours before taking gastric lavage. Before taking the material to neutralize the stomach contents, the patient drinks 100-150 ml of a solution of baking soda (1 teaspoon per 1 glass of water) in sterile distilled water, after which a sterile gastric tube is inserted into the stomach and the stomach contents are collected in a sterile bottle. The material is immediately delivered to the laboratory and processed, which eliminates the possible destructive effect of gastric enzymes on the pathogen.

Glucose tolerance test

Attention: A glucose tolerance test is prescribed only after consulting a doctor. This study is not performed for patients with type 1 diabetes mellitus.

Blood collection is carried out in the morning, after fasting: at least 12-14 hours must pass from the last meal.

• Before performing the glucose tolerance test, follow a diet for 3 days (no more than 150 grams of carbohydrates per day), exclude intense physical activity, and do not visit the bathhouse or sauna.
• 3 days before the test, stop thiazide diuretics, contraceptives and glucocorticoids (in consultation with your doctor).
• Do not drink water or smoke during the study. Repeated blood sampling is carried out 1 hour and 2 hours after the “load” of glucose.

What does a blood sugar test show?

The analysis shows the level of sugar (glucose) in the blood, which may indicate the presence of diabetes mellitus and other diseases.

Low sugar levels (hypoglycemia) can signal diseases of the pancreas, liver, kidneys and adrenal glands, as well as the hypothalamus.

The most common cause of high blood sugar (hyperglycemia) is diabetes. Hyperglycemia can also indicate other endocrine diseases, problems of the liver and hypothalamus, and a constant inflammatory process in the body.

There is also a glucose tolerance test (also known as a glucose tolerance test or GTT), which is performed to detect prediabetes and is also prescribed to pregnant women.

Preparing for a thyroid-stimulating hormone (TSH) test

TSH levels are the most sensitive test for assessing thyroid function. However, it remains the most frequently deviating from the reference interval among all hormonal studies. To obtain reliable results, in addition to the general rules for preparing for laboratory tests, it is important to follow the rules below:

1. The TSH level changes significantly during the day: its highest concentration is determined in the morning, and its minimum in the evening. You should donate blood at the same time, especially in case of repeated tests, since the time of blood donation plays an important role in the interpretation of the TSH level.
2. In the case of thyroid hormone replacement therapy, it is necessary to take the drug after drawing blood for testing. Taking thyroxine and iodine the day before the test does not affect the TSH concentration. It is advisable to carry out repeated studies of TSH levels in order to monitor therapy no earlier than 6 weeks after changing the dose or type of drug.
3. It must be remembered that the TSH result may be distorted by the effects of medications taken or the products of their metabolism. Before donating blood for analysis, you should consult your doctor about the possibility of limiting the intake of medications during the period of preparation for the study. It is recommended that you stop taking medications, including dietary supplements, before the study. If it is impossible to stop taking medications, you should provide the name of the drug and the time of its last use when donating blood.
4. The thyroid gland is associated with the work of many organ systems, disorders in which can affect the secretion of the hormone: acute and chronic stress, acute infectious diseases, disorders of lipid and vitamin metabolism, leading to excess cholesterol, homocysteine, as well as disturbances in sleep patterns and wakefulness at night, which disrupt the normal rhythm of TSH secretion. The influence of these conditions must be taken into account when interpreting the results if it is not possible to postpone the study to a later date.
5. Different research methods may be used in different laboratories, therefore, in order to correctly evaluate the research results, it is necessary to conduct research in the same laboratory and on the same analytical system.

Before what tests, except for a blood test, should you not brush your teeth?

• Sputum analysis

  - It is recommended to take it on an empty stomach, after rinsing the mouth with boiled water. You cannot brush your teeth with a brush, as you can damage the gums, after which blood can get into the biomaterial, and this leads to inaccurate results.

• Analysis of a throat smear to detect various infections

  - Many toothpastes have antiseptic properties. After brushing your teeth, bacteria may be temporarily removed, so it is likely that the test will show nothing while the body is infected.

• Feces for occult blood

  - when brushing your teeth, you can injure your gums, after which blood will enter the gastrointestinal tract. Moreover, even a small amount of it leads to distortion of the results...

Oral hygiene rules without using toothpaste

People are accustomed to brushing their teeth from an early age, and recently both advertising and newfangled medical TV shows, forums and blogs have been aimed at improving this process.

New electric multifunctional brushes for children and adults are being invented, toothpastes with incredible composition and effect are being advertised.

But one point is missed here - brushing your teeth at night is important.

It is the “overnight” leftover food that harms dental health; the morning procedure is more likely to eliminate psychological discomfort (odor, plaque, etc.).

Therefore, by brushing your teeth thoroughly before going to bed, in the morning (if required by the doctor before donating blood), you can do without toothpaste.

You should know! What can replace morning brushing of teeth:

1. In the evening, on the eve of the morning blood test, you should thoroughly brush not only your teeth, but also your tongue, gums and the inside of your cheeks. It is in these places that a huge number of microbes accumulate.
2. In the morning , you need to brush your teeth and tongue without toothpaste to remove plaque and freshen your mouth.
3. Be sure to rinse your mouth with water or a special solution (10 - 12 drops of hydrogen peroxide per 250 grams of warm water). Rinsing will remove bad breath and neutralize bacteria that appeared at night.

It is prohibited before taking blood tests .

This is explained by the fact that, in addition to sugar, they contain many harmful synthetic compounds, dyes and flavors that can affect the results of the analysis.

Rules for collecting stool

Before submitting the material (3-4 days before), you must stop taking medications (laxatives, castor and petroleum jelly, rectal suppositories). Stool obtained after an enema or barium intake (during X-ray examination) is not allowed for examination.

Before collecting the test, urinate in the toilet. Next, by natural defecation, collect the stool in a bedpan (previously washed and dried). Feces are collected in a clean, disposable container, no more than 1/3 of its volume.

The material must be delivered to the laboratory within 3 hours from the moment the analysis is collected. During this period, it is advisable to store the analysis in the cold (+2...+8C), avoiding freezing.

Conjunctival smears

The material should be obtained with a dry sterile cotton swab on a plastic base under local anesthesia (2 drops of decaine solution). Pulling back the lower eyelid, move the swab 4-5 times along the conjunctiva with rotating movements, grabbing the outer and inner corners of the eye.

After collecting the material, place the swab (the working part of the probe with a cotton swab) into a sterile disposable 2 ml Eppendorf tube with transport medium (TS) (colorless).

Having immersed the working part of the probe in the transport medium, carefully break off the plastic rod at a distance of no more than 0.5 cm from the working part and leave the swab with the material in the transport medium.

Close the test tube tightly with the lid, avoiding any gaps or creasing of the inside of the lid, and label it in accordance with the direction form

Decoding the results

Laboratory specialists interpret the results. They write them on special forms and then give the data to the doctor. The designation of sugar in the form with the result of a blood test is a combination of three letters - GLU.

Normal indicators

Blood glucose levels are presented in the following table:

The table values ​​show the results obtained when donating blood from a finger prick. The result of an analysis using venous blood is influenced by factors such as the gender and age of the person. Therefore, in men the levels can be from 4.2 to 6.4 mmol/l, and in women – 3.9-5.8 mmol/l.

Useful video

From this video you will learn how to brush your teeth correctly and what mistakes you should avoid:

In conclusion, it should be noted that everyone decides for themselves whether or not to brush their teeth before taking a blood test.

It all depends on the degree of responsibility and attitude of the patient towards his health.

But if the doctor “prescribed” such restrictions for the most accurate results, then you should probably listen to them, and it won’t be too difficult to do without such a familiar procedure once.

Taking biochemistry

Biochemical analysis is a kind of “mirror” of the body . The slightest changes in his condition are reflected in the biochemical analysis.

Keep in mind! You should prepare for such an analysis by eliminating all possible causes of false indicators.

In addition to the ban on coffee, sugary drinks, smoking and alcohol , experts recommend not brushing your teeth using toothpaste before the analysis .

Especially when it comes to the study of glucose, urea and sugar.

It is necessary to take into account the quality of reagents that react to any external factors:

• toothpaste contains triclosan and other synthetic substances that have antibacterial properties, which, in turn, can affect the accuracy of the readings;
• saccharin contained in toothpaste directly affects blood glucose levels;
• foaming pastes with the addition of sodium lauryl sulfate affect changes in the protein composition of cells (nitrate compounds can accumulate in the circulatory system).

When prescribing a referral for this test, the doctor does not recommend morning brushing of teeth using toothpaste.

Indications for use

If a patient exhibits symptoms similar to the characteristic features of diabetes mellitus, the doctor prescribes a sugar test. These symptoms include:

• decreased visual acuity;
• decreased level of performance, feeling of frequent fatigue;
• feeling of constant thirst;
• feeling of dryness in the mouth;
• rapid weight loss;
• itching and dry skin;
• frequent urination;

It is also recommended to take the test once a year for people at risk. These include:

• patients who have relatives with diabetes in their family;
• overweight women, men and children;
• women who gave birth to a child weighing more than four kilograms;
• patients taking glucocorticosteroids;
• people with tumor diseases;
• men and women who were diagnosed with heart or vascular disease in middle age.

Pregnancy is also a reason to examine the amount of monosaccharides in the body, since during this period there may be cases of hidden diabetes.