Test preparation

How to prepare for blood tests

Food intake

• Before taking a blood test, it is recommended to:
• Avoid fatty foods the day before the test
• Refrain from eating for 8–12 hours before the test
• Drink 1–2 glasses of plain still water in the morning 40–60 minutes before the test. This helps reduce blood viscosity, making the blood draw easier

Why is this important?

Eating before a test can distort results and may even make it impossible to perform the analysis.

After nutrients from food are absorbed, the concentration of proteins, fats, carbohydrates and other compounds in the blood increases, enzyme and hormone activity begins and blood viscosity may change.

These factors can affect the concentration of the target substance or alter blood properties in a way that interferes with accurate testing.

Medications

Before taking a blood test:

• Discontinue medication, as agreed with your physician, at least 24 hours before the test
• Avoid dietary supplements containing biotin (vitamin H, vitamin B7):

— if the dose exceeds 5 mg per day – at least 24 hours before the test

— if the dose exceeds 10 mg per day – at least 48 hours before the test

Why is this important?

Any medication or supplement affects the body. Its impact depends on an individual’s physiology and the presence of any medical conditions. Therefore, it is nearly impossible to predict precisely how a particular drug may alter test results.

If you are taking any medications or dietary supplements, please disclose their names to the administrator at the Helix Diagnostic Center when placing your order.

Physical activity and emotional state

Before taking a blood test, it is recommended to:

• Avoid physical activity for at least 30 minutes before the test
• Avoid emotional stress, anxiety or agitation
• Sit down, relax and rest for several minutes before the blood draw

Why is this important?

Physical activity triggers a cascade of enzymatic and hormonal processes. Levels of biologically active substances in the blood increase, organ function intensifies and metabolism changes.

Stress also activates mechanisms that alter internal organ function and start enzyme and hormone regulation. These changes can affect test results.

Alcohol and smoking

Before taking a blood test, you should:

• Refrain from consuming alcohol for 72 hours before the test
• Avoid smoking for at least 30 minutes before the test

Why is this important?

Alcohol affects the nervous system, which regulates all physiological processes in the body. Metabolites of alcohol can impact enzyme systems, cellular respiration and fluid-electrolyte balance. This may lead to changes in concentrations of most biochemical parameters, hormone levels and blood test indicators.

Smoking stimulates the nervous system, increases the concentration of certain hormones and affects vascular tone.

Female physiological condition

To ensure accurate test results, women should:

• Confirm the optimal days of the menstrual cycle (or stage of pregnancy) for testing blood for the following hormones: follicle-stimulating hormone (FSH), luteinizing hormone (LH), progesterone, estradiol androstenedione, 17-hydroxyprogesterone, prolactin and specific markers such as inhibin B and anti-Müllerian hormone
• Indicate the menstrual cycle phase or stage of pregnancy when filling out the referral form

Why is this important?

The concentration of sex hormones and their metabolites in a woman’s body varies significantly throughout the menstrual cycle. Therefore, tests for many hormonal parameters should be performed on specific days of the cycle. The test day is determined by which aspect of hormonal regulation needs to be assessed.

Pregnancy also affects test results. Depending on the week of pregnancy, concentrations of hormones, certain specific proteins in the blood and enzyme activity change.

Time of day

Some tests should be taken strictly at a specific time of day.

Why is this important?

The concentration of many substances in the body changes cyclically throughout the day. For example, the levels of hormones, certain biochemical indicators and specific markers (including those related to bone metabolism).

When monitoring a laboratory parameter, a repeated test should always be taken at the same time of day.

Below are the recommendations for blood collection timing for the determination of various laboratory markers.

Recommended time for blood collection

• Complete blood count

Recommended time for blood collection: 7:00 — 17:00

Acceptable time: 17:00 — 7:00

• Biochemical studies, electrolytes, trace elements

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

• C-peptide, glycated hemoglobin

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

• Coagulogram

Recommended time for blood collection: 7:00 — 17:00

Acceptable time: 17:00 — 7:00

• Vitamins

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

• Bone metabolism markers

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

• Infectious disease markers (antibodies)

Recommended time for blood collection: 7:00 — 17:00; 17:00 — 7:00

• Tumor markers

Recommended time for blood collection: 7:00 — 17:00; 17:00 — 7:00

• Autoimmune antibodies

Recommended time for blood collection: 7:00 — 17:00; 17:00 — 7:00

• Allergens

Recommended time for blood collection: 7:00 — 17:00; 17:00 — 7:00

• Genetic tests

Recommended time for blood collection: 7:00 — 17:00; 17:00 — 7:00

• Hormone tests (except those listed below)

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

• Adrenocorticotropic hormone (ACTH)

Recommended time for blood collection: 8:00 — 10:00

Not recommended time: 12:00 — 17:00; 17:00 — 7:00

• Cortisol (timing depends on the study objective)

Recommended time for blood collection: 7:00 — 8:00

Acceptable time: 18:00 — 20:00

Not recommended time: 12:00 — 17:00

• Aldosterone

Recommended time for blood collection: 7:00 — 8:00

Not recommended time: 12:00 — 17:00; 17:00 — 7:00

• Renin

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

• Parathyroid hormone

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

Prolactin, FSH, LH, estradiol, progesterone, DHEA-S

Recommended time for blood collection: 7:00 — 8:00; 12:00 — 17:00

Not recommended time: 17:00 — 7:00

Thyroid-stimulating hormone, thyroxine, triiodothyronine

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

Testosterone (women)

Recommended time for blood collection: 7:00 — 8:00; 12:00 — 17:00

Not recommended time: 17:00 — 7:00

Testosterone (men)

Recommended time for blood collection: 7:00 — 12:00

Acceptable time: 12:00 — 17:00

Not recommended time: 17:00 — 7:00

Insulin

Recommended time for blood collection: 7:00 — 8:00; 12:00 — 17:00

Not recommended time: 17:00 — 7:00

Why might a blood test need to be repeated?

Distorted or invalid results can be caused by:

Hemolysis – the release of biologically active substances, particularly hemoglobin, into plasma due to the destruction of red blood cells in the blood sample.

Lipemia – an elevated concentration of fats in the blood sample.

Icterus – a high concentration of bilirubin and its derivatives in the blood sample.

In these cases, a repeat blood test is required.

What causes these issues?

Hemolysis is often related to individual physiological characteristics or improper sample collection procedures.

Hemolysis may occur due to:

— prolonged tourniquet application

— traces of a disinfectant (alcohol) left on the skin before venipuncture

— excessive mixing of the blood in the tube

— drawing blood with a syringe and then transferring it into a vacuum tube

— incorrect collection of capillary blood (e.g., pressing too hard near the puncture site or scraping blood from the skin with a tube)

— storing samples at room temperature for too long

Lipemia is commonly caused by consuming large amounts of fatty foods before the test. It can also occur due to metabolic disorders, particularly lipid metabolism disorders.

Icterus may result from prolonged fasting before the test.

How can this be prevented?

To prevent hemolysis: choose venous blood collection. Hemolysis occurs twice as often in capillary samples.

To prevent lipemia: avoid fatty foods the day before your test.

To prevent icterus: fast for 8–12 hours before your test. Do not fast for too long.

How to prepare for urine tests

• Avoid consuming alcohol, spicy or salty foods and foods that may alter urine color (e.g., beets, carrots) for 10–12 hours before testing
• Avoid taking diuretics
• Perform thorough hygiene of the external genitalia before collecting the sample
• Women should collect urine before menstruation or two days after it ends

How to prepare for stool tests

• Avoid taking laxatives, using rectal suppositories or oils, and limit medications affecting intestinal motility (e.g., belladonna, pilocarpine) or stool color (iron, bismuth, barium sulfate) for 72 hours prior to stool collection
• Procure a sterile plastic container with a scoop for stool collection and transport in advance. The container may contain a nutrient medium (peptone) or preservative depending on the test type

Microbiological and PCR tests

• Testing should be done before starting antibiotics or other antibacterial chemotherapy drugs. If this is not possible, wait at least 12 hours after discontinuing the drug

Samples obtained after an enema or after using radiopaque agents (such as barium in case of X-ray examination) are not suitable for testing.

General and antigen tests

• Testing should be done before procedures such as rectosigmoidoscopy or other gastrointestinal diagnostic procedures
• For fecal occult blood testing, avoid eating meat, fish, green vegetables and tomatoes for 72 hours prior to testing

Fecal occult blood test (ColonView)

• Testing should be done before rectosigmoidoscopy or other gastrointestinal diagnostic procedures

Do not collect samples during menstruation, for 3 days before or after it, during hemorrhoidal bleeding, constipation, or when blood is present in the urine.

• Avoid testing while using rectal medications, anticoagulants or high-dose NSAIDs (e.g., aspirin, ibuprofen)

Genetic testing of microbiota

• It is recommended to perform the test 3 months after completing antibiotics, NSAIDs or surgical interventions
• Do not collect the sample during intestinal disorders
• Testing is not recommended during pregnancy, in patients with cancer, diabetes mellitus (consult your physician), or cardiovascular, pulmonary, renal, or liver diseases

How to prepare for urogenital swab tests

Urethral swab (men)

• Avoid local use of antiseptics and/or antibacterial or antifungal medications for 2 weeks before testing
• Refrain from urination and genital washing for 3 hours prior to the test
• Testing should be done no earlier than 2 weeks after completing antibacterial therapy

Urogenital swab (women)

• Testing should be performed before menstruation or 1–2 days after it ends
• Do not douche or use intimate hygiene products before the test
• The swab is collected before a manual examination

For virgins, pregnant women and patients under 18, the sample must be collected by a physician.

How to prepare for enterobiasis test

• Testing should be done in the morning before 10:00 a.m.
• Do not wash the skin around the anus and buttocks before the test

How to prepare for semen analysis

Seminogram

• Abstain from sexual activity for at least 48 hours and no more than 7 days before testing
• Avoid alcohol consumption for 6–7 days before the test
• Avoid any form of intoxication (tobacco, drugs, industrial, medication-related, or toxic substances). If intoxication occurs, testing should be postponed for 5–10 days
• Discontinue medications 24 hours before the test (in consultation with your physician)
• Avoid exposure to high temperatures (saunas, hot baths, fever, or industrial overheating) for 7 days before testing
• Avoid physiotherapy and X-ray examinations for 72 hours before testing
• Avoid heavy physical exertion and stressful situations the day before the test
• To obtain accurate sperm reproduction parameters, the seminogram should be performed twice, with an interval of at least 7 days and no more than 3 weeks
• The abstinence period should be the same for both tests to reduce result variability
• After recovery from febrile colds or other acute illnesses, testing is recommended 7–10 days later
• After treatment for inflammatory urogenital conditions, testing should be done no earlier than 2 weeks later
• After prostate massage, wait at least 3–4 days before testing

Microbiological and PCR tests

• It is recommended to collect samples before starting antibiotics or other antibacterial chemotherapy drugs. If this is not possible, wait at least 12 hours after discontinuing the drug

How to prepare for sputum tests

• A microbiological sputum test should be performed before starting antibacterial therapy or 12–14 days after its completion
• Drink a large amount of fluid (water) 8–12 hours before collecting the sample
• Brush your teeth and rinse your mouth and throat with boiled water immediately before sample collection
• Morning collection is preferred

How to prepare for saliva tests

• Avoid caffeine, alcohol and physical activity for 24 hours before and throughout the saliva collection period
• Do not smoke for 1 hour before saliva collection
• Do not eat for 30 minutes before saliva collection
• Avoid using toothpaste, dental floss, mouthwash or chewing gum 30 minutes before saliva collection
• Rinse your mouth with water 10 minutes before saliva collection
• Remove dentures immediately before saliva collection

How to prepare for cytology sample collection

Cervical and endocervical smears for atypia

• Testing should be done no earlier than day 5 of the menstrual cycle and no later than 5 days before the expected start of menstruation
• Avoid sexual intercourse 24 hours before testing
• Avoid lubricants, tampons, spermicides, douching or intravaginal medications (suppositories, creams) 2 days before the test

Endometrial aspirate

• Testing should be done no earlier than days 6 and 9 of the menstrual cycle and no later than 5 days before the expected start of menstruation
• Avoid douching and intravaginal therapy 24 hours before the test
• All intrauterine procedures should only be performed after complete recovery from any vaginal or cervical mucosal infections. Pregnancy, vaginitis or cervicitis must be ruled out

How to prepare for hair analysis

Tests for narcotics, psychotropic and potent substances, and DNA relationship testing

No special preparation is required

Trace element tests

• Head hairs are recommended. Only if head hair is unavailable, hair from other body areas may be collected
• Stop using therapeutic hair products 2 weeks before hair sample collection

Dyed, bleached or permed hair is not suitable for testing. Wait until enough hair has grown for sampling.

• Hair should be clean and dry. Wash hair no later than 24 hours before sample collection. Do not apply any cosmetic or therapeutic products (creams, oils, gels, etc.) to your hair the day before the test
• Avoid occupational exposure of hair to contaminants (e.g., welding, mining) between washing and sample collection
• Wash and dry your hands and scissors thoroughly before collecting the sample