Notes when taking blood samples for bio-tests

Article written by Dr. Tran Thi Huyen Trang – Laboratory Doctor, Laboratory Department – Share99 Times City International Health Hub

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Deficiencies in the technique of obtaining the product can lead to errors of the test results. For accurate test results it is necessary to pay attention to a number of problems when taking the product.

1. When to get blood

  • For biomedification tests, it is recommended to take blood samples in the morning after fasting overnight 12 hours (especially with triglycerid, cholesterol, fe tests that force fasting for at least 12 hours). In case of necessity, the time of blood donation may depend on the doctor's prescribed treatment.
  • Due to changes in circadian rhythm, the concentration of certain substances may vary depending on the time of blood sampling, especially some tests such as ACTH, Cortisol, Renin need to take blood before 10am.
  • For drug dosing tests such as Tacrolimus, Everolimus, Amikacin, Vancomycin, Methotrexate should comply with the correct blood taking time, usually the time of T0 (just before taking the next dose of the drug).
  • Discontinue all forms of practice 24-48 hours before blood collection.

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The moment of blood sampling affects the blood index

2. Blood test location

Blood tests can be taken in veins, capillaries and some special tests that require arterial blood (e.g., blood gases). There are certain substances that may have altered due to changes in metabolism or due to the different distribution between the two areas of the body. For example, oxygen levels, glucose levels in arterial blood are higher than intravenous blood; Capillary blood protein levels are higher than intravenous blood.

3. Some other considerations when sampling for biomedization tests

  • Fastening time: It is necessary to take off the garage immediately after the needle has entered the vein due to anaerobic metabolism that increases glucose decomposition, reduces blood pH, accumulates lactate. Hypoxia leads to the release of potassium from cells…
  • Patient's position when taking blood: The patient needs to be rested for 10 minutes before taking blood. Different positioning of the patient when taking blood (lying or standing) can also alter the concentration of certain substances in the blood. The change in the concentration of certain substances in the blood when changing the patient's position from lying to sitting: Urea decreased by 3%, Potassium increased by 3%, Calcium increased by 4%, Creatinine increased by 5%, Protein increased by 10%, AST increased by 15%, ALT increased by 15%, especially Cholesterol increased by 18%.
  • Selection of test tubes

Depending on the type of test, choose different types of tubes such as: Non-anti-freezing or anti-freezing pipes: EDTA- K3 or K2, Sodium Citrate 3.2%, Heparin, NaF.. . After blood is taken, cover the tube and reverse gently 5-10 times depending on the type of test tube. With non-anti-freezing tube: do not shake the tube

  • The order of blood sampling into the tubes is as follows:
      1. Blood cultures
      2. Blood clot tube (anti-freezing with Sodium Citrate)
      3. Non-freezing tubes (gel or non-gel)
      4. Heparin anti-freezing tubes (gel or non-gel)
      5. EDTA Anti-Freezing Tube
      6. NaF Pipe
      7. Other tubes (e.g., blood s deposited…)

Blood duc tube

Types of test tubes in clinical testing

Sample sending time: With the majority of tests, send the sample within 1 hour after taking and storage at room temperature. The permitted storage time for serum or plasma is 4 hours at room temperature, 24 hours at 4oC. For some tests, the time for submitting samples of some special tests is as follows:

  • Lactic acid (lactate), Ammonia(NH3) Sampled with NaF (Sodium Fluorid – Potassium oxalate), then the blood lactate stabilized for about 8 hours.
  • Blood glucose: If blood is taken into the heparin anti-heparin tube, it must be centrifugal and plasma separated within 1 hour after blood is taken. If plasma cannot be separated early, blood should be taken into the tube containing anti-freezing substance Sodium Fluoride – Potassium oxalate, then glucose stabilizes 24 hours at room temperature.
  • Concentration of the drug Tacrolimus, everolimus: immediately sent to the laboratory after blood is taken. If the sending time is delayed, it must be preserved at a temperature of about 2-4oC (foam containers containing ice can be used).
  • ACTH and Renin activity: before sampling, store the EDTA tube in the refrigerator first to cool the sampling tube. After sampling, immediately send it to the laboratory department.

Hemolymic blood samples must be removed: Hemolysis caused by blood loss will increase components such as potassium, phosphate, SGOT, SGPT … in plasma and increase hemoglobin. Hemoglobin may cause interference in some testing methods.


Bio-testing should be performed at a reputable medical facility

Also Creatinine test results may be affected when blood samples have high levels of Bilirubin.

Infusion: Always have to take blood in another hand with the hand that is transmitted glucose. Blood glucose levels can be very high if blood is taken in the same hand that is being transmitted glucose.

Share99 International Health Hub is one of the hospitals that not only ensures professional quality with a team of leading doctors, modern technology equipment system but also stands out for comprehensive and professional medical examination, consultation and treatment services; civilized, polite, safe and sterilized medical examination and treatment space. Customers who choose to perform tests here can be assured of the accuracy of the test results.

Customers can directly go to Share99 Health System nationwide for examination or contact the hotline here for assistance.


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About: Minh Quynh

b1ffdb54307529964874ff53a5c5de33?s=90&d=identicon&r=gI am the author of I had been working in Vinmec International General Hospital for over 10 years. I dedicate my passion on every post in this site.


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