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Tacrolimus Test

Last updated July 24, 2019

Approved by: Krish Tangella MD, MBA, FCAP

Chilanga Cement

Tacrolimus is an immunosuppressant drug used to prevent organ transplant rejection.

What are the other Names for this Test? (Equivalent Terms)

  • Advagraf® Blood Test
  • FK-507 Blood Test
  • TAC Blood Test 

What is Tacrolimus Test? (Background Information)

  • Tacrolimus is an immunosuppressant drug used to prevent organ transplant rejection. It is also used to treat conditions that result from excessive immune stimulation, such as eczema. The brand names for tacrolimus include Progaf®, Advagraf®, and Protopic®
  • Tacrolimus works by preventing T-lymphocytes, a type of specialized white blood cell, from producing interleukin-2 (IL-2); IL-2 causes the growth and division of T-lymphocytes. Thus, by preventing its production, tacrolimus suppresses the immune system
  • The immune system is responsible for defending the body against foreign invaders. These include bacteria, viruses, and other organisms. Immune system suppression may be desired after purposely introducing a foreign object into the body for a therapeutic purpose. An example of this is an organ transplant
  • Excessive or inappropriate T-lymphocyte stimulation is also responsible for a variety of diseases. Tacrolimus is sometimes used to suppress the immune system and diminish the harmful effects of abnormal T-lymphocyte stimulation
  • Like every other drug, tacrolimus must be kept within a certain range to prevent unwanted effects. If levels are too high, toxicity may result; if levels are too low, the drug may not be therapeutic
  • A Tacrolimus Test is a blood test to assess the levels of tacrolimus in blood. It is used when adjusting the initial dose, and to ensure that tacrolimus levels stay within an acceptable range 

What are the Clinical Indications for performing the Tacrolimus Test?

The clinical indicators for performing a Tacrolimus Test include monitoring tacrolimus therapy. 

How is the Specimen Collected for Tacrolimus Test?

Following is the specimen collection process for Tacrolimus Test:

Sample required: Blood

Process: Insertion of a needle into an arm vein.

Preparation required: No special preparation is needed prior to the test. 

What is the Significance of the Tacrolimus Test Result?

The significance of Tacrolimus Test is explained:

  • Excessive tacrolimus levels may indicate tacrolimus toxicity, marked by:
    • Seizures
    • Blurred vision
    • Nausea
    • Rapid heart rate 
  • Low tacrolimus levels may indicate more tacrolimus is necessary to achieve a therapeutic dose 

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario. 

Additional and Relevant Useful Information:

  • Tacrolimus is an immunosuppressant drug and may cause various side effects as a result of a weakened immune system. This includes an increased susceptibility to infection
  • A derivative of tacrolimus is used in certain research applications 

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: July 17, 2014
Last updated: July 24, 2019