Preferred Sample Type

Tacrolimus (FK506 or Prograf)

Suitable Specimen Types

EDTA Whole Blood

Tacrolimus (FK506 or Prograf)

Specimen Volume

1 mL whole blood (minimum sample volume 600 uL)

Sample Preparation

Whole blood required. Do not centrifuge

Turnaround Time

24 hours

Sample Processing In Laboratory

In-patient samples received in the lab before 12:00 will be analysed and reported on the same day, whilst samples arriving after 12:00 are reported the next working day. For urgent samples received after 12:00 please phone the laboratory on ext 15980.

Sample Stability

Samples can be stored at room temperature if to be assayed within eight hours, or up to one week at 4 ºC.

General Information

Tacrolimus (FK506) is an immunosuppressive drug that is given orally or intravenously to patients who have had a kidney, liver, heart, or other organ transplant. Normally, a person’s immune system would recognize the new organ as foreign and begin to attack it. Tacrolimus limits this response and helps to prevent organ rejection by reducing the activity of T-lymphocytes. Therefore levels may be measured in order to establish the correct dose, maintain therapeutic levels and detect toxic levels

Generally, the lower the level the better, provided the patient is NOT rejecting. There is a significant clinical component in the interpretation of results.

It is important to monitor levels of tacrolimus for several reasons:

  • There is not a good correlation between the dose of tacrolimus given and level of drug in the blood.
  • Absorption and metabolism of oral doses of tacrolimus can vary greatly between patients and even in the same patient depending on the time of the dose and what, if any food has been eaten.
  • Tacrolimus can cause kidney damage, especially in high doses. Measuring levels in patients who have had a kidney transplant may help to distinguish between kidney rejection (levels are low) and kidney damage due to tacrolimus toxicity (levels are high).
  • Tacrolimus monitoring helps ensure that each individual is receiving the right amount of drug needed to treat his or her particular case.

Patient Preparation

Trough sample required.

Reference Range

Reference or therapeutic ranges are not reported as therapeutic target ranges are applied on an individual basis dependent upon specialty, dosing, period in treatment regime and clinical status. Further advice can be obtained from the appropriate speciality.


  • EQA Status: NEQAS
  • EQAS Scheme: Yes

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