Tacrolimus (TAC) / Protopic

Clinical definition of the tacrolimus test
Tacrolimus is an immunosuppressive drug that suppresses the immune system and is used to prevent rejection of transplanted organs by inhibiting the activation of T-lymphocytes. It is given orally or intravenously to those who have had a kidney, liver, heart, or other organ transplant. Tacrolimus levels in the blood are monitored to maintain a therapeutic range. When the concentration is low organ rejection occurs and when the concentration is too high it leads to symptoms associated with toxicity.

Why is the tacrolimus test done?
Tacrolimus test is done to measure the concentration of tacrolimus in the blood. Tacrolimus drug is used after allogeneic organ transplant to lower the risk of organ rejection. Tacrolimus levels are maintained within therapeutic range as high levels of the drug causes kidney damage.

What are the common signs/symptoms when the tacrolimus test is done?

  • Kidney damage
  • Tremors
  • Headache
  • High Blood Pressure
  • Nausea and vomiting
  • Electrolyte disturbances, such as hyperkalemia
  • Tinnitus (intermittent and/or persistent ringing or roaring in the ears)
  • Seizures

Who should do the tacrolimus test (Target population)?
It is done at the beginning of therapy and then at regular intervals to monitor concentration over time.

What should I do before the tacrolimus test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *

Serum (Blood Sample)


Collection of blood from a vein, usually from the arm

No Fasting Required.

No other special preparations required.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my tacrolimus test results?

Time period

Reference Range*

2 to 3 months post transplant

10 to 12 ng/ml

>6 months in selected patients levels

<5 ng/ml

4 to 6 months post transplant

05 to 10 ng/ml

1 month post transplant       

12 to 15 ng/ml

In Liver Transplant Recipients

05 to 20 ng/ml

Diseases/conditions related to the tacrolimus test

  • Atopic Dermatitis (Eczema)
  • Severe Refractory Uveitis (inflammation of the middle layer of the eye) 
  • Vitiligo ( Depigmentation of the skin)
  • Ulcerative Colitis

Other tests related to the tacrolimus test

  • Therapeutic Drug Monitoring
  • Cyclosporine
  • BUN
  • Creatinine
  • Electrolytes
  • Potassium
  • Magnesium
  • Comprehensive Metabolic Panel
  • Glucose

Synonyms : FK506