Tacrolimus trough concentration in whole blood by mass concentration
This test measures the amount of the drug tacrolimus in your blood at its lowest point (trough) to help monitor your dose for immune suppression.
["This test ensures your tacrolimus levels stay within safe ranges to prevent rejection of transplanted organs while minimizing side effects."]
Key facts at a glance
- LOINC
- 77348-1
- Short code
- Tacrolimus Trough Bld-mCnc
- Synonyms
- Tacrolimus Trough Bld-mCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why is this test important?
Tacrolimus is a powerful medication used to prevent organ rejection after a transplant. Your doctor may order this test to check if your dose is working properly and to adjust it if needed. The trough level is taken just before you take your next dose, as this is when the drug is at its lowest concentration in your blood.
What does the test measure?
The test measures the mass concentration of tacrolimus in your whole blood. This helps healthcare providers determine if your dose is therapeutic (effective) or too high/low, which can affect your immune system and overall health.
How is the test performed?
A small blood sample is drawn from a vein, usually in your arm. The blood is then analyzed in a lab to measure the amount of tacrolimus present at its lowest point before the next dose.
What does the result mean?
Results are typically reported in nanograms per milliliter (ng/mL) or micrograms per liter (µg/L). Your doctor will interpret the result based on your specific medical needs, transplant type, and other medications you’re taking. If levels are too high, it may increase the risk of side effects. If too low, your immune system may not be adequately suppressed.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical significance: Tacrolimus trough levels are critical for transplant patients because they balance immune suppression and toxicity. Suboptimal levels can lead to organ rejection (if too low) or toxicity (if too high), such as kidney damage, high blood pressure, or neurological issues. Regular monitoring helps prevent these risks and ensures long-term success of the transplant.
Short name
Tacrolimus trough level
Frequently asked questions
Why do I need this test?
What happens if my tacrolimus level is too high or too low?
How often will I need this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy