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Tacrolimus concentration (serum/plasma)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of tacrolimus, a medication used to prevent organ rejection after a transplant, in your blood.

Quick summary

["Your doctor uses this test to check if your dose is working properly and to avoid side effects."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
80550-7
Short code
Tacrolimus DBS-mCnc
Synonyms
Tacrolimus DBS-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Matters

Tacrolimus is a powerful immunosuppressant, meaning it helps your immune system stay calm after a transplant but can also be risky if levels are too high or too low. Your doctor may order this test to monitor your dose and ensure it stays within safe ranges.

How the Test Works

A small blood sample is taken from your arm. The lab uses a sensitive test to measure how much tacrolimus is in your serum or plasma. This helps doctors track your response to the medication over time.

What to Expect Before the Test

No special preparation is needed, but let your doctor know if you’re taking any other medications, especially those that might affect how tacrolimus works in your body.

Possible Results and Next Steps

Results are usually reported in micrograms per milliliter (µg/mL) or nanograms per milliliter (ng/mL). Your doctor will compare these results to your target range and adjust your dose if needed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Tacrolimus Level

Frequently asked questions

What does a high or low result mean?
Too much tacrolimus can cause side effects like nausea, headaches, or even serious problems like kidney damage. Too little may mean your immune system is too active, increasing your risk of infection or rejection.
How often should I get this test?
Your doctor will schedule tests based on your transplant timeline and how your body responds to the medication. Typically, tests are done at regular intervals (e.g., weekly or monthly) to monitor your levels closely.
Can I eat or drink before the test?
You can eat and drink normally before the test unless your doctor advises otherwise. Avoiding food or fluids for a set period isn’t required for this test.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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