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Tacrolimus concentration in whole blood (4-hour post-dose)

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

This test measures the level of tacrolimus, a medication used to prevent organ rejection after a transplant, in your blood 4 hours after taking your dose. It helps your healthcare team monitor how well your body is responding to the medication.

Quick summary

["This test ensures your tacrolimus dose is optimized for safety and effectiveness."]

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

Key facts at a glance

LOINC
92728-5
Short code
Tacrolimus 4h p Bld-mCnc
Synonyms
Tacrolimus 4h p 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 This Test Matters

Tacrolimus is a potent immunosuppressant, and keeping levels too high can increase infection risk or cause kidney damage, while levels too low may lead to organ rejection. Regular monitoring helps balance these risks.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw a blood sample. The process is quick and usually painless. If you’re on a transplant program, your healthcare team will coordinate this with your medication schedule.

What the Results Mean

Results help your doctor adjust your tacrolimus dose to maintain safe and effective levels. They may recommend changes if levels are consistently too high or too low, depending on your transplant status and overall health.

Common Causes of Abnormal Results

Factors like missed doses, changes in diet (e.g., grapefruit products), illness, or other medications can affect tacrolimus levels. If you notice unexplained symptoms (e.g., fever, unusual fatigue, or organ-related issues), discuss them with your doctor.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Tacrolimus Blood Level (4h)

Frequently asked questions

How often should I get this test?
Your doctor will determine the frequency based on your transplant timeline, medication regimen, and response to treatment. Typically, it may be done weekly or monthly during active monitoring phases.
What if my results are outside the target range?
If your levels are too high, your doctor may reduce your dose or temporarily pause it. If too low, they may increase it. Follow their guidance closely to avoid complications.
Can I drink alcohol before this test?
Alcohol can interfere with some medications, including tacrolimus. Avoid alcohol for at least 24 hours before your blood draw unless your doctor advises otherwise.
  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