Tacrolimus concentration in serum (4-hour post-dose)
This test measures the amount of tacrolimus, a medication used to prevent organ rejection after a transplant, in your blood serum 4 hours after taking your dose. It helps doctors monitor whether your dose is effective and safe.
["This test helps ensure your transplant medication is at the right level for your body."]
Key facts at a glance
- LOINC
- 59822-7
- Short code
- Tacrolimus 4h p SerPl-mCnc
- Synonyms
- Tacrolimus 4h p SerPl-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 medication that helps prevent your immune system from attacking a transplanted organ. Too little can lead to organ rejection, while too much can cause serious side effects. This test is critical for transplant patients to stay on the right dose.
What to Expect Before the Test
No special preparation is needed for this test. You’ll have a small needle inserted into your arm to draw a blood sample. It usually takes a few minutes. You may feel a brief pinch, but it’s over quickly.
What the Test Results Mean
Your doctor will use the results to adjust your medication if needed. If levels are too high, they may reduce your dose. If too low, they may increase it. Always follow your healthcare team’s guidance.
Common Side Effects of Tacrolimus
High levels of tacrolimus can cause side effects like nausea, headaches, or kidney problems. Low levels may mean your organ isn’t being protected well. Your doctor will watch for these signs and adjust your dose accordingly.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is used to monitor long-term compliance and ensure therapeutic drug levels are maintained to balance organ protection and side effects. It’s especially important for transplant patients who rely on this medication daily.
Short name
Tacrolimus Level (4h Post-Dose)
Frequently asked questions
Why do transplant patients need this test regularly?
How often should I expect this test?
Can I eat or drink before 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