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Fentanyl concentration in serum/plasma

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

This test measures the amount of fentanyl, a powerful opioid pain medication, in your blood. It helps doctors monitor drug levels, especially in patients receiving long-term opioid therapy or undergoing pain management.

Quick summary

["This test helps ensure safe and effective opioid dosing."]

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

Key facts at a glance

LOINC
97249-7
Short code
fentaNYL TissCo Ql Cfm
Synonyms
fentaNYL TissCo Ql Cfm
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
confirm
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 Is Done

Your doctor may order this test if you’re taking fentanyl for pain relief, especially if you’re receiving it through a continuous infusion (like a pump) or if you have a complex pain management plan. It may also be used to check for drug interactions, assess overdose risk, or monitor recovery from surgery or addiction treatment.

How the Test Works

A small blood sample is taken from a vein in your arm. The sample is then analyzed using a sensitive laboratory method to detect and measure the fentanyl present in your bloodstream.

What to Expect Before the Test

There are no special preparations needed for this test. You may have a small bandage on your arm afterward, but you can usually resume normal activities immediately.

What to Expect During the Test

You’ll lie down comfortably while a healthcare professional inserts a needle into your vein. The blood is drawn quickly, and you may feel a brief pinch. The process usually takes less than 5 minutes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Fentanyl Level

Frequently asked questions

How often should I get this test?
The frequency depends on your treatment plan. Your doctor may recommend testing every few days, weeks, or months, depending on how you respond to fentanyl and your overall health. Follow their instructions closely.
What happens if my fentanyl level is too high?
If your fentanyl level is dangerously high, your doctor may adjust your dose, switch to a different opioid, or monitor you more closely for side effects like drowsiness, confusion, or slowed breathing. In rare cases, they might temporarily stop the medication.
Can I drink alcohol before this test?
No, it’s best to avoid alcohol before the test, as it can affect how your body processes opioids and may interfere with test results. Always check with your doctor for specific guidelines.
  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