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Free morphine concentration in cerebrospinal fluid (CSF)

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

This test measures the amount of morphine (a pain medication) that is not bound to proteins in your cerebrospinal fluid, which helps assess drug levels in the central nervous system.

Quick summary

["This test helps doctors monitor morphine exposure in the brain for pain management or to evaluate opioid use."]

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

Key facts at a glance

LOINC
27054-6
Short code
Morphine Free CSF-mCnc
Synonyms
Morphine Free CSF-mCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order this test if you’re receiving morphine therapy for severe pain, have suspected opioid toxicity, or require monitoring for drug levels in the spinal fluid, such as after spinal anesthesia or for conditions like chronic pain management.

What Does the Result Mean?

Results are not provided with specific reference ranges. High levels may indicate excessive opioid exposure, while very low levels could suggest inadequate dosing or metabolism. Always discuss results with your doctor.

How Is the Sample Collected?

A small amount of cerebrospinal fluid is collected via a procedure called a lumbar puncture (spinal tap). This involves inserting a needle into your lower back to draw fluid from your spinal canal.

What Should You Expect Before the Test?

You may be asked to fast for a few hours before the procedure, avoid caffeine, and stay hydrated. Inform your doctor about any medications, allergies, or recent infections to ensure safety.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CSF Free Morphine

Frequently asked questions

How does this test help doctors manage pain or diagnose opioid-related issues?
This test helps assess whether morphine is reaching the brain effectively, monitor for toxicity (e.g., respiratory depression), or evaluate opioid tolerance in conditions like chronic pain or addiction treatment. It’s particularly useful when standard blood morphine levels aren’t sufficient.
What are the risks or side effects of this test?
Common risks include mild headaches, dizziness, or a small risk of infection or nerve damage at the injection site. Rarely, complications like spinal headaches or nerve damage may occur. Follow-up care may be needed if symptoms arise.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times. Your doctor will discuss them with you during your follow-up visit.
  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