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Gentamicin in Cerebrospinal Fluid (CSF) by Mass Concentration

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

This test measures the amount of the antibiotic gentamicin found in your cerebrospinal fluid (the fluid surrounding your brain and spinal cord). It helps doctors check how well this drug is working to treat infections like meningitis or brain abscesses caused by bacteria.

Quick summary

["Gentamicin levels in CSF help assess infection treatment effectiveness and monitor for potential side effects."]

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

Key facts at a glance

LOINC
13561-6
Short code
Gentamicin CSF-mCnc
Synonyms
Gentamicin 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 doctor may order this test if you have a suspected bacterial infection in your central nervous system (such as meningitis) and are receiving gentamicin therapy. It helps ensure the drug is reaching the right amount in your CSF to fight the infection while avoiding harmful levels.

What Does the Result Mean?

Results are typically compared to therapeutic ranges specific to your condition and dosage. Low levels may indicate the drug isn’t working well, while dangerously high levels could suggest toxicity. Your doctor will interpret these results in the context of your overall treatment plan.

How Is the Sample Collected?

A small needle is inserted into your spinal column to collect a sample of cerebrospinal fluid. This procedure is called a lumbar puncture or spinal tap. You may feel pressure or a mild ache afterward, but it’s usually not painful.

What Should You Expect Before or After the Test?

Before the test, avoid caffeine or alcohol for 24 hours if instructed, as they can affect fluid composition. Afterward, you may experience mild headaches, dizziness, or a stiff neck, but these are usually temporary. Rest and stay hydrated as recommended by your doctor.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Gentamicin CSF Level

Frequently asked questions

Why is monitoring gentamicin levels in CSF important?
Monitoring helps ensure the antibiotic reaches therapeutic levels to effectively treat bacterial infections while preventing damage to your kidneys or nerves, which can occur with high concentrations of gentamicin.
What happens if my CSF gentamicin level is too low?
If levels are too low, your infection may not be fully treated, and the bacteria could persist. Your doctor may adjust your dosage or consider alternative antibiotics.
Can I drink alcohol before this test?
No, avoid alcohol for 24 hours before the test, as it may interfere with the fluid analysis. Follow your doctor’s specific instructions for any restrictions.
  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