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Gentamicin trough concentration in serum/plasma

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

This test measures the amount of gentamicin, an antibiotic, in your blood at a specific time to help doctors monitor your dose and avoid potential side effects.

Quick summary

["This test helps ensure your antibiotic dose stays safe and effective."]

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

Key facts at a glance

LOINC
22747-0
Short code
Gentamicin Trough SerPl-sCnc
Synonyms
Gentamicin Trough SerPl-sCnc
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 Is This Test Done?

Doctors may order this test if you’re taking gentamicin, often for serious infections like sepsis or certain types of pneumonia. It helps them check whether your body is properly clearing the drug, preventing toxic levels that can harm your kidneys or nerves.

What Does the Result Mean?

Results are typically reported in micrograms per milliliter (µg/mL). A trough level is taken just before the next dose of gentamicin is due. Too high levels may increase risk of side effects, while too low levels might mean the infection isn’t fully treated.

How Is the Sample Collected?

A blood sample is drawn from a vein in your arm by a healthcare professional. You may feel a small pinch, but it usually doesn’t cause significant discomfort. The sample is sent to a lab for testing.

What Should You Expect Before or After the Test?

No special preparation is needed, but inform your doctor about any other medications you’re taking, as they may affect gentamicin levels. After the draw, you can resume normal activities unless your doctor advises otherwise.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Gentamicin Trough Level

Frequently asked questions

Why do doctors check gentamicin levels at a specific time (the trough)?
Doctors check the trough level because it reflects the lowest concentration of gentamicin in your blood just before the next dose. This helps them determine if the drug is working effectively and at a safe level to avoid side effects.
What are the most common side effects of gentamicin?
Common side effects may include hearing changes (like ringing in the ears), nausea, or changes in kidney function. Rare but serious side effects can include severe kidney damage or nerve damage. Your doctor will monitor you closely if you’re taking this medication.
Can I eat or drink before the blood test?
You can eat and drink normally before the test unless your doctor instructs otherwise. No special preparation is needed, but let your healthcare provider know if you’re taking any other medications that might affect lab results.
  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