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Gentamicin Concentration (Serum/Plasma)

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

This test measures the amount of gentamicin, a type of antibiotic, in your blood. It helps doctors monitor your dose to avoid side effects while ensuring the medicine works effectively.

Quick summary

["This test helps balance antibiotic safety and effectiveness during treatment."]

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

Key facts at a glance

LOINC
4268-9
Short code
Gentamicin Dose
Synonyms
Gentamicin Dose
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?

Your doctor may order this test if you’re receiving gentamicin therapy, often for serious bacterial infections. It helps track how much of the drug is in your blood to prevent toxic levels that could harm your kidneys or nerves.

How Is the Sample Collected?

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

What Does the Test Result Mean?

Results are typically reported as a concentration value (e.g., micrograms per milliliter). Your doctor will interpret these results in relation to your treatment plan, considering factors like your weight, kidney function, and other medications.

Common Uses and Considerations

Gentamicin is used to treat infections caused by bacteria that are resistant to other antibiotics. Regular monitoring helps prevent overuse, which can lead to kidney damage or hearing loss, or underuse, which may not fully treat the infection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Gentamicin Level

Frequently asked questions

Why might my doctor want to check my gentamicin level frequently?
Your doctor may check your gentamicin level often, especially in the first few days of treatment, because this antibiotic can build up in your body quickly. Frequent monitoring helps prevent dangerous levels that could harm your kidneys or nerves.
What happens if my gentamicin level is too high?
If your gentamicin level is too high, your doctor may adjust your treatment plan. This could mean reducing your dose, changing the frequency of your doses, or switching to a different antibiotic. High levels can cause side effects like nausea, hearing loss, or kidney problems.
Can I eat or drink anything before this test?
You can usually eat and drink normally before this test unless your doctor gives specific instructions. However, if you’re on a special diet or have kidney issues, follow your doctor’s advice to avoid interfering with the test 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