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Gentamicin (Serum) Concentration, 24-Hour Average

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

This test measures the average amount of the antibiotic gentamicin in your blood over a 24-hour period, typically used to guide dosing for infection treatment.

Quick summary

["This test helps ensure your doctor prescribes the right dose of gentamicin to treat infections while minimizing side effects."]

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

Key facts at a glance

LOINC
4271-3
Short code
GnRH Dose
Synonyms
GnRH 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 This Test Is Done

Gentamicin is a powerful antibiotic used to treat serious bacterial infections, such as those caused by staph or other resistant bacteria. Since it can be harmful if taken in too high a dose, your doctor may order this test to monitor how your body processes the medication over time. This helps prevent kidney damage or other side effects.

How the Test Works

Blood is drawn from a vein in your arm. The sample is then analyzed to determine the average concentration of gentamicin in your blood over a full day. The test measures how much of the drug is present in your serum (liquid part of blood).

What to Expect Before the Test

No special preparation is needed for this test. You may have some mild discomfort or bruising at the site where the blood is drawn, but this usually goes away quickly. If you’re on other medications or have certain health conditions, let your doctor know before the test.

Possible Results and Interpretation

Results are used to adjust your medication dose if needed. Your doctor will compare these results to your kidney function and other health factors to determine the safest and most effective dose for you.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Gentamicin 24h

Frequently asked questions

What does a ‘normal’ result mean?
There is no single ‘normal’ range for this test because it depends on your kidney function, weight, and how your body processes the drug. Your doctor will use these results along with other factors to guide your treatment plan.
How often will I need this test?
Your doctor may order this test every few days or weeks, depending on your infection, kidney function, and how you respond to the medication. Follow their instructions carefully.
Can I eat or drink before the test?
You can eat and drink normally before the test unless your doctor specifies otherwise. Blood tests don’t require fasting unless they measure substances like glucose or lipids.
  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