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Tobramycin trough concentration (serum/plasma)

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

This test measures the amount of the antibiotic tobramycin in your blood at a specific time to help your healthcare provider determine the right dose for your treatment.

Quick summary

["This helps ensure the drug stays effective without causing harmful side effects."]

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

Key facts at a glance

LOINC
4059-2
Short code
Tobramycin Trough SerPl-mCnc
Synonyms
Tobramycin Trough SerPl-mCnc
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 tobramycin, a strong antibiotic used to treat serious bacterial infections like pneumonia, cystic fibrosis lung infections, or bloodstream infections. It helps monitor how your body is responding to the medication to prevent resistance or toxicity.

What Does the Result Mean?

The result shows the concentration of tobramycin in your blood at a particular time (usually after a dose). This helps doctors balance effectiveness and safety by adjusting your dose if needed.

How Is the Sample Collected?

A blood sample is taken from a vein, usually in your arm. You may feel a small pinch, but it’s quick and shouldn’t cause significant discomfort.

What Should You Expect Before the Test?

No special preparation is needed unless your doctor instructs otherwise. Avoid eating or drinking for a short time before the draw if specified.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Tobramycin Level (Peak-to-Trough Monitoring)

Frequently asked questions

Why do doctors check trough levels instead of peak levels?
Trough levels assess the lowest concentration of the drug in your blood just before the next dose, ensuring the drug remains effective at preventing bacterial growth without causing harm.
How often will I need this test?
Your doctor will determine the frequency based on your treatment plan, infection type, and response to the medication. It may be done weekly or less often if stable.
Can I stop taking tobramycin if my symptoms improve?
No, always follow your doctor’s instructions. Stopping early may lead to infection recurrence or antibiotic resistance. Your doctor will monitor your levels and symptoms closely.
  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