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Tobramycin Concentration (Serum or Plasma)

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

This test measures the amount of the antibiotic tobramycin in your blood, helping doctors monitor how well your body is responding to treatment for infections caused by bacteria sensitive to this drug.

Quick summary

["Tobramycin levels help ensure safe dosing and prevent potential side effects."]

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

Key facts at a glance

LOINC
509-0
Short code
Tobramycin Islt KB
Synonyms
Tobramycin Islt KB
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
agar-diffusion
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

Your healthcare provider may order this test if you’re taking tobramycin to treat serious infections, such as pneumonia, bloodstream infections, or infections in the lungs, kidneys, or bones. It’s also used to check if the drug is working properly and to adjust your dose if needed.

What to Expect Before the Test

No special preparation is usually required. You may have a small needle inserted into a vein (venipuncture) to draw blood, or your healthcare provider may collect a sample from an artery if levels need to be checked more quickly.

What the Test Results Mean

Results help your doctor determine whether your tobramycin levels are within a safe range. Too little may mean the infection isn’t fully treated, while too much could lead to side effects like kidney damage or nerve problems.

Possible Side Effects or Risks

While rare, tobramycin can cause side effects like nausea, vomiting, or allergic reactions. Blood tests like this help prevent overuse, which could harm your kidneys or nerves.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Tobramycin is a potent antibiotic used primarily for treating severe bacterial infections resistant to other drugs. Monitoring levels is critical because it’s nephrotoxic (damages kidneys) and ototoxic (damages hearing/balance) at high concentrations. Proper dosing through blood testing helps balance efficacy and safety.

Short name

Tobramycin Level

Frequently asked questions

When might I need this test?
You may need this test if you’re prescribed tobramycin for a serious infection, or if your doctor wants to check how your body is handling the medication.
What does a ‘normal’ result mean?
A ‘normal’ result doesn’t mean the infection is gone—it means your tobramycin levels are likely safe for your body. Your doctor will use these results to adjust your treatment plan.
Can I eat or drink before the test?
You can usually eat and drink normally unless your doctor specifies otherwise. Avoiding food or fluids may be advised for other blood tests, but this one doesn’t require fasting.
  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