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Linezolid Concentration in Plasma (Quantitative)

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

This test measures the amount of the antibiotic linezolid in your blood plasma to check if it’s working properly and to ensure safe dosing.

Quick summary

["This test helps monitor your response to linezolid therapy and prevents potential side effects from too-high or too-low levels."]

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

Key facts at a glance

LOINC
73303-0
Short code
Linezolid ind plt IgM SerPl Ql FC
Synonyms
Linezolid ind plt IgM SerPl Ql FC
Category
hematology
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
flow-cytometry
CPT
82784
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 linezolid, an antibiotic used to treat certain bacterial infections like pneumonia, skin infections, or endocarditis. It helps ensure the medication is at an effective concentration in your bloodstream without causing harmful effects.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw a blood sample. The process usually takes a few minutes, and you can resume normal activities afterward.

What the Test Results Mean

Results are typically reported as a concentration value (e.g., micrograms per milliliter). Your provider will interpret these results in relation to your specific treatment plan and medical condition.

Possible Side Effects of Linezolid

While linezolid is generally safe, high levels in the blood can sometimes cause side effects like nausea, diarrhea, or low red blood cell counts. This test helps avoid these risks by monitoring your drug levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Linezolid Level

Frequently asked questions

How often should I get this test?
The frequency depends on your treatment plan. Your healthcare provider will determine how often to check your linezolid levels, often during or shortly after starting treatment, then as needed for adjustments.
What does a low or high level mean?
Low levels may indicate the antibiotic isn’t working well, while high levels could suggest toxicity. Your provider will discuss these findings with you and adjust your medication if needed.
Can I eat or drink before the test?
Yes, you can eat and drink normally before the test unless your provider gives specific instructions. Avoiding food or fluids may be advised for other blood tests, but this one does not 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