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Nafcillin Antigen in Serum/Plasma

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

This test measures the presence of nafcillin, a type of antibiotic, in your blood. It helps monitor how your body is responding to treatment.

Quick summary

["This test helps doctors check if nafcillin is working to treat infections."]

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

Key facts at a glance

LOINC
73250-3
Short code
Nafcillin ind plt IgM SerPl Ql FC
Synonyms
Nafcillin 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

Doctors may order this test if you’re receiving nafcillin therapy to confirm the antibiotic is at an effective level in your blood. It’s particularly useful for tracking infections caused by bacteria sensitive to nafcillin, such as certain types of staphylococcal infections.

What to Expect Before the Test

No special preparation is needed. A blood sample is drawn from a vein, typically in your arm, by a healthcare professional. The test uses serum or plasma, the liquid part of blood without or with clotting factors removed, respectively.

How the Test Works

The test detects nafcillin using an immunoassay method, which identifies the antibiotic by matching it to a specific probe. This method is sensitive and accurate for measuring small amounts of the drug in your blood.

What the Results Mean

Results are qualitative (present or absent) and indicate whether nafcillin is detectable in your blood. High levels may suggest insufficient dosing or poor absorption, while low or absent levels could indicate the drug is no longer effective or you’re not taking it as prescribed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Nafcillin Level (Serum/Plasma)

Frequently asked questions

What could cause abnormal results?
Abnormal results may occur if you’re not taking nafcillin as directed, if your kidneys are not filtering the drug properly, or if you have an infection that is resistant to nafcillin. Always discuss results with your healthcare provider.
How long will it take to get results?
Results are typically available within 24 to 48 hours, depending on your healthcare facility’s lab processes. Your doctor will review the results and adjust your treatment plan if needed.
Can I eat or drink before this test?
You can eat and drink normally before the test, as no fasting is required. However, always follow your healthcare provider’s specific instructions for your test.
  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