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Serum/plasma concentration of nafcillin (antibiotic) by immunoassay

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

This test measures the amount of nafcillin, a type of antibiotic, in your blood. It helps doctors check how much of the drug is working and whether it’s at a safe level in your system.

Quick summary

["This test helps monitor your antibiotic treatment for infections."]

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

Key facts at a glance

LOINC
73251-1
Short code
Nafcillin ind plt IgG SerPl Ql FC
Synonyms
Nafcillin ind plt IgG 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 nafcillin to treat a bacterial infection. It helps ensure the drug is working properly and avoids unnecessary exposure that could cause side effects.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. If you’re on a blood thinner, let your doctor know before the test.

What the Results Mean

Results are compared to a standard range to determine your nafcillin levels. Low levels may mean the drug isn’t working well, while very high levels could indicate problems like kidney issues or improper dosing.

Common Side Effects of Nafcillin

Nafcillin is generally safe but can cause mild side effects like nausea, rash, or diarrhea. Rarely, it may cause allergic reactions or kidney problems. Your doctor will adjust your dose if needed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Monitoring Nafcillin Levels

Frequently asked questions

How often should I expect this test?
Your doctor will schedule follow-up tests based on your treatment plan, infection type, and how your body responds. Typically, tests are done during or shortly after starting treatment, then periodically while you’re on the drug.
What happens if my nafcillin levels are too low?
If levels are too low, your doctor may increase your dose or switch to a different antibiotic. Low levels could mean the infection isn’t fully controlled or your body isn’t absorbing the drug well.
Can I drink alcohol before this test?
No, avoid alcohol before the test as it may affect blood chemistry results and could interfere with how your body processes nafcillin.
  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