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Erythromycin Immunoassay (Plasma/Serum)

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

This test measures the amount of erythromycin, an antibiotic, in your blood. It helps assess how your body is responding to treatment.

Quick summary

["Check your erythromycin levels to ensure proper dosing and avoid potential side effects."]

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

Key facts at a glance

LOINC
73394-9
Short code
Erythromycin ind plt IgM SerPl Ql FC
Synonyms
Erythromycin 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 erythromycin (or another macrolide antibiotic) and want to monitor its levels in your blood. It can also be used to check for resistance or to adjust treatment if needed.

What to Expect Before the Test

No special preparation is usually required, but you may need to fast for 8–12 hours before the draw if instructed. Bring a list of all medications (including over-the-counter drugs) you’re taking, as they can affect results.

How the Test Works

A blood sample is taken from a vein in your arm. The sample is then analyzed using an immunoassay method to detect and quantify erythromycin in your plasma or serum.

Possible Results and Interpretation

Results are typically reported in micrograms per milliliter (mcg/mL) or milligrams per liter (mg/L). Your provider will compare these values to your specific treatment plan to determine if your dose is appropriate.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Erythromycin levels help ensure therapeutic effectiveness—too little may mean the infection isn’t fully treated, while too much can lead to side effects like nausea, diarrhea, or drug interactions. Monitoring is especially important in patients with kidney or liver issues, as these organs process the drug.

Short name

Erythromycin Level

Frequently asked questions

What does an abnormal result mean?
An abnormal result could indicate improper dosing, drug resistance, or potential toxicity. Your provider will discuss these findings with you and may adjust your treatment plan if needed.
Can food or other medications affect this test?
Yes, certain medications (like antacids or other antibiotics) can interfere with erythromycin levels. Always inform your provider about all medications, supplements, or recent treatments.
How long will I need to wait for results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you once they’re ready to discuss the findings.
  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