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Amoxicillin Concentration in Serum or Plasma

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

This test measures the amount of the antibiotic amoxicillin in your blood to check if it’s working properly and at the right level.

Quick summary

["Amoxicillin levels help ensure your treatment is effective and avoid potential side effects."]

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

Key facts at a glance

LOINC
50-5
Short code
BACSBT
Synonyms
Bacampicillin Titr SBT
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or red-top tube without anticoagulant
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Serum bactericidal titer (microdilution or tube dilution method)
CPT
87197
SNOMED
104195008
Specimen volume
1–2 mL of serum
Stability
Serum stable for 2 hours at room temperature; 24 hours at 2–8°C; frozen at -70°C for longer storage
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

Why This Test Is Done

Your healthcare provider may order this test if you’re taking amoxicillin (a penicillin antibiotic) to treat or prevent infections. They might also check it if you have trouble absorbing medications or if you’re being monitored for side effects.

How the Test Works

A blood sample is taken from a vein in your arm. The sample is then tested using a method called immunoassay (IA) to measure the amount of amoxicillin present in your serum or plasma.

What to Expect Before the Test

No special preparation is needed, but let your provider know if you’re taking other medications or have allergies, as this may affect results.

What the Results Mean

Results help determine if your amoxicillin dose is correct. High levels may indicate poor absorption or kidney issues, while low levels could mean the medication isn’t working as intended.

Reference range

Titer ≥ 1:8 is generally considered indicative of adequate bactericidal activity; results reported as the highest dilution of serum that kills ≥ 99.9% of the bacterial inoculumN/A

Specimen: serum

No special preparation required. Specimen should be collected at peak (approximately 30–60 minutes post-dose) and trough (just before next dose) intervals for accurate interpretation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Amoxicillin Level

Frequently asked questions

How can I prepare for this blood test?
No dietary restrictions are needed, but inform your doctor about all medications, including over-the-counter drugs or supplements, to avoid false results.
What are the typical reference ranges for this test?
Reference ranges vary by lab and patient factors, so your results will be interpreted by your healthcare provider based on your specific situation.
Can I eat or drink before this test?
You can eat and drink normally unless instructed otherwise by your provider, as fasting isn’t required for this 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