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Benzylpenicillin (Penicillin G) Level in Serum/Plasma

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

This test measures the amount of benzylpenicillin (penicillin G) in your blood, which helps monitor how your body is responding to penicillin antibiotics.

Quick summary

["This test helps ensure your penicillin treatment is working effectively and at safe levels."]

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

Key facts at a glance

LOINC
73506-8
Short code
Benazepril ind plt IgG SerPl Ql FC
Synonyms
Benazepril 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 penicillin (such as benzylpenicillin) to treat bacterial infections like syphilis, meningitis, or other serious infections. It helps check if the antibiotic is reaching the right amount in your bloodstream to fight the infection without causing harmful side effects.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw blood. It usually takes a few minutes. If you’re on long-term penicillin therapy, your provider may schedule regular tests to monitor levels.

How the Test Results Are Used

Results help determine if your penicillin dose is appropriate. Low levels may mean the antibiotic isn’t working well, while high levels could indicate side effects or improper dosing. Your provider will discuss findings with you.

Possible Side Effects or Risks

Blood tests are generally safe, but rare risks include bruising, pain at the injection site, or fainting. If you’re allergic to penicillin, let your provider know before testing.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Penicillin Level

Frequently asked questions

What does a low level of penicillin mean?
A low level may suggest the infection isn’t fully treated or that the antibiotic isn’t being absorbed properly. Your provider may adjust your dose or consider alternative treatments.
What does a high level of penicillin mean?
High levels could indicate overdosage, allergic reactions, or kidney issues affecting metabolism. Your provider will review symptoms and lab results to guide next steps.
Why are regular penicillin level checks important?
Regular monitoring helps prevent infections from worsening, avoids antibiotic resistance, and ensures safe dosing—especially for serious or long-term treatments.
  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