Ceftriaxone Antibiotic Level (Serum)
This test measures the amount of ceftriaxone, a medication used to treat bacterial infections, in your blood. It helps doctors monitor how well your body is responding to the treatment.
["Your ceftriaxone levels help ensure the medication is working effectively and avoid unnecessary side effects."]
Key facts at a glance
- LOINC
- 25367-4
- Short code
- CEFTRI SGM
- Synonyms
- cefTRIAXone Islt SlowMyco
- Category
- chemistry
- Sample
- serum
- Container
- Sterile, leak-proof container for clinical specimens (e.g., sputum, bronchial washings, tissue, or body fluid). For serum-based assays, collect in a serum separator tube (SST) or red-top tube.
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- method-for-slow-growing-mycobacteria
- CPT
- 87181
- SNOMED
- 4361007
- Specimen volume
- Minimum 1 mL of specimen; 3-5 mL preferred for adequate testing
- Stability
- Specimens should be processed as soon as possible after collection. If processing is delayed, specimens should be refrigerated at 2-8°C for no more than 24 hours. Mycobacterial cultures should be processed in a biosafety level 3 (BSL-3) laboratory.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 168–720 hours
- Order
- routine
Why This Test Is Done
Doctors may order this test if you’re taking ceftriaxone to treat or prevent serious bacterial infections, such as pneumonia, meningitis, or urinary tract infections. It helps them check if the dose is appropriate and if the infection is responding to treatment.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into your vein (venipuncture) or a blood sample drawn from your arm. If you’re on a continuous IV infusion of ceftriaxone, your blood may be taken from the same site.
What the Results Mean
Results help doctors determine if your ceftriaxone levels are within the target range for your condition. Too little medication may mean the infection isn’t fully treated, while too much could increase side effects.
Possible Side Effects of Ceftriaxone
Ceftriaxone is generally safe, but high levels in the blood can sometimes cause nausea, diarrhea, or allergic reactions. Rarely, it may affect kidney or liver function, so monitoring is important.
Reference range
Interpretive criteria are reported as Susceptible (S), Intermediate (I), Resistant (R), or Susceptible-Dose Dependent (SDD) based on established MIC breakpoints for slow-growing mycobacteria. MIC values are reported in μg/mL.N/A
No special patient preparation is required prior to specimen collection. However, specimen collection should ideally occur before initiation of antimicrobial therapy when clinically feasible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Ceftriaxone Level
Frequently asked questions
What does a ‘positive’ or ‘negative’ result mean for this test?
How often will I need this test?
Can I eat or drink before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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