Sulfamethoxazole in Serum/Plasma (Quantitative Measurement)
This test measures the amount of the antibiotic sulfamethoxazole in your blood, helping your healthcare provider assess drug levels and monitor your treatment.
["This test helps ensure your dose of sulfamethoxazole is appropriate for your needs."]
Key facts at a glance
- LOINC
- 73141-4
- Short code
- Sulfamethoxazole ind plt IgM SerPl Ql FC
- Synonyms
- Sulfamethoxazole 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 doctor may order this test if you’re taking sulfamethoxazole (often combined with trimethoprim) to treat or prevent infections like urinary tract infections, pneumonia, or certain types of diarrhea. It may also be used to check if the drug is working properly or if adjustments to your dose are needed.
What to Expect Before the Test
No special preparation is usually required. You may be asked to fast for a few hours before the blood draw, but this depends on your doctor’s instructions. Bring a list of all medications you’re taking, including over-the-counter drugs and supplements.
What Happens During the Test
A healthcare provider will draw blood from a vein in your arm. You may feel a slight pinch, but it’s a quick procedure. The blood sample will be sent to a lab for analysis.
What the Results Mean
Results are typically reported as a concentration (e.g., micrograms per milliliter). Your doctor will interpret these results in relation to your medical condition, dose, and other factors. Low levels may indicate the drug isn’t working effectively, while very high levels could signal toxicity.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Sulfamethoxazole levels help prevent dangerous drug levels that could cause side effects like kidney problems, blood disorders, or allergic reactions. It’s especially important for patients with kidney disease or those taking other medications that interact with sulfamethoxazole.
Short name
Sulfamethoxazole Level
Frequently asked questions
How long does it take to get my results?
What does a low sulfamethoxazole level mean?
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