Doxycycline concentration in plasma or serum (quantitative measurement)
This test measures the amount of doxycycline, a type of antibiotic, in your blood. It helps doctors check if your dose is working properly and if you’re responding to treatment.
["This test helps monitor antibiotic levels to ensure safety and effectiveness."]
Key facts at a glance
- LOINC
- 25223-9
- Short code
- Doxycycline Islt Slgr Mcbct AB 30.0
- Synonyms
- Doxycycline Islt Slgr Mcbct AB 30.0
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- method-for-slow-growing-mycobacteria-antibiotic-concentration-at-ug-ml
- 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
Doctors may order this test if you’re taking doxycycline to treat infections like acne, urinary tract infections, or certain types of pneumonia. It helps them adjust your medication to avoid side effects while staying effective.
What to Expect Before the Test
No special preparation is needed. You’ll likely have a small needle inserted into your arm or vein to draw a blood sample. If you’re on doxycycline, your doctor may ask you to stop taking it temporarily before testing, depending on the protocol.
What the Results Mean
Results show how much doxycycline is in your blood at the time of testing. Low levels may mean the antibiotic isn’t working well, while very high levels could indicate side effects. Your doctor will interpret these results in the context of your treatment plan.
Possible Side Effects or Considerations
Doxycycline can cause side effects like nausea, stomach upset, or photosensitivity (increased sensitivity to sunlight). If you experience severe reactions, contact your doctor immediately. Avoid taking this test if you’re pregnant, breastfeeding, or have certain kidney or liver conditions.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Monitoring doxycycline levels is critical for patients with infections resistant to other antibiotics or those at risk of toxicity. It ensures optimal dosing to prevent resistance while minimizing harm. Results guide adjustments to dosing frequency, duration, or alternative treatments if needed.
Short name
Doxycycline Level
Frequently asked questions
Will I need to stop taking doxycycline before the test?
What does a ‘low’ or ‘high’ doxycycline level mean?
Can I drink water or eat before the blood draw?
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