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Serum/plasma concentration of doxycycline (antibiotic drug level)

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

This test measures the amount of doxycycline, a prescription antibiotic, in your blood. It helps doctors check if your dose is working properly and if you’re responding to treatment.

Quick summary

["This test ensures your antibiotic levels are safe and effective."]

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

Key facts at a glance

LOINC
73402-0
Short code
Doxycycline ind plt IgG SerPl Ql FC
Synonyms
Doxycycline 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 Is This Test Done?

Your healthcare provider may order this test if you’re taking doxycycline to treat infections like acne, urinary tract infections, or certain types of pneumonia. It helps monitor whether the medication is at an appropriate level in your bloodstream to fight bacteria without causing harmful side effects.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or a blood sample drawn from a vein. If you’re on a long-term course, your provider may ask you to fast or avoid certain foods/drugs for a set time before testing.

What the Results Mean

Results are typically reported as a concentration (e.g., micrograms per milliliter). Low levels may mean the antibiotic isn’t working well, while very high levels could indicate toxicity. Your provider will interpret these results in the context of your treatment plan.

Common Reasons for Testing

Doctors may check doxycycline levels if you’re experiencing side effects (like nausea or kidney issues), if the infection isn’t improving, or if you’re taking other medications that could interact with doxycycline.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Monitoring Antibiotic Effectiveness and Safety

Short name

Doxycycline Level

Frequently asked questions

How often should I get this test?
Your provider will determine the timing based on your treatment plan. For short courses, it might be done once or twice during therapy. For long-term use, tests may be scheduled more frequently to adjust dosing if needed.
Can I eat or drink anything before the test?
Generally, you can eat and drink normally unless instructed otherwise by your provider. Some tests require fasting, but doxycycline blood levels are typically checked without dietary restrictions.
What are typical side effects of doxycycline?
Common side effects include stomach upset, nausea, or photosensitivity (increased sun sensitivity). Rarely, very high levels can cause kidney or liver issues. Always report unusual symptoms to your doctor.
  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