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Doxycycline concentration in plasma

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

This test measures the amount of doxycycline, a type of antibiotic, in your blood plasma. It helps doctors check if the medication is working properly and at the right level in your system.

Quick summary

["This test helps ensure your doxycycline dose is appropriate for your treatment."]

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

Key facts at a glance

LOINC
73403-8
Short code
Doxycycline ind plt IgM SerPl Ql FC
Synonyms
Doxycycline 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 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 reaching safe levels in your blood.

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. The process is quick and usually painless.

What the Results Mean

Results help your doctor adjust your medication if needed. Low levels might mean the dose isn’t working well, while very high levels could indicate side effects or improper dosing.

Common Uses and Conditions

This test is commonly used for patients on long-term doxycycline therapy to prevent or treat infections, especially in conditions like acne, Lyme disease, or sexually transmitted infections.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Doxycycline is a broad-spectrum antibiotic used to treat bacterial infections. Monitoring its levels ensures effective treatment while minimizing risks of side effects. Low levels may require dose adjustments, while excessively high levels could signal toxicity or improper absorption.

Short name

Doxycycline Level

Frequently asked questions

Why might my doctor want to check my doxycycline levels regularly?
If you’re taking doxycycline for an ongoing infection or to prevent recurrence, your doctor may check levels to ensure it’s working as intended and to avoid side effects like nausea, stomach upset, or potential kidney/liver strain.
What if my doxycycline levels are too high or too low?
Too high could mean you’re experiencing side effects or the medication isn’t being absorbed properly. Too low might mean the infection isn’t fully treated. Your doctor will discuss changes to your dose if needed.
Can food or other medications affect this test?
Doxycycline absorption can be affected by certain foods (like dairy) or other medications (like antacids). Follow your doctor’s instructions about timing your dose relative to meals and other medications to ensure accurate results.
  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