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Doxycycline Serum/Plasma Concentration (Quantitative)

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

This test measures the amount of doxycycline, a type of antibiotic, in your blood. It helps determine whether your current dose is working effectively or if adjustments are needed.

Quick summary

["Check your antibiotic levels to ensure proper dosing and avoid side effects."]

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

Key facts at a glance

LOINC
20379-4
Short code
Doxycycline Islt SlowMyco
Synonyms
Doxycycline Islt SlowMyco
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
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 (an antibiotic) to treat infections like acne, urinary tract infections, or certain types of pneumonia. It helps monitor how much of the drug is in your blood to prevent resistance or toxicity.

What Does the Test Involve?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure doxycycline levels. No special preparation is needed, but fasting may be advised if your provider specifies it.

What Do Results Mean?

Results are compared to a general range, but exact values can vary by lab. High levels might indicate poor absorption or kidney issues, while low levels could mean the drug isn’t working as intended. Always discuss results with your provider.

Common Reasons for Testing

This test is often done during treatment to ensure the antibiotic is effective, especially for infections that don’t respond well to standard doses. It’s also used in cases where the patient has kidney problems or takes other medications that interact with doxycycline.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

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. Typically, it’s done during the first few days of therapy and sometimes later if needed. Follow their instructions closely.
What are the possible side effects of doxycycline?
Common side effects include nausea, stomach pain, or photosensitivity (increased sun sensitivity). Serious but rare side effects include kidney problems or allergic reactions. If you experience severe symptoms like rash, swelling, or trouble breathing, seek medical help immediately.
Can I drink alcohol while taking doxycycline?
No, it’s generally advised to avoid alcohol while on doxycycline, as it may increase the risk of liver problems or worsen side effects like nausea. Always check with your provider for personalized advice.
  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