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Levofloxacin trough serum concentration

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

This test measures the lowest amount of the antibiotic levofloxacin in your blood at a specific time after you’ve taken your medication.

Quick summary

["This helps doctors check if your antibiotic dose is working properly."]

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

Key facts at a glance

LOINC
30533-4
Short code
levoFLOXacin Trough SerPl-mCnc
Synonyms
levoFLOXacin Trough SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 doctor may order this test if you’re taking levofloxacin for a long-term infection, such as a urinary tract infection, pneumonia, or skin infection. It helps ensure the drug stays at an effective level in your blood without causing too much of an effect on your body.

What Does the Result Mean?

The result tells your healthcare provider whether your levofloxacin dose is sufficient to fight the infection. Too low levels may mean the infection isn’t being treated well, while too high levels could increase side effects.

How Is the Sample Collected?

A blood sample is drawn from a vein, usually in your arm. You may feel a small pinch when the needle is inserted, but it usually goes away quickly. You can usually return to your normal activities immediately after.

What Should You Expect Before the Test?

No special preparation is needed, but inform your doctor if you’re taking other medications, have allergies, or are pregnant. Avoid eating or drinking anything for at least 8 hours before the test if instructed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Trough Levofloxacin Level

Frequently asked questions

Why is a trough level checked instead of a peak level?
Trough levels are checked to ensure the antibiotic remains at a steady, therapeutic concentration in your bloodstream throughout the dosing interval. This helps prevent both underdosing (infection persistence) and overdosing (increased side effects).
What are common side effects of levofloxacin?
Common side effects may include nausea, diarrhea, or stomach pain. Rare but serious side effects can include tendon damage, nerve problems, or allergic reactions. Always report any unusual symptoms to your doctor.
Can I drink water before the blood draw?
Yes, you can drink water unless your doctor specifies otherwise. However, avoid eating or drinking anything for at least 8 hours before the test if instructed by your healthcare provider.
  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