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Fexofenadine Concentration in Serum/Plasma

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

This test measures the amount of fexofenadine, an antihistamine medication, in your blood. It helps assess whether your dose is working as intended.

Quick summary

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

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

Key facts at a glance

LOINC
73022-6
Short code
Fexofenadine (neut) IgG SerPl Ql FC
Synonyms
Fexofenadine (neut) IgG SerPl Ql FC
Category
chemistry
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 This Test Is Done

Your healthcare provider may order this test if you’re taking fexofenadine (e.g., Allegra) for allergies and want to confirm your blood levels. It can also be used to monitor adherence to treatment or check for interactions with other medications.

What to Expect Before the Test

No special preparation is needed. You may have a simple blood draw from a vein in your arm. If you’re taking this medication regularly, your levels may be checked at different times (e.g., before or after doses).

What the Results Mean

Results help determine if your dose is within the therapeutic range. Abnormally high or low levels could indicate issues like poor absorption, drug interactions, or non-compliance. Your provider will discuss these findings with you.

Common Reasons for Testing

This test is often used in clinical settings to verify medication effectiveness, especially in patients who may have difficulty swallowing pills or those taking multiple medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Fexofenadine Levels Matter

Short name

Fexofenadine Level

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you with the findings.
Can I take my usual dose if my levels are low?
Not necessarily. Low levels might mean your body isn’t absorbing the medication well, so your provider may adjust your dose or check for other factors (e.g., liver function). Always follow their guidance.
Does this test interact with other medications?
Yes, some medications (e.g., certain antibiotics, antifungals) can affect fexofenadine levels. Your provider will review all your medications to avoid interactions.
  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