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Fexofenadine Concentration in Serum or Plasma

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

This test measures the amount of fexofenadine, a medication used to relieve symptoms of allergies like itching, sneezing, and runny nose, in your blood.

Quick summary

["Helps monitor your dose of allergy medication."]

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

Key facts at a glance

LOINC
73021-8
Short code
Fexofenadine (neut) IgM SerPl Ql FC
Synonyms
Fexofenadine (neut) IgM 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) and want to ensure your dose is working properly. It can also help check for drug levels if you have kidney issues or take other medications that might affect how fexofenadine is processed in your body.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm or vein to draw a blood sample. If you’re taking this test for kidney function monitoring, your doctor may ask you to follow a specific diet or timing before the test.

What the Results Mean

Results show the concentration of fexofenadine in your blood. While reference ranges vary by lab, lower-than-expected levels might suggest your medication isn’t being absorbed well, while very high levels could indicate issues with how your body processes it.

Common Reasons for Testing

This test is often used to verify therapeutic drug levels, especially in patients with kidney problems or those taking multiple medications that could interact with fexofenadine.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Fexofenadine Levels Help Assess Treatment Effectiveness and Safety

Short name

Fexofenadine Level

Frequently asked questions

How long does it take to get results from this test?
Results are typically available within 1 to 3 business days, depending on your lab and healthcare provider’s workflow. Your doctor will discuss the findings with you during your follow-up visit.
Can I eat or drink anything before this blood test?
No special diet or fasting is required unless instructed by your doctor. However, avoid caffeine or alcohol before the test if they may affect your bloodwork results.
Is there any risk or discomfort with this test?
Most people experience only mild discomfort from the needle stick, which usually goes away quickly. Rarely, some people may feel slight bruising or swelling at the injection site. If you have a fear of needles, let your healthcare provider know so they can discuss alternatives.
  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