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Hydroxyzine concentration in serum/plasma (quantitative measurement)

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

This test measures the amount of hydroxyzine, a medication used to treat anxiety, allergies, or itching, in your blood.

Quick summary

["Knowing your hydroxyzine level helps doctors check if your dose is working safely."]

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

Key facts at a glance

LOINC
73339-4
Short code
hydrOXYzine ind plt IgG SerPl Ql FC
Synonyms
hydrOXYzine ind plt IgG 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 This Test Is Done

Your doctor may order this test if you’re taking hydroxyzine to monitor your response to the medication, check for side effects, or adjust your dose. It’s also used in cases of suspected overdose or to evaluate drug interactions.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample, usually drawn from a vein in your arm. If you’re on other medications or have recent illnesses, let your doctor know.

What the Test Results Mean

Results help determine if your hydroxyzine levels are within the safe range for your condition. Too little may mean the medication isn’t working, while too much could indicate side effects or toxicity.

Common Reasons for Testing

This test is most commonly used in clinical settings to assess therapeutic drug monitoring (TDM) for hydroxyzine, especially in patients with complex medical histories or those taking multiple medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Hydroxyzine levels provide critical information for managing side effects like drowsiness, dizziness, or low blood pressure. Abnormally high levels may signal overdose or poor metabolism, while low levels could indicate insufficient therapeutic effect. Doctors use these results to tailor treatment and avoid complications.

Short name

Hydroxyzine Level

Frequently asked questions

How long does it take to get results?
Results are typically available within 24 to 48 hours, depending on lab processing times and your healthcare provider’s workflow.
What does a low hydroxyzine level mean?
A low level may suggest the medication isn’t working as intended, possibly due to poor absorption, liver issues, or incorrect dosing. Your doctor may adjust your dose or explore alternative treatments.
Can I eat or drink before this test?
You can eat and drink normally before the test unless instructed otherwise. Avoiding food or fluids for a specific period isn’t required for this test.
  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