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Paroxetine concentration in plasma

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

This test measures the amount of paroxetine, a medication used to treat depression, anxiety, and other mental health conditions, in your blood.

Quick summary

["Knowing your paroxetine levels helps your doctor monitor your dose and adjust it for optimal effectiveness and safety."]

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

Key facts at a glance

LOINC
73214-9
Short code
PARoxetine ind plt IgM SerPl Ql FC
Synonyms
PARoxetine ind plt IgM 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 paroxetine (brand names like Paxil) to check if your dose is working well. It can also help identify if you’re experiencing side effects or if your body is metabolizing the drug too quickly or slowly.

What to Expect Before the Test

No special preparation is needed. You’ll have a small needle inserted into your arm or vein to draw a blood sample. It usually takes a few minutes, and you may feel a brief pinch. If you’re on blood thinners, let your doctor know before the test.

What the Results Mean

Results are used to guide your treatment. Low levels might mean your dose isn’t high enough, while very high levels could signal potential side effects or issues with how your body processes the drug. Your doctor will interpret these results in the context of your overall health and symptoms.

Common Reasons for Testing

Doctors may test paroxetine levels if you’re struggling with side effects like nausea, dizziness, or fatigue; if your symptoms aren’t improving; or if you’re considering stopping the medication.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Paroxetine Level

Frequently asked questions

What does a paroxetine level tell your doctor?
It helps assess whether your current dose is safe and effective. For example, low levels might mean your dose needs to be increased, while very high levels could indicate problems like drug interactions, liver issues, or improper metabolism.
How often should I get this test?
Your doctor will determine the timing based on your treatment plan. Typically, it’s done during regular check-ups or if you’re experiencing changes in symptoms or side effects.
Can diet or other medications affect this test?
Yes. Certain foods, supplements, or other medications (like grapefruit juice or some antidepressants) can interact with paroxetine. Always tell your doctor about all medications, herbs, or dietary changes before testing.
  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