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Beaumont Laboratory

Valproic Acid, Free

Depakene®, Depakote®, Valproate, Valproex®, ARUP #99310, EPIC: LAB6173, SOFT: XVALF

Specimen Collection Criteria

Collect: One plain Red-top tube.

Do not use Serum Separator Tubes.
Time of Collection: Trough, just prior to the next dose.

Physician Office/Drawsite Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells within two hours of collection. Transfer serum to a plastic transport tube and refrigerate (2-8°C or 36-46°F).

Preparation for Courier Transport

Transport: 2.0 mL serum, refrigerated (2-8°C or 36-46°F). (Min: 1.0 mL)

Rejection Criteria

  • Specimens not collected and processed as indicated.


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 1 month

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Sendout Laboratory with any questions.


Sent to ARUP Laboratories, Salt Lake City, UT.


Tuesday - Saturday.
Results available within 2-5 days.

Reference Range

Total Valproic Acid, Therapeutic: 50-125 mcg/mL.
Total Valproic Acid, Toxic: Greater than 150 mcg/mL.
Free Valproic Acid, Therapeutic: 7-23 mcg/mL.
Free Valproic Acid, Toxic: Greater than 30 mcg/mL.
Percent Free Valproic Acid: 5-18 percent.

Test Methodology

Quantitative Enzyme Multiplied Immunoassay Technique.


Free valproic acid may be important to monitor in patients with altered or unpredictable protein binding capacity because valproic acid exhibits variable, dose-dependent protein binding. Valproic acid is also subject to drug-drug interactions due to displacement of protein binding. Calculating percent free attempts to minimize differences in assay cross-reactivity and may be useful in dose optimization.

CPT Code


Test Codes


Last Updated


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This directory currently reflects information only for specimens collected and/or processed at the Farmington Hills, Grosse Pointe, Royal Oak, and Troy campuses.