Laboratory Services

Valproic Acid, Free, Serum

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Updated Test Information:

Test Description
Valproic Acid, Free, Serum

Divalproex ,Valproate, Depakene (Valproic Acid), Depakane (Valproic Acid), Free Valproic Acid, Valproic Acid, Free and Total, VALPROIC ACID, FREE

Test ID
General Information

Useful for monitoring free valproic acid in therapy, assessing compliance, evaluating potential toxicity

Container Type

Preferred: SST
Acceptable: Red Top Tube

Specimen Type


Specimen Requirements


Specimen Collection / Processing Instructions

1. SSTs should be centrifuged within 2 hours of collection.
2. Red Top Tubes should be centrifuged and aliquoted within 2 hours of collection.

Minimum Sample Volume



Refrigerated (preferred): 14 days
Frozen: 28 days
Ambient: 72 hours

Unacceptable Specimen Conditions

Gross hemolysis


Ultrafiltration Followed by Immunoassay

Estimated TAT

1-2 Days

Testing Schedule



7 Days

CPT Code(s)


Reference Range

Therapeutic: 5-25 mcg/mL

Critical value: >30 mcg/mL

Performing Lab


LOINC Code(s)


Collection File View/Download File
Additional Information

The generally acceptable range for total valproic acid used as a reference to guide therapy is 50 to 125 mcg/mL. The corresponding range of free valproic acid concentration for clinical reference is 5 to 25 mcg/mL.

Low free valproic acid concentration relative to these ranges may suggest inadequate dosing, whereas a high free valproic acid concentration may be associated with toxic effects.

 Because the concentration of valproic acid fluctuates considerably depending on the time from last dose, interpretation of the clinical significance of the valproic acid concentration must take into consideration the timing of the blood specimen. For this reason, 2 collections are sometimes made to assess the trough and peak concentrations.