Valproic Acid, Free, Serum or Plasma

CPT: 80165
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Test Details


  • Depacon®
  • Depakene®
  • Depakote®
  • Free Valproic Acid
  • Stavzor™
  • Valproate


Since valproic acid is highly bound, drugs that compete for protein binding sites can increase the amount of free valproic acid (biologically active protein); these include dicumarol, high dose salicylates, and phenylbutazone. If toxicity is suspected, a free valproic acid level should be obtained.


Ultrafiltrate assayed by liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference Interval

Therapeutic: 6.0-22.0 μg/mL

Specimen Requirements


Serum or plasma


3 mL

Minimum Volume

1.1 mL


Red-top tube or lavender-top (EDTA) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant.


Transfer separated serum or plasma to a plastic transport tube.

Storage Instructions

Room temperature

Stability Requirements



Room temperature

14 days


14 days


14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Gel-barrier tube; hemolysis; serum or plasma not removed from cells

Clinical Information


Jacobson SA. Laboratory Medicine in Psychiatry and Behavioral Science. Washington, DC: American Psychiatric Publishing; 2012:368.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
070789 Free Valproic Acid (Depakote) 4087-3 070790 Free Valproic Acid (Depakote) ug/mL 4087-3

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