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Test Code SQ UVALP, EPIC LAB172 Valproate, Unbound, Serum


Gas Chromatography

Includes total and unbound (free) valproate.

Note: Unbound level is not available after hours.

Performing Laboratory

University of Wisconsin Hospital and Clinics

Specimen Requirements

Specimen Type: Serum, cell free

Collection Container/Tube: Red top-Serum gel tube is not acceptable.

Submission Container/Tube: Plastic vial

Specimen Volume: 2 mL


NOTE: Serum only stable refrigerated for 24 hours and should be frozen for storage and delayed transport.

Specimen Transport Temperature

Refrigerated/Frozen OK

Reference Values

Total valproate

≥18 years: 50.0-125.0 mcg/mL

Critical value (automatic call-back): >150.0 mcg/mL


The therapeutic range for unbound valproate has not been established. The free fraction should be 7% to 15% when the total valproate is 50 mcg/mL to 100 mcg/mL, and 22% to 30% when the total is 125 mcg/mL to 150 mcg/mL.


Protein binding of valproic acid is concentration-dependent. Albumin sites will be saturated, in most individuals, when the total valproic acid level is near 100 mcg/mL. Any increase in dose will markedly increase the free drug level. The free fraction will increase in the presence of hypoalbuminemia. Free fatty acids may cause increased free valproate fraction.

Day(s) Test Set Up

Monday through Sunday (day shift)

Unbound level is not available after hours.

Test Classification and CPT Coding

80164 x 2