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Test Code VALPF Valproic Acid, Free, Serum

Performing Laboratory

LabCorp Burlington NC


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


TAT: 3 - 5 Days

Reference Values

Therapeutic: 6.0 - 22.0  ug/mL

Test Classification and CPT Coding



LOINC: 4087-3

Specimen Required

Container/Tube:  Plain, red-top tube(s)

Specimen:  3 mL of serum (1.1 mL min)

Transport Temperature:  Refrigerate


Stability:  14 Days Room Temperature 

                 14 Days Refrigerated

                14 Days Frozen


Do not use gel barrier tubes. Centrifuge and immediately separate serum or plasma specimens from the cells into clean, plastic, screw-cap vial(s).
Do not use serum separator tubes. Submission of a serum separator tube will result in cancellation


Patient Preparation

Avoid contact of samples with plasticizers, varnishes, paint fumes, and fatty acids. Collect as a trough just before next dose (Optimum time to collect sample: 1 hour before next dose.).

Computer Interface Code

PDM #  5400266

Usedn For

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.