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Free Valproate, Serum/Plasma — Mass Fraction

Published: August 9, 2026Updated: August 17, 2026

Measures the unbound valproate level in serum or plasma, which reflects the portion of the medication available to the body.

Quick summary

["This test can help assess valproate exposure and guide safe medication dosing."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
32283-4
Short code
Valproate Free MFr SerPl
Synonyms
Valproate Free MFr SerPl
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
44
Ref high
147
Critical range
— – 151 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84075
SNOMED
27550007
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test measures free valproate in serum or plasma. Free valproate is the portion of the medicine not bound to blood proteins and is available to the body.

Why might I need this test?

Your clinician may order it to monitor valproate treatment, investigate possible medication toxicity, or adjust the dose. It may be especially useful when your health condition or another medicine could affect how valproate binds to proteins.

How is the test performed?

A blood sample is collected by venipuncture, usually from a vein in the arm. The laboratory separates serum or plasma and measures the free valproate fraction using a validated laboratory method.

How do I prepare for the test?

Take valproate as prescribed and tell your clinician about all medicines and supplements you use. Do not stop or change your dose unless your clinician directs you to do so; timing of the blood draw relative to doses may be important.

Reference range

Adult: 44-147 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Valproate

Frequently asked questions

How is free valproate different from a total valproate test?
A total valproate test measures both protein-bound and unbound medication, while this test measures only the unbound fraction that is available to the body.
Does the time I take valproate affect the result?
Yes. Valproate levels can change after a dose, so your clinician may specify when the blood sample should be collected. Follow the collection instructions exactly.
Can another medicine affect free valproate levels?
Yes. Medicines that displace valproate from blood proteins or alter its metabolism can change the free level. Your clinician should review all prescription medicines, over-the-counter products, and supplements.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy