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Valproate Bound, Serum/Plasma — Mass Fraction

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

Measures the proportion of valproate, an antiseizure medicine, that is bound to proteins in blood.

Quick summary

["This test helps determine how much valproate is protein-bound, which can affect the amount of active medication available to the body."]

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

Key facts at a glance

LOINC
21590-5
Short code
Valproate Bnd MFr SerPl
Synonyms
Valproate Bnd 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 blood test measures the fraction of valproate that is bound to proteins. Valproate is used to treat seizures and certain other conditions. Some valproate travels freely in the blood, while the rest is attached to proteins.

Why might I need this test?

Your clinician may order this test when monitoring valproate treatment, especially if symptoms suggest that the medication level is too low or too high despite a seemingly acceptable total level. Changes in blood proteins or other medicines can alter how strongly valproate binds to proteins.

How is the test performed?

A blood sample is collected and analyzed in the laboratory. The result may be measured directly or calculated by comparing total valproate with the unbound portion, depending on the laboratory's method.

How do I prepare for the test?

No special preparation is usually required. Follow your clinician's instructions about the timing of the blood draw, and do not change or stop taking valproate without medical guidance.

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

Valproate protein binding

Frequently asked questions

What does a bound valproate result mean?
It shows the proportion of valproate attached to blood proteins rather than circulating freely. The unbound fraction is the portion immediately available to exert its effect.
Why are both total and bound valproate sometimes checked?
A total level includes both bound and unbound valproate. Checking the bound fraction can help clarify the active free level when the total result does not match the person's symptoms.
What factors can change valproate protein binding?
Changes in blood proteins, pregnancy, and certain other medicines can affect valproate binding. These factors are considered when the laboratory result is interpreted.
  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