Valproic acid test: what the result means
Equals 50–100 mcg/ml (347–693 µmol/l) per MedlinePlus; mcg/ml = mg/l
- Updated
- 2026-09-10
- Every number with its source
What the valproic acid test is and why it is done
The valproic acid test measures the concentration of this medicine in the blood. It is not a marker the body produces itself but a drug monitoring (therapeutic monitoring) test: valproic acid is prescribed to treat certain types of seizures, to control mania in bipolar disorder and to prevent migraine attacks; the medicine acts on the nervous system of the brain. Because the effect depends on a sufficient concentration of the medicine in the blood, while too high a concentration can be harmful, doctors check the amount periodically to make sure it stays within the therapeutic range. According to MedlinePlus, for adults that range is 50–100 mcg/ml (347–693 µmol/l). A value below the range most often shows that the dose is insufficient or that the medicine is not being taken correctly; a value above the range may mean too high a dose or an interaction with other medicines and is linked to an increased risk of side effects, including liver damage. The result is always interpreted by a doctor together with the clinical picture and other tests.
Therapeutic range
| Group | Range, mg/l | Source |
|---|---|---|
| Adults, during treatment (therapeutic range) Equals 50–100 mcg/ml (347–693 µmol/l) per MedlinePlus; mcg/ml = mg/l | 50–100 | MedlinePlus Reviewed 2025-05-19 |
When the test is done
- When starting treatment with valproic acid or when the dose is changed — to make sure the concentration reaches the therapeutic range
- Regularly during treatment — to check whether the amount of the medicine in the blood stays steady and safe
- When the expected treatment effect is not achieved (for example, seizures do not become less frequent) — when too low a dose or incorrect use is suspected
- When signs of possible toxicity appear — drowsiness, a disturbed heart rhythm or disturbances of consciousness
- When signs of possible liver damage appear — tiredness, abdominal pain, nausea, yellowing of the skin or the eyes
- When other medicines or supplements that can interact with valproic acid are taken at the same time
How to prepare
- Do not stop or change how you take the medicine before the test, unless your doctor tells you otherwise
- Tell your doctor about every medicine and supplement you take — some can affect the amount of valproic acid in the blood
- Your doctor may give you a specific time for the blood draw in relation to when you take the medicine — follow those instructions
A result above the therapeutic range
An amount of valproic acid above the therapeutic range (50–100 mcg/ml per MedlinePlus) may mean too high a dose or an interaction with other medicines. This is linked to an increased risk of side effects, among them liver damage, so a doctor may adjust the dose and order additional tests.
Possible causes:
- Too high a dose is taken, or it is taken more often than prescribed (overdose)
- Pre-existing liver disease or impaired liver function — according to MedlinePlus, the doctor should be told about this before the medicine is prescribed
- An interaction with other medicines or supplements (for example, aspirin or cannabidiol/CBD) which, according to MedlinePlus, should be mentioned to the doctor before valproic acid is taken
Possible symptoms:
- Drowsiness
- An irregular heart rhythm
- Loss of consciousness (coma) — in severe toxicity
- Signs of liver damage: unusual tiredness, weakness, pain on the right side of the abdomen, loss of appetite, nausea, vomiting, dark urine, yellowing of the skin or the whites of the eyes
What usually follows:
- Discussing a possible dose adjustment with the doctor
- Liver function tests (for example ALT, AST) if there are signs of liver damage
- Reviewing the medicines and supplements taken alongside that can interact with valproic acid
- A repeat test after the dose is changed
A result below the therapeutic range
An amount of valproic acid below the therapeutic range (50–100 mcg/ml per MedlinePlus) most often means that the dose is insufficient or that the medicine is not being taken correctly. It can mean that the treatment effect (for example, seizure control) is not being achieved, so it is worth discussing with a doctor.
Possible causes:
- A missed dose of the medicine, or the prescribed schedule is not followed
- A smaller dose is taken than the doctor prescribed
- An interaction with other medicines or supplements, because of which, according to MedlinePlus, the doctor may adjust doses or monitor the patient more closely
What usually follows:
- Discussing a possible dose adjustment with the doctor
- Checking whether the medicine is being taken on the prescribed schedule
- A repeat test after the dose is changed
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Frequently asked questions
›What is the normal blood level of valproic acid?
According to MedlinePlus, the therapeutic range for adults treated with valproic acid is 50–100 mcg/ml (347–693 µmol/l). Your specific target range is set by your doctor according to the diagnosis and the goal of treatment.
›Why is the valproic acid test done?
This test is a therapeutic drug monitoring test. It checks whether the concentration of the medicine in the blood is sufficient for the treatment effect, but does not reach a level that would carry a risk of toxicity.
›What does too high a valproic acid level mean?
An amount above the therapeutic range may mean too high a dose or an interaction with other medicines. According to MedlinePlus, it is linked to symptoms such as drowsiness, an irregular heart rhythm or disturbances of consciousness, and to an increased risk of liver damage — the doctor should be told about this without delay.
›What does too low a valproic acid level mean?
An amount below the therapeutic range most often means that the dose is insufficient or that the medicine is not being taken correctly (for example, doses are missed). The treatment effect, such as seizure control, may then be insufficient — this is worth discussing with a doctor.
›Does the medicine have to be stopped before the test?
No; according to MedlinePlus the medicine must not be stopped or changed before the test without the doctor's instruction. The doctor may give a specific time for the blood draw in relation to when the medicine is taken.
›Why is the valproic acid test linked to liver markers?
Valproic acid is broken down in the liver, and too high a concentration of it is linked to possible liver damage, especially during the first months of treatment. A doctor therefore often assesses the result together with liver markers such as ALT or AST.
Sources
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.