Most people who take valproic acid don't have too much trouble with side effects. That's one of the reasons it’s used so much. The most common complaints (usually not too severe) are:

• tiredness (sometimes with slower thinking)
• dizziness
• upset stomach
• vomiting
• tremor
• hair loss
• weight gain
• behavioral changes (depression in adults, irritability in children)

If these problems do not go away within several days or are really bothersome, call the doctor. Sometimes the doctor can help with these side effects by changing the prescription:

• reducing the overall amount of valproic acid
• prescribing smaller doses, to be taken more often
• changing the amount taken at certain times, such as taking a greater proportion of the valproic acid at bedtime to reduce daytime sleepiness
• prescribing the extended-release valproate product, Depakote ER, which gives a steadier level of medicine in the blood

No one should stop taking valproic acid or change the amount they take or when they take it without their doctor's guidance.

People who have just started taking valproic acid (or who have just started taking a larger amount) should be careful during activities that might be dangerous, until they know whether they are having any side effects.

Taking valproic acid on a full stomach may help to reduce stomach upset. Stomach upset from valproic acid is more likely when another seizure medicine with similar side effects (for example, Tegretol) is also being used.

Tremor (shaking of the hands or other body parts) tends to be worse at some times than others. It 's usually most noticeable when the level of valproic acid in the blood is highest, a few hours after a dose is taken. Anxiety or caffeine also may make it worse.

Weight gain affects 30% to 50% of people who take valproic acid. It is more common in adult women but can affect anyone. The average gain for adults is 15 pounds. Exercise and a reduced-calorie diet can be very helpful. It's uncertain whether weight gain is greater when higher doses of valproic acid are taken.

Hair loss occurs in 5% to 10% of patients taking valproic acid. The hair almost always grows back after the valproic acid is stopped, but it often has a different texture. (For example, it may grow in curly instead of straight.) Taking selenium (10-20 mcg per day) and zinc (25-50 mg per day) helps some people to prevent hair loss.

Allergic reactions
Allergic reactions such as rashes are less common with valproic acid and other forms of valproate than with most other seizure medicines. Even so, you should report any rash to the doctor or nurse right away, especially if valproic acid treatment has just begun. It's rare for the rash to be serious, but don't ignore it. It's often necessary to switch to a different seizure medicine.

Some other rare but life-threatening disorders do occur with the use of this medication. Children younger than 2 years of age and those taking other seizure medications in addition to valproic acid are at highest risk. See Serious side effects.

Long-term side effects
Some people who have taken valproic acid or other valproate products for many years have experienced bone loss, ankle swelling, or irregular menstrual periods. Taking supplements of both calcium and vitamin D may help to prevent bone loss. Increasing numbers of doctors are advising people who have taken any form of valproate for more than 5 years to have a bone density test. If the test shows much thinning of the bones, the person may need to see a doctor who specializes in bone metabolism.