Valproic acid is usually used to treat bipolar disorder.

Some brands are used to treat epilepsy. It can also be used to prevent migraine.

This medicine is only available on prescription. It comes as capsules or tablets.

If taken during pregnancy, valproic acid can cause problems for a baby's development, including birth defects and long term learning difficulties. For this reason, valproic acid is not recommended if there's a chance that you could become pregnant.

For women and girls of childbearing age, if you do need to take valproic acid then your doctor will put you on Prevent, the valproate pregnancy prevention programme.

• You'll usually take valproic acid 2 or 3 times a day. You can take it with or without food.
• You'll usually start on a low dose. Your dose will gradually increase over a few days or weeks.
• Sodium valproate and semisodium valproate are similar to valproic acid and work in the same way. However, these medicines are used to treat different conditions and doses will vary.
• There are also brands such as Epilim Chrono, Epilim Chronosphere and Dyzantil which contain mostly sodium valproate, with some valproic acid.
• If you're pregnant, or there's a chance you could become pregnant, valproic acid is not recommended for treating migraine. For epilepsy and bipolar disorder, your doctor will only prescribe valproic acid for you if there are no other suitable treatments.

Adults and children can take valproic acid to treat bipolar disorder or epilepsy.

Adults, aged 18 and above, can take it to prevent migraine.

Valproic acid is not suitable for girls or women who could become pregnant. However, in some cases it may be the only treatment option available, for example, for epilepsy where other treatments have not worked. Girls and women who need to take valproic acid must be on Prevent, the valproate pregnancy prevention programme.

To make sure valproic acid is safe for you, tell your doctor if you:

• have ever had an allergic reaction to valproic acid or any other medicine
• have liver problems
• have a rare metabolic or genetic condition such as porphyria, urea cycle disorder or mitochondrial disorder

Valproic acid is a prescription medicine. It's important to take it as your doctor tells you.

Dosage

The usual dose for treating bipolar disorder for:

• adults – 750mg to 2,000mg a day, split into 2 or 3 doses
• children – the doctor will work out the right dose for your child

The usual dose for preventing migraine for:

• adults – 500mg to 1,000mg a day, split into 2 or 3 doses

The usual dose for treating epilepsy for:

• adults and older children (aged 12 years and over) – 600mg to 2,000mg a day, split into 2 to 4 doses
• younger children (weighing more than 20kg) – the doctor will use your child's weight to work out the right dose for them

If you need to take your medicine more than once a day, you'll take equal doses that add up to your daily total. Ask your doctor or a pharmacist if you're unsure how much to take each time.

If you're taking valproic acid and have kidney problems, your doctor may prescribe a lower dose.

How and when take it

Valproic acid comes as gastro resistant tablets and capsules. These release the valproic acid into your body as soon as they pass through your stomach.

Swallow the tablets or capsules whole with a drink of water or juice. Do not chew them.

You can take valproic acid with or without food, but it's best to do the same each time.

If you're taking valproic acid twice a day, try to leave a gap of 10 to 12 hours between doses. For example you could take your first dose in the morning (between 7am and 8am) and your second dose in the evening (between 7pm and 8pm).

If you take it 3 to 4 times a day, try to space your doses evenly throughout the day. If you need to take 3 doses, for example, you could take a dose first thing in the morning, early afternoon and bedtime.

Will my dose go up or down?

To reduce the chance of side effects, your doctor will start you off on a low dose of valproic acid. They will increase it gradually over a few days or weeks.

Once you find a dose that suits you, it will usually stay the same, unless your condition changes, or your doctor starts you on a new medicine that may interfere with valproic acid.

What if I forget to take it?

If you forget a dose, take it as soon as you remember, unless it's less than 2 hours to your next dose. In this case, skip the missed dose and take your next one at the usual time.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you have epilepsy, it's important to take this medicine regularly. Missing doses can trigger a seizure.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Taking too much valproic acid can lead to symptoms such as:

• feeling or being sick (nausea or vomiting)
• headaches, or feeling dizzy
• muscle weakness
• breathing problems
• feeling confused, or changes to your normal behaviour
• passing out

Like all medicines, valproic acid can cause side effects, although not everyone gets them.

Common side effects

These common side effects may happen in more than 1 in 100 people. They're usually mild and go away by themselves.

Keep taking the medicine but talk to your doctor if these side effects bother you or do not go away:

• stomach pain, feeling or being sick
• diarrhoea
• dry or sore mouth, or swollen gums
• shakes (tremors) in a part of your body, or unusual eye movements
• feeling tired or sleepy
• headache
• weight gain
• thinning hair, or changes to the colour or texture of your hair
• irregular or delayed periods

Serious side effects

It's unusual to have serious side effects after taking valproic acid. Tell a doctor straight away if you have:

• thoughts of harming or killing yourself – a small number of people taking valproic acid have had suicidal thoughts
• yellowing of the whites of your eyes or your skin, although this may be less obvious on brown or black skin, and dark pee – these may be signs of liver problems
• long-lasting and severe nausea, vomiting or stomach pain – these may be signs of acute pancreatitis (an inflamed pancreas)
• unusual bruises or bleeding – these may be signs of a blood disorder

Serious allergic reaction

In rare cases, valproic acid may cause a serious allergic reaction (anaphylaxis).

What to do about:

• stomach pain, feeling or being sick – take valproic acid with or after a meal or snack. It may also help if you avoid rich or spicy food. Take small, frequent sips of water if you're being sick to avoid dehydration.
• diarrhoea – drink plenty of fluids such as water or squash to avoid dehydration. Speak to a pharmacist if you have signs of dehydration, such as peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
• dry or sore mouth, or swollen gums – for a dry mouth try sugar-free gum or sweets, or sipping cold drinks. If this does not help, or you have mouth ulcers, talk to your pharmacist or doctor. If you're bothered by swollen gums or this symptom does not go away, talk to your doctor or dentist.
• shakes (tremors) in a part of your body, or unusual eye movements – talk to your doctor if this is bothering you. These symptoms can be a sign that your dose is too high. Talk to your doctor as they may want to change your dose or suggest you take it at a different time.
• feeling tired or sleepy – as your body gets used to valproic acid, these side effects should wear off. If these symptoms do not get better within a week or two, your doctor may either reduce your dose or increase it more slowly. If that does not work, talk to your doctor as they may want to switch you to a different medicine.
• headaches – make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller. Talk to your doctor if your headaches last longer than a week or are severe.
• weight gain – if you find you're putting on weight after taking valproic acid, try to have a healthy balanced diet. Regular exercise will also help you keep your weight stable. Your doctor will usually monitor your weight while you're taking this medicine. Speak to them if you have any concerns.
• thinning hair, or changes to the colour or texture of your hair – if these symptoms bother you, ask your doctor whether it's possible to lower your dose. Your hair may regrow after either reducing your dose or switching to a different medicine.
• irregular or delayed periods – if you usually have regular periods, take a pregnancy test if your period is late, and speak to your doctor if the result is positive. As well as being a side effect of valproic acid, a late period is a sign that you could be pregnant, and valproic acid can be harmful for an unborn baby. Changes to your periods can also be a symptom of polycystic ovary syndrome (PCOS), a rare side effect of valproic acid. Your doctor will be able to do some tests to check whether you have PCOS.

Valproic acid is not recommended in pregnancy, as it can cause birth defects and problems with your baby's learning and behaviour.

If there's a chance you could become pregnant while taking this medicine, your doctor will put you on Prevent, the valproate pregnancy prevention programme.

If you think you might already be pregnant, contact your doctor or nurse as soon as possible.

If you're taking valproic acid for epilepsy or bipolar disorder and you become pregnant, do not stop taking your medicine without talking to your doctor first. This is because your symptoms may get worse.

Your doctor may continue to prescribe valproic acid, but only if there's no other suitable treatment for your epilepsy or bipolar disorder.

For pregnant women with recurrent migraine your doctor should offer you an alternative treatment to valproic acid.

• Best Use of Medicines in Pregnancy (BUMPS) website – information about how valproic acid can affect you and your baby during pregnancy
• NHS England letter to all women and girls aged 12 to 55 taking sodium valproate (includes valproic acid), available in different languages
• Valproate pregnancy prevention programme patient guide: what women and girls need to know about valproate (PDF, 341kb)

There are some medicines that may affect how valproic acid works. Valproic acid can also affect the way other medicines work.

Tell your doctor if you're taking any of these medicines:

• any other medicines for epilepsy such as carbamazepine
• medicines for preventing blood clots such as warfarin
• aspirin for pain relief or low-dose aspirin
• cimetidine, a medicine for stomach ulcers
• medicines to treat HIV and AIDS such as ritonavir
• antibiotics such as erythromycin
• medicines for depression or other mental health problems such as venlafaxine, quetiapine or diazepam
• cholesterol-lowering medicines such as cholestyramine
• medicines to prevent malaria such as mefloquine or chloroquine

Mixing valproic acid with herbal remedies or supplements

It's not possible to say whether complementary medicines and herbal supplements are safe to take with valproic acid.

They're not tested in the same way as pharmacy and prescription medicines. They're generally not tested for the effect they have on other medicines.