Most people who take carbamazepine 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 mild to moderate in severity) are:

• dizziness
• sleepiness
• unsteadiness
• upset stomach
• blurred or double vision
• headache

Sometimes the doctor can help with these side effects by changing the prescription:

• reducing the overall amount of carbamazepine
• prescribing smaller doses, taken more often
• changing the prescription from regular carbamazepine to an extended-release form, like Tegretol-XR or Carbatrol.

No one should stop taking carbamazepine or change the amount they take without their doctor's guidance.

People who have just started taking carbamazepine (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.

Other side effects of carbamazepine that are much less common include:

• vomiting
• a low level of sodium in the blood, which causes dizziness, tiredness, confusion, or increased seizures (more common in older people and those with heart disease)
• pain in the abdomen
• constipation
• diarrhea (if this happens, it may help to limit your intake of lactose-containing foods, such as dairy products)
• loss of appetite

Allergic reactions
About 5% to 10% of people who take carbamazepine have a red rash within the first month of taking it. If this happens, tell the doctor or nurse, to be sure that it's not the beginning of a serious problem. During this time, it's a good idea to avoid too much sunlight, which may increase the risk of rash.

About half the time the rash will go away on its own and will not come back. Stopping the carbamazepine for a day or two (with the doctor's OK) and then starting it again seems to help. Other people need to stop taking it permanently, and some use another medicine to treat the rash itself. The doctor can advise on which is the best strategy for each person.

Long-term side effects
Some doctors suspect that the bones of some people who take carbamazepine for years may become thin and weak, though this effect has not yet been proven. It may happen because carbamazepine can interfere with the way the body uses vitamin D. This vitamin is needed to help the bones absorb calcium. People who take carbamazepine should be careful to get plenty of vitamin D and calcium every day. They also should exercise to keep their bones strong. Ask the doctor for advice on the proper doses of vitamin D and calcium. The doctor also can say whether a bone density test is advised.