Tremor is an involuntary shaking movement that is repeated over and over. Although it may affect any part of the body, tremor most often affects the hands and head. Your voice may also shake. Occasionally the feet or torso may also shake.

Essential tremor, which sometimes runs in families, is one of the most common types of tremor. It is shaking that is most noticeable when you are doing something like lifting a cup or pointing at an object. The shaking does not occur when you are not moving. Medication can help reduce the shaking. Brain surgery can be helpful in some cases.

Tremors can also be caused by conditions or medications that affect the nervous system, including Parkinson's disease, liver failure, alcoholism, mercury or arsenic poisoning, lithium, and certain antidepressants. Side effects from other medications can also cause tremors.

If you notice a tremor, observe it carefully and note what seems to make it better or worse before calling your health professional. If a cause is discovered, the disease will be treated rather than the tremor.