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Involuntary Shaking - Trembling

Overview, Causes, & Risk Factors

The term trembling is generally used to describe involuntary or unintentional shaking.

What is going on in the body?

Many people have experienced trembling before. It can happen when a person is cold or nervous. However, trembling has many causes, and some of those causes can be quite serious.

What are the causes and risks of the condition?

There are many possible causes of trembling. These include:

  • strong emotion, such as fear, anger, or anxiety
  • stress or fatigue
  • being cold. This can simply be due to feeling chilled or a more serious condition such as hypothermia, or low body temperature.
  • benign essential tremor, sometimes called senile tremor. This is often an inherited condition that causes mild trembling with no other symptoms.
  • hyperthyroidism, or a level of thyroid hormone in the body that is too high
  • certain drugs or medications. Examples include:
  • prednisone, commonly used to reduce inflammation
  • caffeine
  • albuterol, used in the treatment of asthma
  • some medications used for psychatric conditions, such as haldol
  • withdrawal from alcohol
  • damage to the central nervous system. Damage to areas of the brain called the cerebellum and basal ganglia are most likely to cause trembling. Basal ganglia disorders include Parkinson's disease and Huntington disease. Strokes, or brain attacks, can also cause brain damage that may result in trembling.
  • kidney or liver failure, which can cause a type of trembling called asterixis
  • seizures, or epilepsy, which occur due to abnormal electrical activity in the brain
  • myoclonus, a condition that results in brief, quick movements of one or more muscles. This can be due to Alzheimer disease, kidney failure, or a head injury, among other causes.
  • tics, a type of quick, repeated movement. This may be the result of condition called Tourette syndrome or other conditions.
  • hypoglycemia, or low blood sugar
  • a tumor or cancer, such as a brain tumor
  • Other causes are also possible. Sometimes, no cause can be found.

    Symptoms & Signs

    What are the signs and symptoms of the condition?

    When a person complains of trembling, the healthcare provider will want to know:

  • exactly what the trembling is like
  • when the trembling started
  • whether it is constant or occurs only sometimes
  • what areas of the body are affected, such as the whole body or only one arm
  • whether the trembling is related to movement or occurs at rest
  • whether there is any family history of trembling
  • what medications the person may be taking
  • what medical conditions the person may have
  • any other symptoms the person may be having
  • Other questions may also be asked.

    Diagnosis & Tests

    How is the condition diagnosed?

    Diagnosis begins with the history and physical exam. This may be all that is needed to figure out the cause. Further tests are needed in other cases.

    The tests ordered will depend on the suspected cause. For example, thyroid function blood tests can detect hyperthyroidism. A blood glucose level can detect hypoglycemia.

    An electroencephalogram, or EEG, is a test that can be used to detect seizures. It involves taping several wires to the scalp to measure the electricity in the brain, often called brain waves. Special x-rays of the brain, such as a cranial CT scan, may be ordered if brain damage is suspected.

    Prevention & Expectations

    What can be done to prevent the condition?

    Prevention is related to the cause. Most cases cannot be prevented. Avoiding alcohol can prevent cases due to alcohol withdrawal. Avoiding the cold can prevent some cases due to feeling chilled.

    What are the long-term effects of the condition?

    Long-term effects are related to the cause. For example, cases due to cold or fatigue often have no long-term effects. Cases due to nervous system damage may result in death or permanent disability.

    What are the risks to others?

    Trembling is not contagious and poses no risk to others.

    Treatment & Monitoring

    What are the treatments for the condition?

    Treatment is directed at the cause, if one can be found. For example, myoclonus can often be treated with medications called benzodiazepines, such as diazepam. Someone who trembles because of seizures can be treated with medications to stop the seizures, such as gabapentin. Those with kidney failure may need a kidney transplant or dialysis, a procedure to filter the blood. If it is determined that a medication is causing the tremor, the medication may be discontinued or another may be used in its place.

    What are the side effects of the treatments?

    Side effects depend on the treatments used. For example, diazepam may cause sleepiness. Dialysis has many side effects, including infections, salt imbalances, and death.

    What happens after treatment for the condition?

    Individuals with fatigue or drug-related trembling may be cured by treatment. These individuals can usually return to normal activities as soon as they feel able. Those with nervous system damage may be permanently disabled and need help with basic activities, such as eating or getting dressed.

    How is the condition monitored?

    An individual can usually monitor the trembling at home. Changes or responses to therapy can be reported to the healthcare provider. Other monitoring is related to the cause. For example, an individual with high thyroid hormone levels may need repeat thyroid function tests to make sure the level of thyroid hormone returns to normal after treatment.


    Author:Adam Brochert, MD
    Date Written:
    Editor:Slon, Stephanie, BA
    Edit Date:07/21/00
    Reviewer:Melissa Sanders, PharmD
    Date Reviewed:03/28/01


    The Merck Manual, 1995, Berkow et al.