Your doctor will diagnose RLS based on how you describe your symptoms. It's important to keep track of when symptoms occur and what makes them better or worse, as well as any other sleep problems you are having.
There is no blood test for RLS. However, low iron stores are thought to cause or aggravate RLS in some people. Your doctor may want to check your iron stores using a serum ferritin test or test for other conditions such as kidney disease or vitamin deficiencies that could be causing your RLS.
A sleep study is required to diagnose some sleep disorders but is not necessary for the diagnosis of RLS. However, your doctor may want a sleep study to check whether you have periodic limb movements during sleep. Your doctor may also recommend other tests to determine whether nerve damage is to blame for your RLS.
A sleep study, also called a polysomnogram, is a painless, noninvasive test that records your physical state during various stages of sleep. While a polysomnogram is not necessary for the diagnosis of RLS, your doctor may have you undergo a sleepy study to check for periodic limb movements, in which the limbs move involuntarily while you are asleep. (Most people with RLS also have periodic limb movements, although the reverse is not true.) It provides data that are essential in evaluating sleep and sleep-related complaints and problems, such as identifying sleep stages, brain waves, eye movement, muscle tone, body position, blood oxygen levels, breathing events, snoring, heart rate, and general sleep behavior.
Sleep studies are performed in a sleep laboratory that is specially equipped with computerized monitoring equipment. Most sleep studies take place at night. After you change into your nightclothes, the technician will connect you to a number of electrodes that will record your brain waves and muscle movements throughout the night. A microphone will record snoring, and two belt-like straps around the chest and lower abdomen will monitor chest and abdominal movements during breathing. Despite all of the equipment, most people say their sleep is not disrupted. After the technician is certain that electrodes are recording properly, the lights will be turned off and you can go to sleep. You will be able to talk to the technician, who will constantly monitor your test from an adjoining room. The technician will also help you if you need to use the restroom during the night.
You will be awakened in the morning, the electrodes will be removed, and you may shower and dress. Since the electrodes are applied with water-soluble glue or tape, removal is not painful. You will be asked to complete a questionnaire about your sleep the previous night, and then you can go home.
Your physician will explain the results to you and talk with you about follow-up treatment, if required.