Restless leg syndrome (RLS) is diagnosed primarily through a clinical interview, not a single test or scan. There is no blood test, imaging study, or sleep study that confirms it on its own. Instead, your doctor will ask detailed questions about your symptoms, check for underlying conditions that could be causing them, and rule out other problems that can mimic RLS.
The Five Core Diagnostic Criteria
A diagnosis of RLS requires all five of the following features to be present:
- An urge to move the legs, usually accompanied by uncomfortable or unpleasant sensations in the legs.
- Symptoms begin or worsen during rest or inactivity, such as lying down or sitting.
- Movement partially or totally relieves the urge, at least while you keep moving.
- Symptoms are worse in the evening or at night compared to daytime, or occur only at night.
- Symptoms are not better explained by another condition, such as leg cramps, poor circulation, or nerve damage.
If you meet all five, a doctor can make the diagnosis in that visit. No further testing is needed to confirm RLS itself. The additional steps in the process are about finding what’s driving it and measuring how severe it is.
What the Physical Exam Looks For
The physical exam in someone with RLS is typically normal, which is actually part of the point. Your doctor performs it to identify secondary causes and rule out conditions that look similar. The exam focuses on two systems in particular: neurological and vascular.
On the neurological side, the doctor checks for signs of peripheral neuropathy (nerve damage in the hands and feet), radiculopathy (pinched spinal nerves), and parkinsonism. These involve testing reflexes, sensation, muscle strength, and coordination. If neuropathy is found, it doesn’t necessarily rule out RLS, since the two conditions can coexist, but neuropathic symptoms differ in that they don’t improve with movement and don’t follow a clear evening or nighttime pattern.
The vascular exam checks for peripheral pulses, swelling, and skin temperature in the legs. Vascular disease, including deep vein thrombosis and poor arterial circulation, can cause leg discomfort, but it typically worsens with activity rather than rest and doesn’t follow a time-of-day pattern. People with RLS have normal pulses and don’t have the cool, swollen extremities that signal vascular problems.
Blood Tests and Iron Levels
Blood work is a standard part of the diagnostic workup, not to confirm RLS but to identify treatable causes behind it. The most important test is serum ferritin, which reflects your body’s iron stores. Low brain iron is now recognized as a major underlying driver of RLS, and recent clinical guidelines from the American Academy of Sleep Medicine elevate iron evaluation as a priority for every patient diagnosed with the condition.
The threshold that matters is different from what’s considered “normal” on a standard lab report. While a general lab might flag ferritin as low only when it drops below 15 or 20 ng/mL, RLS experts recommend treatment when ferritin is at or below 75 ng/mL with transferrin saturation (a measure of how much iron is available in the blood) below 45%. If your ferritin falls below the lower limit of normal for your age and sex, your doctor should also investigate why your iron is low in the first place.
Additional blood tests typically screen for kidney disease and diabetes, both of which are known secondary causes of RLS. Kidney disease in particular, especially in its advanced stages, is strongly associated with RLS symptoms.
Conditions That Mimic RLS
Part of the diagnostic process is making sure your symptoms aren’t caused by something else entirely. Several conditions overlap enough with RLS to cause confusion.
Nocturnal leg cramps are the most common look-alike. Like RLS, they strike at rest and often follow a nighttime pattern. But cramps involve a sudden, painful, involuntary muscle contraction you can physically feel as a hard knot in the muscle. RLS doesn’t produce that kind of visible, palpable muscle tightening. Cramps also tend to affect one leg at a time, while RLS symptoms are usually bilateral.
Peripheral neuropathy causes burning, tingling, or numbness that can be confused with the uncomfortable sensations of RLS. The key differences: neuropathy symptoms don’t come with the restless urge to move, aren’t relieved by walking around, and don’t peak in the evening.
Painful legs and moving toes is a rarer condition involving involuntary flexion and extension of the toes, usually linked to spinal cord injury or nerve root damage. It lacks the characteristic urge to move and doesn’t follow a circadian pattern.
Vascular disease, whether from poor arterial flow or venous insufficiency, causes leg discomfort that worsens with walking or standing, the opposite of RLS. The physical exam findings (weak pulses, swelling, cool skin) make this relatively straightforward to distinguish.
When a Sleep Study Is Needed
Polysomnography, the overnight sleep study most people associate with sleep disorders, is not a standard part of RLS diagnosis. The American Academy of Family Physicians specifically advises against using it for this purpose in most cases. RLS is a clinical diagnosis made from your symptom history.
The exception is when the clinical picture is unclear. If your symptoms don’t neatly fit the five diagnostic criteria, or if your doctor suspects another sleep disorder is at play, a sleep study can document periodic limb movements during sleep. These repetitive leg jerks occur in about 80% of people with RLS and can support the diagnosis when the history alone is ambiguous. But for most people, the sleep study adds cost and inconvenience without changing the outcome.
How Severity Is Measured
Once RLS is diagnosed, your doctor may use a standardized questionnaire to gauge how much it’s affecting your life. The most widely used tool is a 10-item rating scale developed by the International Restless Legs Syndrome Study Group. It asks about the intensity of your sensations, how often symptoms occur, how much they disrupt your sleep, and how they affect your mood and daily functioning.
Scores range from 0 to 40:
- Mild: 1 to 10 points
- Moderate: 11 to 20 points
- Severe: 21 to 30 points
- Very severe: 31 to 40 points
This score helps guide treatment decisions. Someone with mild, occasional symptoms may only need lifestyle changes and iron supplementation, while someone scoring in the severe range will likely need more targeted therapy. The scale is also useful for tracking whether treatment is working over time.
Diagnosing RLS in Children
Children can develop RLS, but diagnosis is trickier because younger kids struggle to describe the sensations accurately. The International Restless Legs Syndrome Study Group developed pediatric-specific guidance that uses the same core criteria as adults but accounts for the way children communicate. A child might say their legs feel “creepy-crawly,” “wiggly,” or “like they need to run,” rather than using the adult language of discomfort or restlessness.
Children must be able to describe the leg sensations in their own words for a diagnosis to be made. A parent’s observation alone isn’t sufficient, because many childhood conditions (growing pains, hyperactivity, bedtime resistance) can look similar from the outside. Iron evaluation is especially important in pediatric cases, as ferrous sulfate is currently the only treatment with a formal recommendation for children with RLS.
Screening for Secondary Causes
RLS can be either primary (genetic, with no identifiable trigger) or secondary (caused or worsened by another condition). The diagnostic process includes screening for the most common secondary causes so they can be addressed directly.
Beyond iron deficiency and kidney disease, pregnancy is a well-known trigger. RLS affects a significant portion of pregnant women, particularly in the third trimester, and typically resolves after delivery. Diabetes is another common contributor, partly because it frequently causes peripheral neuropathy that can overlap with or worsen RLS.
Certain medications can also trigger or aggravate symptoms. Antihistamines, some antidepressants, and anti-nausea drugs are among the most frequent culprits. Your doctor will review your medication list as part of the evaluation. Identifying and addressing a secondary cause sometimes resolves RLS entirely, making this step one of the most practically important parts of the diagnostic process.