The stroke test most people search for is BE FAST, a simple checklist that helps bystanders recognize stroke symptoms in real time. Each letter stands for a warning sign: Balance loss, Eye changes, Face drooping, Arm weakness, Speech difficulty, and Time to call 911. If someone shows even one of these signs, calling emergency services immediately gives them the best chance of recovery.
The BE FAST Test, Step by Step
You don’t need medical training to perform this test. It takes less than a minute, and you can do it anywhere. Here’s what to check:
- B, Balance: Is the person suddenly unsteady, dizzy, or unable to walk straight? A stroke can knock out the brain’s coordination centers without warning.
- E, Eyes: Ask if they’ve lost vision in one or both eyes, or if they’re seeing double. Sudden visual changes with no obvious cause are a red flag.
- F, Face: Ask the person to smile. If one side of their face droops or doesn’t move, that suggests the brain isn’t sending normal signals to the facial muscles.
- A, Arms: Ask them to raise both arms and hold them up. If one arm drifts downward or they can’t lift it at all, that’s a sign of one-sided weakness, one of the most reliable stroke indicators.
- S, Speech: Ask them to repeat a simple sentence. Slurred words, jumbled speech, or an inability to speak points to a stroke affecting the brain’s language areas.
- T, Time: If any of the above are present, call 911 immediately. Note the time symptoms started, because treatment options depend on how much time has passed.
Why BE FAST Replaced the Older FAST Test
For years, public health campaigns used a shorter version called FAST, which only covered face, arms, speech, and time. It missed balance and vision problems entirely. That matters because strokes in the back of the brain often cause dizziness and visual disturbances rather than the classic arm weakness or facial droop. A meta-analysis of nine studies with over 6,000 participants found that the original FAST caught about 77% of strokes. BE FAST trades some of that raw sensitivity for better overall diagnostic accuracy, picking up posterior strokes that FAST would miss.
What Paramedics Check on the Way to the Hospital
Once emergency medical services arrive, they run their own rapid assessment. Many use a tool called the Cincinnati Prehospital Stroke Severity Scale, which checks three things: whether the eyes move together normally, whether both arms have equal strength, and whether the person can follow simple commands and answer basic questions. This helps paramedics estimate how severe the stroke is before reaching the hospital, so the right team and equipment are ready on arrival. A score of 2 or higher on this scale identifies a severe stroke with roughly 90% sensitivity.
Paramedics also check blood sugar. Low blood sugar can cause slurred speech, confusion, and one-sided weakness that looks almost identical to a stroke. Ruling that out takes seconds with a finger prick and can completely change what happens next.
Tests Performed at the Hospital
The first priority in the emergency department is brain imaging, typically a CT scan. This scan takes just a few minutes and answers the single most urgent question: is the brain bleeding? A stroke caused by a blood clot (ischemic) and one caused by a ruptured blood vessel (hemorrhagic) require opposite treatments, and there is no way to tell them apart from symptoms alone. Clot-busting medication given to someone with a brain bleed could be fatal, so imaging is mandatory before any treatment begins.
If the CT scan doesn’t show bleeding, doctors may follow up with an MRI. MRI with specialized sequences can detect areas of oxygen-starved brain tissue within minutes of a stroke’s onset. It pinpoints exactly where the damage is, how large the affected area is, and how much brain tissue might still be salvageable. This information helps the medical team decide whether more aggressive interventions are appropriate.
Blood tests run alongside imaging check for clotting function, electrolytes, kidney function, and blood cell counts. An EKG evaluates the heart, since irregular heart rhythms are one of the leading causes of clot-based strokes. These tests happen simultaneously rather than sequentially because every minute counts.
The NIH Stroke Scale
Doctors use a standardized scoring system called the NIH Stroke Scale to measure how severely the stroke has affected the brain. It tests roughly 15 different neurological functions: level of consciousness, ability to follow commands, eye movements, visual fields, facial movement, arm and leg strength, coordination, sensation, language, speech clarity, and awareness of surroundings. Each item receives a score, and the numbers add up to a total between 0 and 42.
A score of 0 to 5 indicates a minor stroke. Scores from 6 to 15 fall in the moderate range. Anything from 16 to 20 is moderate to severe, and 21 or above is a severe stroke. A score of 42, the maximum, typically means the person is in a coma. This scale gets repeated at regular intervals because it tracks whether the patient is improving or deteriorating, which directly shapes treatment decisions.
How Test Results Shape Treatment Timing
For ischemic strokes caused by a clot, the standard treatment window for clot-dissolving medication is 4.5 hours from when symptoms first appeared. That’s why the “T” in BE FAST emphasizes noting the exact time. If you were asleep when symptoms started and woke up with them, the clock starts from when you were last seen normal.
For larger clots blocking major blood vessels, a procedure to physically remove the clot can be performed up to 24 hours after symptoms began, but only if advanced imaging shows that enough brain tissue is still viable. This extended window was established by landmark trials published in 2018 that demonstrated clear benefits for carefully selected patients. Not everyone qualifies. The imaging has to show a mismatch between the area of brain already damaged and the larger area at risk, meaning there’s still tissue worth saving.
Conditions That Look Like a Stroke but Aren’t
About 31% of patients who arrive at the emergency department with suspected stroke turn out to have something else. The most common mimics include seizure aftereffects (which can cause temporary weakness on one side of the body), infections causing confusion, and metabolic problems like severely low blood sugar or electrolyte imbalances. Migraines with aura can also produce numbness, visual disturbances, and speech difficulty that closely resemble stroke symptoms.
One key difference is how symptoms begin. Stroke symptoms appear suddenly, all at once, and typically follow the pattern of a specific blood vessel’s territory in the brain. Migraine symptoms tend to build gradually and spread from one area to another over several minutes. That said, no single symptom can reliably rule a stroke in or out. The combination of a clear history of sudden focal neurological symptoms and a higher score on the NIH Stroke Scale are the strongest predictors of a true stroke. When in doubt, treat it as a stroke until imaging proves otherwise. The consequences of missing a real stroke far outweigh the inconvenience of a false alarm.