FAST does not capture every possible stroke symptom — it will not flag a sudden severe headache or a sudden loss of coordination on its own. But it provides a fast, reliable check for three of the most visible and common signs.
The underlying principle is captured in a phrase physicians use: “Time is brain.” When blood flow to the brain is cut off, brain cells begin to suffer. The longer the disruption continues, the greater the potential for permanent damage.
What to do — and what not to do — in the first minutes
The first and most important action is to call emergency medical services rather than driving the person to the hospital. Emergency personnel can begin assessment and care during transport and alert the receiving hospital, saving valuable minutes.
Note the exact time symptoms were first noticed, or the last time the person was known to be completely normal. This information directly influences treatment decisions, because some stroke treatments are highly time-sensitive.
Two common instincts can cause harm. Do not give food, water, or medication by mouth — stroke can impair swallowing, and anything given orally can enter the lungs instead of the stomach. Do not give aspirin unless a medical professional specifically instructs it. Aspirin could worsen bleeding in a hemorrhagic stroke, and brain imaging is typically needed to determine the stroke type before certain treatments are started.
If the person is unconscious but breathing, follow emergency-dispatch instructions. If they are not breathing normally, contact emergency services immediately and begin CPR if you are trained to do so.
