Stroke is known as the illness that “strikes out of nowhere”, but in reality the body often signals first. The trouble is that those signals can vanish within minutes, so people shrug them off as tiredness.
1. Is this an emergency right now. One F.A.S.T. sign is enough — the CDC writes “if you see any of these signs, call immediately.” You do not need all four.
2. The most dangerous moment. When the symptoms stop. They can vanish in minutes and get written off as tiredness — but 17% of people who have a transient ischaemic attack (TIA) go on to have a stroke. Go anyway.
3. How you get there. Do not drive. The CDC states: “Do not drive to the hospital or let someone else drive you. Call an ambulance” — treatment starts in the ambulance. Note too that the “4.5-hour golden window” widely quoted in Korea does not match the figure the CDC prints.
If you suspect symptoms right now, stop reading and call emergency services (119 in Korea, 9-1-1 in the US). The CDC states: “Do not drive to the hospital or let someone else drive you. Call 9-1-1 for an ambulance.”
What do you look for
English-speaking countries teach F.A.S.T. Korea teaches 이웃손발시선 (i-ut-son-bal-si-seon). They point at almost the same signs.
| F.A.S.T. | How the CDC says to check | Korean equivalent |
|---|---|---|
| Face | “Ask the person to smile. Does one side of the face droop?” | 이~웃 — one corner of the mouth droops on smiling |
| Arms | “Ask the person to raise both arms. Does one arm drift downward?” | 손 (hand) — one arm drops |
| Speech | “Ask the person to repeat a simple phrase. Is the speech slurred or strange?” | 발 (speech) — slurred words |
| Time | “If you see any of these signs, call 9-1-1 right away.” | 시선 (gaze) — the gaze pulls to one side, or half the visual field goes |
Learning either one is enough. Note only that the T in F.A.S.T. is time, not a symptom — the Korean version uses that slot for a fourth sign, the visual one.
How long is the golden window
The number usually quoted in Korea is 4.5 hours. The CDC's stroke treatment page says this:
“If you get to the hospital within 3 hours of the first symptoms of an ischemic stroke, you may get a type of medicine called a thrombolytic.”
— US Centers for Disease Control and Prevention, stroke treatment page (last reviewed 14 May 2024)
The thrombolytic window is generally understood as three hours as standard, extended for some patients who meet additional criteria. But we could not find a public-agency page stating 4.5 hours. So here is the honest version.
- What is certain — the CDC original says three hours, and it says “brain cells begin to die within minutes” without oxygen.
- What matters more — whether it is three hours or four and a half, your action is identical. Not timing it, but calling for an ambulance now. In the CDC's words, “the key to stroke treatment and recovery is getting to the hospital quickly.”
- The one thing to record — when the symptoms started. It determines which treatment is possible. “Around 3:20 pm” helps far more than “I'm not sure when.”
What if the symptoms go away
Symptoms that appear and then fade on their own within minutes or hours are a transient ischemic attack — a TIA, or “mini stroke”. The CDC describes it as blood flow being blocked “for a short time — usually no more than five minutes”.
It is easy to feel relieved and move on. Here is the number the CDC attaches to that relief:
“The risk of stroke within 90 days of a transient ischemic attack (TIA) may be as high as 17%, with the greatest risk during the first week.”
— US Centers for Disease Control and Prevention, stroke treatment page
That is roughly one in six. And the risk is concentrated not in what already happened but in the week ahead. See a doctor even if the symptoms have gone. “But I feel fine now” is the most expensive judgement in this article.
The other signs to watch
These are the five the CDC lists. Every one of them begins with the word “sudden”.
- Sudden numbness or weakness in the face, arm, or leg — especially on one side of the body
- Sudden confusion, trouble speaking, or difficulty understanding speech
- Sudden trouble seeing
- Sudden trouble walking, dizziness, loss of balance, or lack of coordination
- Sudden severe headache with no known cause
Seoul's health notice carries almost the same list and adds “seeing double”, “unable to read or write” and “reduced consciousness”. Its phrase for the headache — “a sudden headache like a thunderbolt” — is worth remembering.
What do you do right now
| Do | Do not |
|---|---|
| Call an ambulance immediately — it goes straight to a hospital equipped for stroke | Drive to the hospital, or let someone else drive you (the CDC says this explicitly) |
| Write down when the symptoms started | Wait and “see how it goes” |
| Lay the person flat and loosen ties and belts | Give food or drink — swallowing may be impaired |
| Tell the paramedics about medications and medical history | Folk remedies such as pricking fingertips — they only cost time |
For deciding whether other situations need an emergency room, see ER or clinic; for an unconscious person, CPR and choking first aid. Other household emergencies are covered here.
Which risks can you change
The CDC splits risk factors into two groups.
| Can be changed | Cannot be changed |
|---|---|
| High blood pressure · high cholesterol · heart disease · diabetes · obesity | Age — risk roughly doubles every decade after 55 |
| A diet high in saturated fat, trans fat and cholesterol; too much salt | Sex — the CDC notes stroke is more common in women, with higher mortality |
| Physical inactivity | Race and ethnicity |
| Drinking too much — more than one drink a day for women, two for men | A previous stroke or TIA · family history · sickle cell disease |
| Smoking and secondhand smoke exposure |
Being young is not the same as being safe. The CDC states that about one in seven strokes occurs in people aged 15 to 49. Age raises the risk; it does not exempt anyone.
Almost everything in the left-hand column shows up in a routine health check. How to read those results is covered in reading your check-up report, and borderline blood sugar in the prediabetes guide. If you take several medications, see managing multiple prescriptions.
Questions this raises
Is dizziness alone a stroke?
Dizziness has many causes. But in the CDC's list it appears bundled with “sudden trouble walking, loss of balance, or lack of coordination” — and if slurred speech or one-sided weakness appears with it, call for an ambulance immediately.
The symptoms cleared up in five minutes. Do I still need to be seen?
Yes. That may be exactly what a TIA is, and the CDC puts the following 90-day stroke risk at up to 17%, greatest in the first week. Symptoms that vanish are a warning, not an all-clear.
It started while I was asleep and I don't know when.
Report the last time you were known to be well. If you were fine going to bed, that is the reference point.
Does it happen to young people?
It does. The CDC states that about one in seven strokes occurs between 15 and 49. If you have high blood pressure or smoke, age offers no protection.
Sources
- US Centers for Disease Control and Prevention — Signs and Symptoms of Stroke (last reviewed 19 May 2026). Source of the F.A.S.T. checks as worded, the five “sudden” symptoms, and “Do not drive to the hospital or let someone else drive you. Call 9-1-1 for an ambulance.”
- US Centers for Disease Control and Prevention — Treatment and Intervention for Stroke (last reviewed 14 May 2024). Source of the three-hour thrombolytic window, “the key to stroke treatment and recovery is getting to the hospital quickly”, and the 17% / 90-day / first-week TIA figures.
- US Centers for Disease Control and Prevention — Risk Factors for Stroke (last reviewed 15 May 2024). Source of the changeable / unchangeable split, risk roughly doubling each decade after 55, about one in seven strokes at ages 15–49, and the drinking thresholds.
- US Centers for Disease Control and Prevention — About Stroke (last reviewed 24 October 2024). Source of the ischemic / hemorrhagic / TIA distinction and of “brain cells begin to die within minutes”.
- Seoul Metropolitan Government — stroke warning signs notice (19 June 2026). Source of the Korean symptom list (including seeing double, inability to read or write, and reduced consciousness) and of the instruction to call 119 and reach an emergency room within the golden window.
Where to check further
- A public-agency source for the “4.5-hour golden window”. It is widely used in Korea but we could not find that sentence on a public-agency page, and the CDC prints three hours — both are set out in the article. The Korean Stroke Society and the KDCA health information portal carry the Korean position.
- The original wording of the Korean mnemonic. The Korean column is written as the phrasing in common use; only the CDC's F.A.S.T. was checked word for word — the Korean Stroke Society publishes the original.
- Korean stroke statistics. We could not verify the Seoul notice's “over 30% of deaths”, so it is not in the article — Statistics Korea's causes-of-death data and the KDCA publish the annual figures.
Written as of July 2026. The F.A.S.T. checks, the symptom list, the three-hour figure, the 17% TIA risk and the risk-factor split all come from the CDC pages above; the Korean symptom list and the instruction to call 119 come from Seoul's notice. This is general health information and does not replace medical diagnosis or treatment. If you suspect symptoms, call emergency services without delay.
