Explainer
Stroke warning signs: what to look for and what to do
The key sign of a stroke is that symptoms start suddenly. If you see one, call 911 at once, even if it goes away. Here are the signs as the National Institutes of Health lists them, the F.A.S.T. test, and how stroke risk can be lowered.
The sudden warning signs
The National Institute of Neurological Disorders and Stroke (NINDS) says the key to recognizing a sign of stroke is that symptoms appear suddenly. It advises calling 9-1-1 at once if one or more of these appear suddenly (NINDS):
- Sudden numbness: numbness or weakness of the face, arm or leg, especially on one side of the body.
- Sudden confusion: trouble speaking, or trouble understanding speech.
- Sudden trouble seeing: in one or both eyes.
- Sudden trouble walking: dizziness, or loss of balance or coordination.
- Sudden severe headache: with no known cause.
MedlinePlus, from the National Library of Medicine, lists the same five signs (MedlinePlus). NINDS adds that, more rarely, people having a stroke may have disorientation or memory loss, drowsiness, double vision, nausea, dizziness or vomiting (NINDS). The National Heart, Lung, and Blood Institute (NHLBI) notes that the signs often come on quickly but can develop over hours or even days (NHLBI).
The F.A.S.T. test
If you think someone may be having a stroke, NINDS and NHLBI suggest this quick test (NINDS) (NHLBI):
| Letter | What to do |
|---|---|
| F: Face | Ask the person to smile. Does one side of the face droop? |
| A: Arms | Ask the person to raise both arms. Does one arm drift downward? |
| S: Speech | Ask the person to repeat a simple phrase. Is the speech slurred or strange? |
| T: Time | If you see any of these signs, call 9-1-1 right away. |
The test does not cover every sign. Sudden trouble seeing, sudden trouble walking or a sudden severe headache are also reasons to call 911 (NINDS) (MedlinePlus).
Why to call 911 at once
During a stroke, brain cells cannot get the oxygen and nutrients they need and start to die within a few minutes. MedlinePlus says immediate treatment may save someone's life and increase the chances of a good recovery, and that every minute counts (MedlinePlus).
- Treatment has a time window. NINDS says the best stroke treatments can only be used within four and a half hours of the first symptoms. Some people benefit from treatment up to 24 hours after a stroke, so anyone who suspects a stroke, including people who wake up with symptoms, should get to the hospital as soon as possible (NINDS).
- Note the time. Write down or remember when the first symptoms started. NINDS says this helps doctors decide on the best treatment (NINDS).
- Take an ambulance. A person having a stroke should not drive or be driven. An ambulance lets the crew begin treatment on the way (NINDS) (NHLBI).
- Bystanders matter. A person having a stroke may not realize it, may ignore the signs, or may not be able to call for help. NINDS says they have the best chance of recovery if someone nearby recognizes the signs and acts fast (NINDS).
Signs that go away: TIA
A transient ischemic attack (TIA), often called a mini-stroke, happens when the blood supply to part of the brain is briefly blocked. Its symptoms are like those of a stroke. Most go away within an hour, although they may last for up to 24 hours (MedlinePlus) (NINDS).
You cannot tell whether symptoms are from a TIA or a stroke, so MedlinePlus says to go to the hospital right away (MedlinePlus). NINDS says to call an ambulance and not try to drive (NINDS). NINDS also warns that many people ignore a TIA because it clears up, and that about one-third of people who have a TIA will have a severe stroke sometime in the future (NINDS) (NINDS). After a TIA, clinicians may use the ABCD2 score to estimate the short-term stroke risk.
How stroke risk can be lowered
MedlinePlus names high blood pressure as the primary risk factor for stroke. Its other major risk factors are diabetes, heart diseases such as atrial fibrillation, smoking, a personal or family history of stroke or TIA, older age, and race and ethnicity (MedlinePlus). NINDS says many strokes can be prevented by treating risk factors and by taking a TIA seriously as a warning sign (NINDS).
MedlinePlus lists these heart-healthy changes for people who have had a stroke or are at risk of one: eating a heart-healthy diet, aiming for a healthy weight, managing stress, getting regular physical activity, quitting smoking, and managing blood pressure and cholesterol. If these are not enough, medicine may be needed (MedlinePlus). NINDS adds cutting back on alcohol (NINDS).
Tools on this site that look at these risk factors:
- Stroke risk factor check: which CDC stroke risk factors apply to you.
- Blood pressure ranges: what your reading means.
- Atrial fibrillation screening check: what screening advice says about AFib.
- CHA2DS2-VASc explained: the stroke risk score doctors use for people who already have AFib.
Common questions
Should I wait to see if the symptoms go away?
No. NINDS says to call 9-1-1 the moment you see any of the signs, and not to ignore symptoms that go away quickly, because they may be a TIA (NINDS).
Can a calculator tell me whether I am having a stroke?
No. No online tool can rule a stroke in or out. The scores on this site, such as the ABCD2 score, are for clinicians or for long-term risk, not for deciding whether to call 911.
What is B.E. F.A.S.T.?
It is a longer version that adds Balance loss and Eye changes to F.A.S.T. (CDC). Both point to the same action: call 911.
Sources
- National Institute of Neurological Disorders and Stroke (NIH). Stroke: Signs and Symptoms. Reviewed July 23, 2026. www.ninds.nih.gov/health-information/stroke/signs-and-symptoms
- National Heart, Lung, and Blood Institute (NIH). Stroke: Symptoms. Last updated May 26, 2023. www.nhlbi.nih.gov/health/stroke/symptoms
- MedlinePlus (National Library of Medicine). Stroke. Last updated July 28, 2025. medlineplus.gov/stroke.html
- MedlinePlus (National Library of Medicine). Transient Ischemic Attack. Last updated November 19, 2025. medlineplus.gov/transientischemicattack.html
- National Institute of Neurological Disorders and Stroke (NIH). Transient Ischemic Attack (TIA). www.ninds.nih.gov/health-information/disorders/transient-ischemic-attack
- Centers for Disease Control and Prevention. Signs and Symptoms of Stroke. www.cdc.gov/stroke/signs-symptoms/index.html
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-11-05. Spotted an error? See About.