Emergency warning signs, by body system.

This page is built for fast scanning. Each section names warning signs by body system, then ends with a "first 60 seconds" mini-list so you have something concrete to do while help is on the way. The single rule that overrides every list below: severe, sudden, or rapidly worsening means call now. These red flags do not change because the underlying cause is unfamiliar — see unknown pathogens and speculative preparedness for why the same escalation logic still applies even when the threat is novel.

Heart and circulation

• Chest pain, pressure, tightness, or squeezing, especially radiating to arm, jaw, neck, back, or stomach.
• Sudden severe shortness of breath, particularly with chest discomfort or cold sweat.
• Fainting, near-fainting, or unexplained collapse.
• New irregular heartbeat with dizziness or chest discomfort.
• One leg suddenly swollen, painful, and warm (possible blood clot).

What to do in the first 60 seconds

• Do: call 911. Sit or lie down. Loosen tight clothing. If aspirin is available and the person is conscious and not allergic, chew one regular adult tablet (325 mg) while waiting.
• Don't: drive yourself. Don't ignore symptoms because they ease briefly; cardiac pain comes and goes.

Brain and nervous system (FAST)

Use the FAST rule:

• Face drooping on one side.
• Arm weakness or numbness, often one-sided.
• Speech slurred, garbled, or hard to find words.
• Time: note when symptoms started and call 911 immediately.

Other neurological red flags:

• Sudden severe "thunderclap" headache, unlike any before.
• New confusion, trouble staying awake, or unusual personality change.
• Seizure, especially a first-ever seizure or one in pregnancy.
• Sudden vision loss, double vision, or severe vertigo.
• Sudden severe weakness or numbness, especially one-sided.

What to do in the first 60 seconds

• Do: call 911 and write down the exact time symptoms started. Have the person lie on their side if drowsy. Stay with them.
• Don't: give food, drink, or aspirin until paramedics evaluate. Treatment windows are measured in minutes.

Breathing

• Trouble breathing at rest, or unable to speak in full sentences.
• Blue lips, blue fingertips, or pale-gray skin tone.
• Severe wheezing, stridor (high-pitched breathing), or a feeling that the throat is closing.
• Coughing up blood.
• Chest pain with breathing, especially after a long flight, recent surgery, or extended immobility.

What to do in the first 60 seconds

• Do: call 911. Sit the person upright, slightly leaning forward. Use a prescribed rescue inhaler if they have one.
• Don't: lay them flat or insist on water if they are struggling to breathe.

Severe allergic reaction (anaphylaxis)

• Throat tightness, difficulty swallowing, hoarse voice.
• Lip, tongue, or face swelling.
• Hives or widespread rash with breathing trouble or dizziness.
• Sudden vomiting plus rash plus weakness after a known allergen.

What to do in the first 60 seconds

• Do: use an epinephrine auto-injector if available, then call 911 even if symptoms ease. Lay the person flat with legs raised unless they are vomiting or struggling to breathe.
• Don't: assume one dose is enough; symptoms can rebound.

Bleeding and trauma

• Bleeding that does not slow with firm direct pressure for 10 minutes.
• Vomiting blood, or vomit that looks like coffee grounds.
• Black, tarry, or bright-red stools.
• Significant head injury, especially with vomiting, confusion, or loss of consciousness.
• Possible broken bone with deformity, severe pain, or numbness.
• Deep wound, animal bite, or burn larger than the palm or affecting face, hands, or joints.

What to do in the first 60 seconds

• Do: call 911 for serious bleeding. Apply firm continuous pressure with the cleanest cloth on hand. Elevate the limb if possible.
• Don't: peek under the dressing every minute (it disturbs clotting) or remove an embedded object; pad around it.

Abdominal symptoms

• Severe abdominal pain, especially in the lower right or upper right side.
• Pain plus fever plus persistent vomiting plus inability to keep fluids down.
• Sudden severe pain in someone who recently had abdominal surgery.
• Rigid, board-like abdomen.
• Dehydration signs: very little urination, dark urine, dizziness on standing.

What to do in the first 60 seconds

• Do: call your clinician or 911 depending on severity. Note when pain started, where it sits, and whether it moves. Keep the person still.
• Don't: give food or pain medication until evaluated.

Pregnancy

• Heavy vaginal bleeding or passing tissue.
• Severe abdominal or pelvic pain.
• Severe headache, vision changes, or sudden swelling (possible preeclampsia).
• Decreased or absent fetal movement past viability.
• Leaking fluid, regular contractions before 37 weeks.
• Fever at or above 100.4°F (38°C) at any point in pregnancy.

What to do in the first 60 seconds

• Do: call your obstetric provider immediately, or 911 for heavy bleeding, severe pain, fainting, or seizure. Lie on your left side.
• Don't: wait to "see if it settles" or drive yourself if bleeding heavily or feeling faint.

Infants and young children

• Any rectal temperature at or above 100.4°F (38°C) in an infant under 3 months.
• Lethargy: hard to wake, not engaging, very limp.
• Rapid breathing, ribs visibly pulling in with each breath, or bluish color.
• Persistent inability to keep down fluids, or no wet diaper for 8 or more hours.
• Stiff neck, bulging soft spot, or a rash that does not fade when pressed.
• Seizure, especially a first-ever one.

What to do in the first 60 seconds

• Do: call 911 or your pediatric line. Keep the child upright if they are breathing fast. Note last feed, last wet diaper, and any medication given.
• Don't: bundle in heavy blankets if feverish or give honey to infants under one.

Mental health crisis

• Suicidal thoughts with a plan, or active intent to harm yourself or others.
• Severe psychotic symptoms or sudden inability to function safely.

In the U.S., dial or text 988 for the Suicide and Crisis Lifeline. Call 911 if there is immediate danger. Outside the U.S., contact your local crisis line or emergency number.

What to do in the first 60 seconds

• Do: stay with the person. Listen without judgment. Remove access to firearms or large medication supplies.
• Don't: argue, lecture, or promise to keep dangerous thoughts secret.

Poisoning, overdose, or environmental

• Suspected overdose, accidental ingestion, or unknown chemical exposure.
• Carbon monoxide concern: headache, dizziness, nausea in multiple people in the same building.
• Heat stroke: hot, dry skin, confusion, very high body temperature.
• Severe hypothermia: shivering stopped, confusion, slurred speech, slow breathing.

In the U.S., the Poison Control hotline is 1-800-222-1222, available 24 hours. Call 911 if the person is unresponsive, having a seizure, or struggling to breathe.

What to do in the first 60 seconds

• Do: bring the bottle, package, or substance with you (or photograph the label). For carbon monoxide, get everyone outside and call 911. Give naloxone for suspected opioid overdose.
• Don't: induce vomiting unless told to by Poison Control.

After you call: what to tell the dispatcher

Stay on the line. The dispatcher will guide you. Lead with the essentials:

• Your exact location, with apartment number and gate code.
• What is happening, in one sentence: "Adult, mid-50s, chest pain and sweating for 20 minutes."
• Whether the person is conscious and breathing.
• Time symptoms started.
• Known conditions, allergies, and recent medications.
• If a defibrillator, naloxone, or epinephrine auto-injector is on scene.

Educational reference only. See Medical Disclaimer. For an active emergency, call 911 (U.S.) or your local emergency number; do not rely on this page in place of a clinician.