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Fainting (syncope)

Also called: Fainting, syncope, passing out, vasovagal syncope

A brief loss of consciousness from a drop in blood flow to the brain. Most fainting is harmless (from standing long, heat, pain, or the sight of blood), but fainting with exercise or chest symptoms can be from the heart.

Most commonVasovagal (common faint)
Warning signsLightheaded, sweaty, tunnel vision
Heart causesFainting during exercise or without warning

Overview

People usually wake within a minute.

Fainting while lying down, during exercise, or with a family history of sudden death needs a heart check.

Symptoms

Common signs:

  • Fainted or nearly fainted
  • Feeling faint or about to pass out

Less common

  • Lightheadedness
  • Sweating
  • Nausea
  • Pale skin

When to get medical care

Call 911Fainting during exercise, with chest pain, a racing heart, or a seizure, or not waking quickly: call 911.
Get care todayFirst faint in an older adult, or injury from the fall.
See a doctor soonFainting more than once.

Causes

Blood pressure drop, heart rhythm problems, dehydration.

Does it spread or run in families?

  • It isn't contagious. You can't catch it from someone else.
  • It can run in families. Tell your doctor if a parent, brother, or sister has it.

Who is more likely to get it

  • Teens
  • Older adults
  • Dehydration

Possible complications

Diagnosis

A clinician looks for the cause.

Questions you may be asked

  • What happened before
  • Heart symptoms, family history

The exam

Blood pressure lying and standing.

Tests

Tests, if needed:

  • ECG: Everyone who faints should have one.
  • Heart monitor or echo: If the heart could be the cause.

Treatment

Prevent faints.

Self-care

  • Lie down or sit with your head low when you feel faint
  • Drink plenty of fluids
  • Avoid standing still for long
  • Cross your legs and squeeze your muscles when you feel it coming

Prevention

To prevent fainting:

  • Stay hydrated
  • Stand up slowly

Which doctor treats this

  • Start with your primary care provider (family doctor or internist).
  • They may send you to a cardiologist (heart doctor) if fainting keeps happening.

Children, pregnancy, and older adults

  • Teens: Common faints are frequent and usually harmless.

Pregnancy and breastfeeding

  • If you're pregnant or planning to be, tell your prenatal provider about this condition.
  • Don't start or stop any medicine on your own. Some are safe in pregnancy and some need to be changed.
  • Ask before taking any pain reliever. The FDA advises avoiding ibuprofen and naproxen after 20 weeks unless your doctor says to.
  • Breastfeeding: Most medicines are fine, but ask. The NIH LactMed database lists what's known about each one.

Outlook

Most fainting is harmless.

Getting ready for your visit

Bring a list of your symptoms and medicines.

What to bring

  • A list of your medicines and supplements
  • Notes on when symptoms started and what makes them better or worse

Questions to ask

  • Do I need a heart test?

Research studies

Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.

Search ClinicalTrials.gov for studies on Fainting (syncope)

Sources

Last updated 2026-11-12.