Syncope
Most fainting is harmless, but the warning pattern matters
General information from an emergency physician. It adds to your discharge papers and does not replace them or your own doctor. What this site is and isn’t
Key Takeaways:
- Syncope means briefly passing out because too little blood reached the brain.
- If warmth, sweating, nausea, or dimming vision warns you first, lie flat. Muscle squeezing can help push pooled blood back toward the heart.
- Fainting during exercise, while lying down, or without warning needs urgent reassessment.
About Your Diagnosis and ED Workup
Syncope is a brief loss of consciousness caused by a drop in blood flow to the brain. It is not the same as a seizure or heart attack. Brief jerking can happen during a faint and may look like a seizure.
The common vasovagal faint is a reflex. Blood pools in the lower body, blood pressure falls, and the brain briefly receives too little flow. Lying flat removes the pull of gravity, restores flow, and is why consciousness often returns quickly.
Most faints are reflex or posture-related. A smaller group comes from a heart rhythm or heart structure problem. Across ED syncope patients, about one in ten has a serious condition found within 30 days.
An ECG is a short recording of the heart’s electrical rhythm. It can find important clues, but it is only a snapshot. A normal ED evaluation cannot exclude a rhythm problem that comes and goes.
Doctors may use the Canadian Syncope Risk Score to estimate 30-day risk. It combines nine clinical details and test findings. It is information for clinicians, not a score to use for self-diagnosis.
First Steps and Evidence-Based Home Care
1. Act during the warning phase
Warmth, sweating, nausea, pale skin, dimming vision, or muffled hearing can occur before a reflex faint. These signs often provide a short window to act. Lie flat and raise your legs. Do not remain propped upright in a chair.
If you have enough warning and your clinician has said the spells are reflex faints, cross your legs and squeeze the leg, belly, or arm muscles hard. Squatting can also help. These actions push pooled blood toward the heart and raise pressure. They are not a treatment for a heart-caused faint.
2. Follow the fluid and salt plan given to you
Hydration and added salt can help recurrent vasovagal fainting, but extra salt is not appropriate for everyone, including some people with high blood pressure or heart failure. Use the plan from your own care team rather than choosing an amount from this page.
3. Review triggers and medicines
Pain, strong emotion, blood draws, and hot or crowded rooms can trigger a reflex faint. Dehydration and some medicines can contribute to posture-related fainting. Write down the setting, warning signs, and medicines taken that day for follow-up.
Timeline and Expected Recovery Course
A reflex faint usually corrects after the person becomes horizontal and brain blood flow returns. Reflex syncope does not increase long-term mortality compared with people who have not fainted.
That reassurance does not apply to every cause. Three to five percent of ED syncope patients have a serious condition found only after discharge. Among medium- and high-risk patients, most later rhythm events appear within 15 days, which supports outpatient rhythm monitoring in selected patients.
Faints can also recur. Hydration, trigger changes, medicine review, and counterpressure maneuvers can reduce recurrent vasovagal episodes, but they do not correct a heart rhythm or structural heart problem.
Emergency Red Flags: Return Immediately
Return to the emergency department for any of these:
- Fainting during exercise or while lying down.
- A sudden faint with no warning.
- Chest pain, trouble breathing, or a racing or irregular heartbeat with the faint.
- Several faints close together.
- New weakness, numbness, trouble speaking, or confusion that lasts after waking.
- A close family history of sudden cardiac death, especially before age 50.
This list does not cover everything. Return to the emergency department if several faints happen close together or something feels seriously wrong.
Reviewed September 3, 2026