When to Go to the ER After a Concussion
The SparkNotes
Most concussions do not need an emergency department. A small number of head injuries do, and the signs are specific enough to be worth knowing before you need them.
Severe or worsening headache, repeated vomiting, a seizure, loss of consciousness, deepening confusion, double vision, unequal pupils, weakness or numbness in more than one limb, slurred speech, agitation, or a visibly deformed skull all mean go now.
Getting worse over hours is itself a red flag. Bleeding inside the skull can take that long to announce itself.
Neck pain counts when the tenderness is midline over the bones and the neck will not turn 45 degrees to each side.
A blood thinner, age over 65, or a second head knock before the first had settled each lower the threshold on their own.
The Whole Story
Most people who take a knock to the head have a concussion and nothing worse, and a concussion is not an emergency department problem. It is managed over days and weeks, not in a waiting room.
But a small number of head injuries look exactly like a concussion in the first hour and are something else. Bleeding inside the skull. An injury to the bones of the neck. Those are uncommon. They are also the reason this page exists, because the cost of missing one is not measured in a slower recovery.
None of the signs below are subtle once you know to look for them.
The signs that mean go now
Any one of these is enough on its own. You do not need two.
Severe or increasing headache
Repeated vomiting
A seizure or convulsion
Loss of consciousness
Deteriorating conscious state, meaning not fully alert or oriented, or getting less so
Double vision
One pupil larger than the other
Weakness, numbness, or tingling and burning in more than one arm or in the legs
Increasingly restless, agitated, or combative
Slurred speech, or not recognizing familiar people or places
Visible deformity of the skull
Neck pain or tenderness, with the qualification further down this page
Call 911 rather than driving if there has been a seizure, if consciousness is lost or fading, if the neck is a concern, or if the person cannot be moved safely.
Worse over hours is its own warning
This is the one that catches people out.
Someone can be knocked out briefly, wake up, seem entirely normal for an hour or two, hold a conversation, and then deteriorate fast. That clear stretch in the middle is called a lucid interval, and it is the classic pattern for bleeding between the skull and the brain. The blood collects slowly and there is room for it, until there is not.
So he seemed fine at the time is not reassurance. What matters is the direction of travel. A headache worse than it was an hour ago. Confusion deeper than it was. Drowsiness that is harder to rouse someone from. Any of those, on their own, mean go.
Someone with a head injury should not be left alone to sleep it off in the first several hours unless someone qualified has said that is fine.
The neck is a separate question
Neck pain after a head injury gets treated casually because it is so common, and most of the time it is muscular and it settles. The concern is narrower than that, and it is worth knowing exactly how narrow.
Emergency departments use a decision tool called the Canadian C-Spine Rule to work out who needs the neck imaged. Two findings together are what matter. The tenderness sits midline, directly over the bones of the spine, rather than in the muscle to either side. And the person cannot actively turn their head 45 degrees to the left and to the right. Tenderness in the muscle with a neck that rotates freely is a different finding entirely.
The same rule sends three groups for imaging regardless of how the neck itself feels:
Anyone 65 or older
Anyone with pins and needles, numbness, or burning in the arms or legs
Anyone whose injury involved a dangerous mechanism
Dangerous mechanism has a specific meaning here: a fall from more than three feet or five stairs, an axial load through the top of the head such as a dive or a spear tackle, a high-speed collision, a rollover or an ejection, or a bicycle collision.
Worth holding onto for later. Once the neck has been cleared, neck pain flips from being a warning sign to being one of the most treatable causes of symptoms people assume belong to the brain. Same symptom, different clock, completely different answer. What Changed About Concussion Since You Last Heard
Three situations that lower the threshold
These do not depend on any symptom being present.
A BLOOD THINNER. Anticoagulant and antiplatelet medication mean a bleed that would have stopped on its own may not. The injury does not have to look dramatic for this to matter.
AGE OVER 65. The brain sits slightly looser inside an older skull, and the small veins crossing that space tear more easily, so a fall that looks minor can produce a bleed that declares itself slowly. Being over 65 is also an automatic trigger for imaging the neck.
A SECOND HEAD KNOCK BEFORE THE FIRST HAD SETTLED. A brain still recovering does not tolerate a second insult the way a rested one does. If someone is still symptomatic from a concussion and takes another, that is not a repeat of the first injury. It is a different and more serious situation.
Two extra signs in young children
Everything above applies. For a child too young to report symptoms, add crying that will not settle and refusing to eat or nurse.
If none of this applies
Then it is most likely a concussion, and how those are managed has changed substantially in the last few years. Strict rest in a dark room is no longer recommended. Light activity starts within the first day or two rather than at the end. Symptoms that linger past ten days have a treatment pathway rather than a waiting list. What Changed About Concussion Since You Last Heard
Resurgo assesses and treats concussion at any stage, including in people whose injury was never formally diagnosed. Clearing a head injury and rehabilitating one are two different jobs. This page is about the first.
Evidence note
Echemendia RJ, Burma JS, Bruce JM, et al. Acute evaluation of sport-related concussion and implications for the Sport Concussion Assessment Tool (SCAT6) for adults, adolescents and children: a systematic review. British Journal of Sports Medicine. 2023;57(11):722–735. Red flags as published in the Concussion Recognition Tool 6 (CRT6).
Stiell IG, Wells GA, Vandemheen KL, et al. The Canadian C-spine rule for radiography in alert and stable trauma patients. JAMA. 2001;286(15):1841–1848.
Centers for Disease Control and Prevention. Symptoms of Mild TBI and Concussion. Danger signs for adults and children.