There is no single definitive test for a concussion. Diagnosis relies on a combination of symptom checks, cognitive and balance assessments, and sometimes blood tests or imaging. If you or someone near you just hit their head and you’re wondering whether it’s a concussion, the most useful thing you can do right now is systematically check for specific symptoms and know which ones require an emergency room visit.
Danger Signs That Need Emergency Care
Before anything else, rule out a serious brain injury. Call 911 or go to the nearest emergency department if you notice any of the following after a bump, blow, or jolt to the head:
- Seizures or convulsions
- One pupil larger than the other, or double vision
- Repeated vomiting
- Slurred speech, weakness, numbness, or loss of coordination
- Inability to wake up, stay awake, or increasing drowsiness
- Inability to recognize people or places
- A headache that keeps getting worse and won’t go away
- Unusual behavior, increasing confusion, restlessness, or agitation
For infants and toddlers, add two more warning signs: crying that won’t stop no matter what you do, and refusing to nurse or eat. Young children can’t tell you their head hurts or that they’re seeing double, so behavioral changes are your primary signal.
Symptoms You Can Check Right Now
Most concussions don’t involve a loss of consciousness. The symptoms are subtler, and some won’t appear for hours or even days after the injury. That delayed onset is one reason concussions get missed. Here’s what to watch for, broken into categories:
Physical: headache, nausea, dizziness, blurry vision, sensitivity to light or noise, balance problems, feeling sluggish or “foggy.”
Cognitive: difficulty concentrating, trouble remembering new information, feeling mentally slow, confusion about recent events, repeating the same questions.
Emotional: irritability, sadness, nervousness, or mood swings that seem out of proportion to the situation.
Sleep-related: sleeping much more or less than usual, or difficulty falling asleep.
Symptoms are often most severe right after the injury, but don’t assume you’re in the clear just because you feel fine an hour later. Keep monitoring for at least 24 to 48 hours. If you’re watching someone else, especially a child, trust your instinct about what’s normal for them. Changes in how they act or feel are worth reporting to a healthcare provider even if they seem minor.
Simple Cognitive Checks You Can Do at Home
Professional concussion assessments test orientation, memory, and concentration. You can approximate some of these informally. Ask the person (or ask yourself, though self-assessment after a head injury is unreliable):
- What month, day of the week, and year is it?
- What time is it right now (within an hour)?
- Can you recite the months of the year backward, starting from December?
- Can you repeat a short string of numbers in reverse order (for example, 7-4-2 becomes 2-4-7)?
Struggling with any of these, especially when the person could normally handle them easily, is a red flag. These questions come directly from the Sport Concussion Assessment Tool (SCAT6), the standardized test used on sidelines and in clinics worldwide. The full SCAT6 also includes a 22-item symptom checklist rated by severity, a 10-word memory recall test, and timed balance tasks, but those require a trained provider to administer and score properly.
Balance and Eye Movement Tests
Concussions frequently disrupt the systems that coordinate balance, vision, and movement. Two assessments specifically target this.
The balance portion of the SCAT6 uses the modified Balance Error Scoring System. The person stands in three positions on a firm surface: feet together, one foot in front of the other (tandem stance), and on one leg. Each stance is held for 20 seconds with eyes closed. Wobbling, stepping out of position, or needing to open the eyes to stay upright all count as errors. A timed heel-to-toe walk, sometimes performed while counting backward by sevens, adds a dual-task challenge that makes hidden deficits more obvious.
The Vestibular Ocular Motor Screening (VOMS) tests five areas: smooth eye tracking (following a slow-moving target), rapid eye movements (looking quickly between two points), near point of convergence (how close an object can get to your nose before you see double), the vestibulo-ocular reflex (keeping focus while moving your head), and visual motion sensitivity (how you react to busy visual scenes). VOMS requires only a tape measure and a metronome, yet research shows it is about 90% accurate in identifying concussions. If any of these tasks provoke a headache, dizziness, nausea, or fogginess, that strongly suggests a concussion. A healthcare provider needs to run the full screen, but you can get a rough sense at home by slowly tracking a finger side to side and up and down. If that simple motion triggers symptoms, it’s worth getting evaluated.
Computerized Neurocognitive Testing
ImPACT is the most widely used computerized concussion test. It measures reaction time, attention, working memory, processing speed, and visual recall through a series of timed computer tasks. The real value of ImPACT is comparison: many athletes and students take a baseline test before the season starts, so after a head injury, a provider can compare post-injury scores to the individual’s own normal performance. Without a baseline, the test is less informative because there’s no personal reference point, but it can still flag significant deficits. ImPACT is administered in a clinical setting, not something you’d do on your own at home.
Blood Tests for Concussion
An FDA-cleared blood test can now help evaluate head injuries. It measures two proteins that leak from damaged brain cells into the bloodstream after an injury. Elevated levels of these proteins suggest the brain has been affected and can help a clinician decide whether imaging is necessary. The test is usable up to 24 hours after injury. It’s currently available in emergency departments and some urgent care settings, not as a home test, but it represents a meaningful shift toward objective concussion diagnosis rather than relying solely on symptom reports.
Why a CT Scan Might Not Show Anything
If you go to the ER after a head injury, you’ll likely get a CT scan. It’s important to know what a CT scan can and cannot do. CT is excellent at detecting skull fractures and bleeding in the brain, which are the life-threatening concerns. But a concussion is a functional injury, meaning it disrupts how the brain works without necessarily causing visible structural damage. CT scans miss a large proportion of concussions entirely. MRI is significantly more sensitive, detecting abnormalities in about 90% of acute brain injuries compared to roughly 60% for CT. However, MRI is slower and more expensive, so it’s not the first-line tool in an emergency. A normal CT scan does not mean you don’t have a concussion. It means you likely don’t have a brain bleed.
Monitoring at Home After a Head Injury
If a healthcare provider clears someone to recover at home, or if you’re watching someone before they can get to a provider, here’s what monitoring looks like. Check on the person regularly, especially in the first 24 hours. Watch for new symptoms or existing symptoms getting worse. There’s a persistent myth that you need to wake someone every two hours through the night, but current CDC guidance says to let the person sleep normally and maintain their regular bedtime routine. Preventing sleep can actually slow recovery. The key is that the person can be woken up if you try. If they can’t be roused, that’s an emergency.
For children, monitor them for changes in behavior, mood, and energy level. You know your child’s baseline better than any screening tool. If something feels off, trust that instinct and contact their provider. Symptoms can evolve over several days, so don’t limit your vigilance to the first night.
Early Activity and Recovery
The latest international consensus on concussion in sport, published in 2023, shifted away from the old advice of lying in a dark room until all symptoms resolve. Strong evidence now supports light aerobic exercise as an early intervention. This means gentle walking or stationary cycling below the threshold that worsens symptoms, typically starting within the first few days. Cervicovestibular rehabilitation, which targets neck pain, headaches, dizziness, and balance problems through guided exercises, is also recommended when those symptoms are present. If symptoms persist beyond four weeks, a multimodal clinical assessment using standardized tools is the recommended next step rather than continued wait-and-see.