There is no single test that confirms a concussion. Instead, concussions are identified through a combination of symptom checks, cognitive and balance assessments, and sometimes blood tests or brain scans. Whether you’re checking someone at home after a fall or understanding what a doctor will do in the clinic, knowing what each layer of testing looks for helps you act quickly and confidently.
What to Watch for Right Away
A concussion can show symptoms immediately or develop them over minutes to hours. The first thing to assess is whether the situation is an emergency. Some signs after a blow to the head point to a more serious brain injury that needs immediate medical attention. Call 911 or go to the emergency room if you see any of the following:
- Seizures or convulsions
- One pupil noticeably larger than the other
- Repeated vomiting (two or more episodes)
- Slurred speech, weakness, numbness, or loss of coordination
- Inability to recognize familiar people or places
- A headache that keeps getting worse
- Increasing confusion, restlessness, or agitation
- Loss of consciousness, extreme drowsiness, or inability to stay awake
For infants and toddlers, all the same red flags apply, plus inconsolable crying or refusal to nurse or eat. If none of these danger signs are present, a concussion is still possible, and the person should be monitored closely and seen by a healthcare provider.
How to Check Someone at Home
Most concussions don’t involve a trip to the ER. If the injury seems mild, you can start by running through a basic set of observations. Ask the person simple questions: What day is it? Where are you? What happened? Difficulty answering these correctly, or giving confused or delayed responses, is a red flag. Watch for visible signs like a blank stare, slowed reactions, or seeming “off.”
Over the first 24 to 48 hours, monitor them regularly and watch for any changes in how they act or feel. Contrary to an old belief, you do not need to wake someone up repeatedly during the night. The CDC’s current guidance is to let the person sleep as usual. What matters more is checking on them when they are awake and noting if symptoms worsen, new symptoms appear, or their behavior changes. Share any observations with their healthcare provider.
Common concussion symptoms to track include headache, pressure in the head, dizziness, blurred vision, sensitivity to light or noise, feeling foggy or slowed down, difficulty concentrating or remembering, nausea, fatigue, irritability, and trouble falling asleep. You don’t need to see all of these. Even a few, appearing after a head impact, suggest a concussion.
Symptom Checklists Used by Professionals
When a healthcare provider evaluates a possible concussion, they typically use a structured symptom checklist. The most widely used tool in sports is the SCAT6 (Sport Concussion Assessment Tool, 6th edition), which asks the person to rate 22 specific symptoms on a scale from 0 to 6. These range from headache, neck pain, and nausea to emotional symptoms like sadness, nervousness, and irritability. The total severity score can reach as high as 132, giving clinicians a precise snapshot of how the person feels at that moment.
A separate version, the Child SCAT6, is designed for younger athletes. It uses modified symptom checklists and adjusted cognitive tasks appropriate for children, since kids often describe and experience concussion symptoms differently than adults.
Cognitive and Memory Testing
Concussions frequently affect thinking speed, memory, and concentration, sometimes before more obvious symptoms like headache kick in. Professional assessments test these functions directly.
On the sideline or in a clinic, providers use a standardized cognitive screen that includes orientation questions (month, date, day of the week, year, time of day), immediate memory recall of a 10-word list over three trials, concentration tasks like reciting digits backward or months in reverse order, and delayed recall of those same words at least five minutes later. These are scored out of 50 total points. Even small drops in performance compared to a healthy baseline can signal a concussion.
In sports settings, clinicians also ask Maddocks questions, which test memory for recent events in the game: What venue are we at? Which half is it? Who scored last? What team did you play last week? Did your team win? These are useful because they tap into the kind of short-term, context-specific memory that concussions disrupt most reliably. A score below 5 out of 5 is concerning.
Computerized Neurocognitive Tests
Tools like ImPACT are computerized tests that measure verbal and visual memory, brain processing speed, and reaction time. Ideally, athletes take a baseline test before their season starts while healthy. If a concussion happens, they’re tested again, and the two sets of scores are compared. A noticeable decline in any domain helps confirm the injury and guides decisions about treatment and when it’s safe to return to activity. These tests take about 20 to 30 minutes and are commonly used in high school, college, and professional sports programs.
Balance and Coordination Tests
Because concussions affect the brain’s ability to maintain balance, physical testing is a core part of any evaluation. The Balance Error Scoring System (BESS) is one of the most common tools. It involves three stances: standing with both feet together, standing on one leg (the non-dominant leg), and standing heel-to-toe in a tandem position. Each stance is held for 20 seconds with eyes closed, first on a firm surface and then on a foam pad.
An observer counts errors: opening the eyes, lifting hands off the hips, stepping or stumbling, lifting the forefoot or heel, moving the hip more than 30 degrees, or failing to return to position within 5 seconds. More errors than expected, particularly compared to a baseline score, suggest the brain is struggling with the automatic processes that keep you steady.
The SCAT6 also includes timed tandem gait, where the person walks heel-to-toe along a line as quickly as possible, and a dual-task version where they walk while counting backward by sevens. Adding a mental task to a physical one makes concussion-related deficits more obvious, since a healthy brain handles both easily but an injured one often can’t.
Eye Movement Screening
One of the more sensitive ways to detect a concussion involves testing how the eyes move and respond. The Vestibular/Ocular Motor Screening (VOMS) protocol checks several distinct functions and notes whether each one provokes symptoms like headache, dizziness, nausea, or fogginess.
Smooth pursuits test whether the eyes can follow a slowly moving target. Saccades test rapid eye movements, asking the person to snap their gaze back and forth between two points. Near point convergence checks whether both eyes can track a target as it moves toward the nose. In a healthy person, the eyes converge smoothly; after a concussion, one eye often drifts outward too early. The vestibular-ocular reflex test has the person focus on a fixed target while turning their head quickly side to side or up and down. Finally, a visual motion sensitivity test involves rotating the head and trunk together while focusing on a thumb held at arm’s length.
Each of these tasks stresses a different pathway connecting the eyes, inner ear, and brain. Symptoms triggered during any of them point to specific types of concussion-related dysfunction and help clinicians tailor rehabilitation.
Blood Tests for Concussion
A relatively new option is an FDA-cleared blood test that can help evaluate a suspected concussion within 24 hours of injury. The i-STAT TBI test measures two proteins that leak from damaged brain cells into the bloodstream after an injury. Elevated levels of these proteins indicate a possible brain injury and help doctors decide whether a CT scan is needed. The test is primarily used in emergency departments and is most useful for ruling out the need for a scan rather than diagnosing a concussion on its own.
When Brain Scans Are Used
A standard CT scan does not detect a concussion. What it does detect is bleeding, swelling, or skull fractures, which are the dangerous complications a doctor wants to rule out. Not everyone with a suspected concussion needs a scan. Doctors use clinical decision rules to determine who does.
The most widely used criteria flag patients as high-risk for a serious finding if they haven’t returned to full alertness within two hours, show signs of a skull fracture, have vomited two or more times, or are 65 or older. Medium-risk factors include memory loss for more than 30 minutes before the injury or a dangerous mechanism of injury (like being hit by a car or falling from a significant height). Using these criteria, only about a third to half of head injury patients actually need a CT scan.
MRI scans are more detailed than CT but are not routine for acute concussions. They may be ordered later if symptoms persist for weeks and the clinical team wants a closer look at brain structure. Specialized MRI techniques can sometimes reveal subtle damage that standard imaging misses, but these are typically reserved for research settings or complex cases.
How All the Pieces Fit Together
No single test is definitive. A concussion diagnosis comes from layering multiple assessments: reported symptoms, cognitive performance, balance, eye function, and sometimes blood work or imaging. The 2022 international consensus on sport-related concussion defines the injury as a traumatic brain injury from a direct or transmitted force to the brain that triggers a cascade of changes at the cellular level. Symptoms and signs may appear immediately or evolve over hours, and they commonly resolve within days, though some cases take longer.
The most important factor in accurate testing is comparison. Knowing how someone performs on cognitive and balance tests when healthy makes it far easier to detect subtle changes after a head impact. If you or your child plays a contact sport, completing a preseason baseline assessment through a program like ImPACT or a clinical SCAT6 evaluation gives providers a personal reference point that generic averages can’t match. Without a baseline, clinicians rely on population norms, symptom reports, and clinical judgment, which still work but leave more room for borderline cases to slip through.