Laboratory Testing for Uncomplicated Concussion
For an uncomplicated concussion with no concerning features, routine laboratory testing is not indicated and provides no diagnostic or management value. 1, 2, 3
When Laboratory Tests Are NOT Needed
- Uncomplicated concussion is a clinical diagnosis that does not require blood work, as it is a functional brain disturbance without structural injury 1, 2, 3
- The diagnosis relies on mechanism of injury, symptom assessment, cognitive evaluation, balance testing, and neurological examination—not laboratory values 1, 2
- No blood test can diagnose, confirm, or rule out a concussion 2, 3
When to Order Laboratory Tests
Laboratory testing becomes indicated only when specific red flags suggest an alternative diagnosis or complicating factor:
Immediate Laboratory Testing Required If:
- Prolonged altered mental status or seizure activity: Check serum glucose and sodium immediately, as hypoglycemia and hyponatremia can mimic or complicate concussion 4, 5
- Suspected metabolic cause: Complete metabolic panel if there are signs of systemic illness, dehydration, or electrolyte disturbance 4
- Suspected intoxication or withdrawal: Toxicology screening and alcohol level if substance use is suspected, though routine screening is not beneficial 4, 2
Additional Testing in Specific Scenarios:
- Persistent or worsening symptoms beyond expected timeframe: Consider thyroid function (TSH), vitamin B12, complete blood count, and metabolic panel to rule out other causes of cognitive symptoms 1
- Suspected infection: If fever, meningeal signs, or immunocompromised status present, obtain complete blood count and consider lumbar puncture 5
- Known medical conditions: Tailor testing to pre-existing conditions (e.g., diabetes, renal disease, electrolyte disorders) 4, 5
Critical Distinction: Concussion vs. Structural Brain Injury
The key clinical decision is distinguishing uncomplicated concussion from structural brain injury requiring neuroimaging, not ordering laboratory tests:
- CT or MRI is indicated for: prolonged loss of consciousness, focal neurological deficits, persistent altered mental status, suspected skull fracture, or deteriorating condition 1, 2
- Conventional neuroimaging is typically normal in concussion but essential when structural injury is suspected 1
- Laboratory tests do not help make this distinction 1, 2
Common Pitfalls to Avoid
- Do not order routine "concussion labs"—this practice wastes resources and does not change management for uncomplicated cases 1, 2
- Do not use laboratory testing as a substitute for proper clinical assessment including symptom checklists, cognitive evaluation, and balance testing 1, 2
- Do not delay appropriate neuroimaging in favor of laboratory testing when structural injury is suspected 1
- Remember that concussion symptoms (headache, dizziness, confusion) can overlap with metabolic disturbances—use clinical judgment to determine when labs are truly indicated 4, 3