Laboratory Testing for Dizziness
In patients presenting with dizziness who have returned to baseline neurologic status with normal vital signs and a non-contributory history and physical examination, routine laboratory testing is generally not indicated, as the yield is extremely low and abnormalities are typically predicted by clinical findings. 1, 2
Clinical Context and Approach
The decision to order laboratory tests for dizziness should be guided entirely by findings from the history and physical examination, not performed routinely. 1, 2 The key is identifying red flags that suggest serious underlying pathology requiring immediate workup versus benign peripheral causes.
When Laboratory Testing IS Indicated
Order targeted laboratory studies when specific clinical features are present:
Altered mental status, fever, or new focal neurologic deficits - These patients require extensive evaluation including complete blood count, electrolytes, renal function, and glucose 3
Orthostatic vital sign changes - Check complete blood count (for anemia), electrolytes, and glucose 2
Suspected cardiac etiology - If heart failure or cardiac disease is suspected, obtain: complete blood count, urinalysis, serum electrolytes (including calcium and magnesium), blood urea nitrogen, serum creatinine, fasting blood glucose, lipid profile, liver function tests, and thyroid-stimulating hormone 3
First-time seizure with dizziness - Check glucose (most common abnormality), sodium, and consider pregnancy test in women of childbearing age 3
When Laboratory Testing is NOT Routinely Needed
For otherwise healthy patients with isolated dizziness who have returned to baseline, extensive laboratory screening has very low diagnostic yield (approximately 2-4% positivity rate). 3, 1 Studies consistently show that when abnormalities are found, they are usually:
- Predicted by history and physical examination 3
- Clinically insignificant 3
- False positives (8 times more common than true positives) 3
Specific Laboratory Considerations
Glucose
- Most frequently abnormal test in dizziness workups 3
- However, hypoglycemia is rare in patients without diabetes or other risk factors 3
- Consider checking if patient has diabetes, takes hypoglycemic agents, or has prolonged fasting 3
Electrolytes
- Hyponatremia is occasionally found but usually suspected clinically (psychogenic water ingestion, diuretic use) 3
- Routine calcium, magnesium, and phosphate testing not supported by evidence in otherwise healthy patients 3
Thyroid Function
- Consider TSH if cardiac symptoms present or in patients with heart failure 3
- Not routinely indicated for isolated dizziness 1
Pregnancy Testing
- Important in women of childbearing age as it affects management decisions 3
Common Pitfalls to Avoid
Over-testing based on patient anxiety rather than clinical indication - This leads to false positives requiring additional unnecessary workup 3
Ordering "routine panels" without clinical justification - Multiple studies demonstrate this approach is not cost-effective and rarely changes management 3, 1
Failing to check orthostatic vital signs before ordering labs - This simple bedside test often provides more diagnostic information than laboratory studies 2
Not considering medication effects - Many medications cause dizziness/presyncope; medication review is more valuable than laboratory testing in many cases 2
Evidence Quality Note
The evidence consistently shows across multiple studies that selective testing based on clinical findings outperforms routine laboratory screening for dizziness. 3, 1, 2 The ACR Appropriateness Criteria emphasizes that clinical detection of associated neurologic symptoms is the key factor in determining diagnostic approach, not routine laboratory panels. 3