Laboratory Testing for Dizziness
Routine laboratory testing is not indicated for isolated dizziness with normal vital signs and non-contributory examination. 1, 2
When to Order Laboratory Tests
Laboratory testing should be selective and based on specific clinical findings, not routine panels. 1
Glucose Testing
- Glucose is the most frequently abnormal test in dizziness workups and should be checked in all patients. 1, 3
- Specifically indicated if the patient has diabetes, takes hypoglycemic agents, or has prolonged fasting. 1
Cardiac-Related Testing
When cardiac etiology is suspected, obtain: 1
- Complete blood count
- Urinalysis
- Serum electrolytes
- Blood urea nitrogen and serum creatinine
- Fasting blood glucose
- Lipid profile
- Liver function tests
- Thyroid-stimulating hormone (TSH)
Red Flag Scenarios Requiring Targeted Labs
- Altered mental status, fever, or new focal neurologic deficits: Order CBC, electrolytes, renal function, and glucose. 1
- First-time seizure with dizziness: Check glucose, sodium, and pregnancy test in women of childbearing age. 1
- Vomiting, diarrhea, or dehydration: Consider electrolyte abnormalities. 2
- Affective symptoms: Consider thyroid disease testing. 2
Pregnancy Testing
- Important in women of childbearing age as it affects management decisions. 1
What NOT to Order
Low-Yield Tests to Avoid
- Routine calcium, magnesium, and phosphate testing is not supported by evidence in otherwise healthy patients. 1
- Complete blood count and serum electrolytes have low yield when ordered routinely without clinical indication. 3
- "Routine panels" without clinical justification are not cost-effective and rarely change management. 1
Critical Pitfalls to Avoid
- Over-testing based on patient anxiety rather than clinical indication leads to false positives. 1
- Ordering imaging or labs before performing bedside tests like the Dix-Hallpike maneuver wastes resources, as 43% of dizziness is due to benign peripheral vestibular disorders that can be diagnosed clinically. 3
- Clinical detection of associated neurologic symptoms is the key factor in determining diagnostic approach, not routine laboratory panels. 1
The Evidence-Based Approach
Selective testing based on clinical findings outperforms routine laboratory screening for dizziness. 1 The history and physical examination are sufficient for diagnosis in 83% of cases where a diagnosis can be made. 4 Focus on timing, triggers, and associated symptoms rather than ordering broad laboratory panels. 2, 5