Laboratory Testing for Lightheadedness
Order a complete blood count (CBC), basic metabolic panel (electrolytes, glucose, BUN, creatinine), and orthostatic vital signs as your initial workup for lightheadedness in most patients. 1
Core Laboratory Tests
The essential laboratory evaluation for lightheadedness should include:
- Complete blood count (CBC) to identify anemia, which is a common treatable cause of lightheadedness 1, 2
- Serum glucose (or point-of-care glucose) to detect hypoglycemia or hyperglycemia, both of which can present with lightheadedness 1
- Serum electrolytes including sodium, potassium, calcium, and magnesium to identify metabolic derangements 1
- Renal function tests (BUN and creatinine) as kidney dysfunction can contribute to electrolyte abnormalities and medication-related dizziness 1
Additional Testing Based on Clinical Context
Beyond the core tests, consider these additional studies when specific clinical features are present:
- Thyroid-stimulating hormone (TSH) if there are signs of thyroid dysfunction, as both hyperthyroidism and hypothyroidism can cause lightheadedness 3
- Troponin if cardiac ischemia is suspected based on associated chest discomfort or cardiovascular risk factors 3
- Hemoglobin A1c in patients with risk factors for diabetes or known diabetes to assess glycemic control 3
- Liver function tests if hepatic dysfunction is suspected or if the patient takes medications metabolized by the liver 3
Critical Clinical Caveat
Physical examination findings—particularly orthostatic blood pressure changes—are more diagnostically valuable than laboratory tests for most patients with lightheadedness. 1 The history can classify lightheadedness into vertigo, disequilibrium, presyncope, or nonspecific lightheadedness, which then guides the diagnostic approach 1. Laboratory testing plays a limited role compared to careful history-taking and physical examination 1.
When Laboratory Testing Has Low Yield
Avoid extensive laboratory panels in patients who:
- Have returned to baseline neurologic status 3
- Have a clear history suggesting benign paroxysmal positional vertigo or vestibular migraine 1, 4
- Have isolated lightheadedness without red flag features (no syncope, no focal neurologic deficits, no chest pain) 1
Medication Review Is Essential
Review all current medications, as polypharmacy and specific drug classes (antihypertensives, diuretics, psychotropics) are frequent culprits of presyncope-type lightheadedness. 1 This clinical assessment often provides more diagnostic value than laboratory testing 1.