Laboratory Tests for Nausea Evaluation
For patients presenting with nausea, a basic laboratory workup should include complete blood count, comprehensive metabolic panel, urinalysis, and pregnancy test in women of childbearing age. 1
Initial Laboratory Assessment
- Complete blood count (CBC): To assess for infection, anemia, or other hematologic abnormalities that may contribute to nausea 1
- Comprehensive metabolic panel: To evaluate electrolytes, renal function, and liver function tests 1
- Serum electrolytes (sodium, potassium): To assess for electrolyte imbalances that may cause or result from vomiting 1
- Blood glucose: To rule out diabetic complications or hypoglycemia 1
- Renal function (BUN, creatinine): To assess for pre-renal acute renal failure due to dehydration 1
- Liver function tests (AST, ALT, bilirubin): To evaluate for hepatic causes of nausea 1
- Urinalysis: To assess hydration status and rule out urinary tract infection 1
- Urine pregnancy test: Essential in women of childbearing age to rule out pregnancy-related nausea 1
Additional Testing Based on Clinical Presentation
For Suspected Gastrointestinal Causes:
- Amylase and lipase levels: To evaluate for pancreatitis 2
- Stool studies with cultures: If infectious gastroenteritis is suspected 2
For Suspected Metabolic/Endocrine Causes:
- Thyroid-stimulating hormone (TSH): To rule out thyroid dysfunction 2
- Testing for Addison's disease: If adrenal insufficiency is suspected 1
For Suspected Cyclic Vomiting Syndrome:
- Basic workup: CBC, electrolytes, glucose, liver function tests, and lipase 1
- Urinalysis: To rule out urinary tract infection and assess for ketones 1
Imaging Studies to Consider
- Abdominal radiography: For suspected bowel obstruction 1
- Abdominal ultrasonography: To evaluate gallbladder, liver, and pancreas 2
- Abdominal CT scan: For suspected intra-abdominal pathology 2
- Head CT: If intracranial process is suspected (especially with headache, altered mental status) 2
Special Considerations
- For persistent nausea with vomiting: Evaluate for acid-base disorders with arterial blood gas if clinically indicated 1
- For suspected gastroparesis: Consider gastric emptying study, though this should not be ordered routinely in all cases 1
- For suspected cannabis hyperemesis syndrome: Document cannabis use patterns and duration 1
- For suspected bowel obstruction: Serum bicarbonate levels, arterial blood pH, lactic acid level, and marked leukocytosis may help diagnose intestinal ischemia 1
Important Caveats
- Laboratory testing should be guided by the patient's presentation, severity of symptoms, and suspected etiology 3
- Repeated endoscopic or imaging studies should be avoided unless there is a change in clinical status 1
- In patients with mild, acute nausea of obvious etiology (e.g., viral gastroenteritis), extensive laboratory testing may not be necessary 3
- Gastric emptying studies should not be performed during an acute episode of vomiting as results will be uninterpretable 1
Remember that the laboratory evaluation should be tailored to the clinical presentation, with more extensive testing reserved for patients with severe, persistent, or concerning symptoms 2, 3.