Laboratory Workup for New Onset Hand Tremor
For a patient presenting with new onset hand tremor, obtain thyroid function tests (TSH, free T4), complete metabolic panel including glucose and electrolytes, complete blood count, and creatine kinase levels as the essential initial laboratory evaluation.
Essential Laboratory Tests
Metabolic and Endocrine Screening
Thyroid function tests (TSH, free T4) should be obtained as hyperthyroidism is one of the most common and treatable causes of new onset tremor, though this is based on standard clinical practice rather than tremor-specific guidelines 1.
Serum glucose should be checked immediately to exclude hypoglycemia, which can present with tremor and is a readily treatable metabolic cause 2, 1.
Serum sodium and other electrolytes should be evaluated as electrolyte disturbances, particularly hyponatremia, can manifest with neurological symptoms including tremor 2, 1.
Creatine kinase (CK) levels should be measured as inflammatory myopathies can rarely present with isolated postural and kinetic tremor as the predominant feature, and these conditions are potentially treatable 3.
Additional Basic Laboratory Tests
A complete blood count should be performed to evaluate for infection, anemia, or other hematologic abnormalities that may contribute to tremor 2.
A complete metabolic panel should be obtained to assess renal and hepatic function, as metabolic derangements can cause or exacerbate tremor 1.
Calcium and magnesium levels should be considered, particularly in patients with risk factors such as alcohol use (magnesium) or malignancy/renal failure (calcium) 1.
Targeted Testing Based on Clinical Context
Substance Use and Toxicology
- Toxicology screening should be considered in patients with suspected substance use, withdrawal (particularly alcohol or benzodiazepines), or medication effects, though routine screening has not been proven beneficial in all cases 1.
Special Populations
Pregnancy testing is required for all women of childbearing age, as this may affect diagnostic testing, treatment decisions, and medication selection 1.
Serum ferritin should be considered if symptoms suggest restless legs syndrome or other movement disorders associated with iron deficiency 4.
Important Clinical Caveats
What NOT to Do
The provided guidelines emphasize that routine extensive laboratory testing is not indicated when history and physical examination do not suggest an alternative cause. This principle from Bell's palsy guidelines applies broadly to neurological presentations 5.
Red Flags Requiring Expanded Workup
If tremor is accompanied by fever, altered mental status, or other systemic symptoms, more comprehensive evaluation including lumbar puncture may be warranted to exclude CNS infection 2.
If there are focal neurological deficits or signs of structural disease, neuroimaging (preferably MRI) should be prioritized over additional laboratory tests 1.
Clinical Context Matters
The case report of inflammatory myopathy presenting as isolated tremor highlights that CK screening is particularly important when tremor is the predominant feature without other obvious neuromuscular signs, as this represents a treatable condition that might otherwise be missed 3.
Diagnostic Approach Algorithm
- First-line labs: TSH, free T4, glucose, comprehensive metabolic panel (including sodium, calcium), CBC, CK
- Add based on history: Magnesium (alcohol use), toxicology screen (substance concerns), pregnancy test (women of childbearing age)
- Consider if initial workup negative: Ferritin (if movement disorder features), additional endocrine testing
- Avoid: Routine extensive panels without clinical indication, as this leads to false positives and unnecessary cost 5
The key principle is that laboratory testing should be guided by clinical features rather than ordered as a blanket battery, but the tests listed above represent the most clinically relevant screening for treatable causes of new onset tremor 1, 3.