What laboratory tests are required for patients starting lithium therapy?

Laboratory Tests Required for Lithium Therapy

Before initiating lithium therapy, patients should undergo baseline laboratory tests including complete blood count, thyroid function tests, urinalysis, blood urea nitrogen, creatinine, and serum calcium levels. 1, 2

Initial Laboratory Assessment

• Complete blood count (CBC) - Lithium can cause an increase in white blood cell count 3
• Thyroid function tests (TSH) - Lithium is associated with increased risk of hypothyroidism 1, 4
• Renal function tests:
  • Blood urea nitrogen (BUN)
  • Serum creatinine
  • Urinalysis 1, 2
• Serum calcium - Lithium can cause hypercalcemia 4
• Pregnancy test for women of childbearing age 1

Lithium Level Monitoring

• Initial phase: Serum lithium levels should be checked twice per week during the acute phase until serum concentrations and clinical condition have stabilized 5, 2
• Blood samples for lithium levels should be drawn 8-12 hours after the previous dose (trough level) when concentrations are relatively stable 2
• Target therapeutic range: 0.6-1.2 mEq/L for maintenance therapy 2, 6

Ongoing Monitoring Schedule

• Lithium levels: Every 3-6 months once stable 1
• Renal function: Every 3-6 months 1, 4
• Thyroid function: Every 3-6 months 1, 4
• Calcium levels: Should be monitored regularly 4

Special Considerations

• Women are at greater risk of developing renal and thyroid disorders from lithium therapy 4
• Patients with higher than median lithium concentrations are at increased risk of adverse outcomes 4
• More frequent monitoring is needed for:
  • Patients taking medications that interact with lithium (NSAIDs, diuretics) 5
  • Patients showing signs of toxicity 5, 2
  • Elderly patients 2
  • Patients with pre-existing renal or thyroid disease 1

Common Pitfalls to Avoid

• Failing to establish baseline renal function before initiating lithium therapy 5
• Inconsistent monitoring - Studies show that as many as 21% of patients start lithium without baseline creatinine assessment, and monitoring compliance decreases over time 7
• Overlooking the need for more frequent monitoring if symptoms of toxicity appear 5
• Relying solely on serum levels without clinical assessment - accurate patient evaluation requires both clinical and laboratory analysis 2

Lithium has a narrow therapeutic window, making laboratory monitoring essential for safe and effective treatment. The monitoring schedule should be strictly followed to prevent serious complications including renal dysfunction, hypothyroidism, and hypercalcemia 2, 4.