Baseline Laboratory Testing for Lithium Therapy
Before initiating lithium therapy, obtain complete blood count (CBC), thyroid function tests (TSH, free T4), renal function tests (BUN, creatinine, urinalysis), serum calcium, and pregnancy test for women of childbearing age. 1
Essential Baseline Tests
Renal Function Assessment
- Blood urea nitrogen (BUN) and creatinine are mandatory before starting lithium, as the drug is almost exclusively excreted by the kidneys and renal insufficiency is considered a contraindication to lithium use 1, 2
- Urinalysis should be performed to establish baseline kidney function 1
- Failing to establish baseline renal function before initiating lithium can lead to serious complications, as lithium clearance decreases with aging and renal impairment 1, 3
Thyroid Function Testing
- Thyroid-stimulating hormone (TSH) and free thyroid hormones (T4 and T3) must be checked at baseline, as lithium is strongly associated with hypothyroidism and goiter 1, 4
- Lithium decreases thyroid hormone synthesis and release at the cellular level and increases propensity to thyroid autoimmunity 4
- Thyroid autoantibodies (anti-thyroid peroxidase and TSH receptor antibodies) should be considered, particularly in middle-aged females (≥50 years) and those with family history of thyroid disease 4
Hematologic Testing
- Complete blood count with differential is recommended at baseline 1
- Lithium treatment is associated with significant increases in white blood cell counts 5
Metabolic Parameters
- Serum calcium levels should be measured before starting therapy, as lithium is associated with hypercalcemia and parathyroid dysfunction 1, 3
- Women are at greater risk of developing renal and thyroid disorders than men, with younger women at higher risk than older women 3
Reproductive Considerations
- Pregnancy testing is mandatory for women of childbearing age before initiating lithium therapy 1
- Lithium clearance increases by 30-50% during the last months of pregnancy due to increased glomerular filtration rate 2
Critical Monitoring Framework
The FDA emphasizes that lithium toxicity is closely related to serum lithium levels and can occur at doses close to therapeutic levels, making facilities for prompt and accurate serum lithium determinations essential before initiating therapy 6. Higher than median lithium concentrations are associated with increased risk of all adverse outcomes including renal dysfunction, hypothyroidism, and hypercalcemia 3.