Laboratory Monitoring for Lithium Therapy
Patients on lithium require baseline laboratory testing before initiation and regular ongoing monitoring every 3-6 months for renal function, thyroid function, and serum calcium, with serum lithium levels checked twice weekly during acute treatment and every 2-3 months during maintenance. 1
Baseline Laboratory Tests (Before Starting Lithium)
Before initiating lithium therapy, the following baseline tests are essential:
- Complete blood count (CBC) 2, 1
- Thyroid function tests: TSH and free T4 2, 1
- Renal function tests: Blood urea nitrogen (BUN), creatinine, and glomerular filtration rate (GFR) 2, 1
- Serum electrolytes including calcium 2, 1
- Urinalysis 2, 1
- Pregnancy test in females of reproductive age 1
These baseline assessments identify contraindications such as significant renal impairment (GFR < 60 ml/min/1.73 m²), cardiovascular disease, severe dehydration, and sodium depletion. 2
Serum Lithium Level Monitoring
Acute Phase
- Check serum lithium levels twice per week until both serum levels and clinical condition stabilize 2, 1, 3
- Blood samples must be drawn 8-12 hours after the previous dose when concentrations are relatively stable 1, 3
- Target therapeutic range during acute mania: 1.0-1.5 mEq/L 3
Maintenance Phase
- Check serum lithium levels every 2-3 months in uncomplicated cases during remission 3
- Target therapeutic range for long-term control: 0.6-1.2 mEq/L 3
- For lithium augmentation of antidepressants, lower levels (0.2-0.6 mEq/L) may be adequate 2
- Toxicity risk begins at 1.5 mEq/L and serious toxicity occurs at >2.0 mEq/L 2
Ongoing Laboratory Monitoring Schedule
Every 3-6 Months (Standard Maintenance)
- Renal function tests: BUN, creatinine, GFR 1
- Thyroid function tests: TSH (and free T4 if TSH is abnormal) 1
- Urinalysis 1
- Serum calcium (at least annually, but can be checked every 3-6 months) 1
Research data confirm that lithium is associated with increased risk of stage 3 chronic kidney disease (HR 1.93), hypothyroidism (HR 2.31), and hypercalcemia (HR 1.43), making regular monitoring critical. 4
Special Monitoring Considerations
Patients with Renal Impairment
- GFR < 60 ml/min/1.73 m²: Consider lower doses and more frequent monitoring 2
- GFR < 30 ml/min/1.73 m²: Reduce dose by 50% 2
- Creatinine clearance <50 mL/min is a significant predictor of lithium toxicity even at therapeutic doses 5
Increased Monitoring Frequency Required During:
- Intercurrent illness (temporarily suspend lithium during serious illness that increases acute kidney injury risk) 6, 1
- Planned IV radiocontrast administration 6
- Bowel preparation 6
- Prior to major surgery 6
High-Risk Populations
- Elderly patients: Use lower starting doses (150 mg/day) and monitor more frequently, as they exhibit toxicity at levels ordinarily tolerated by others 2, 3
- Women younger than 60 years: At higher risk for renal and thyroid disorders 4
- Patients with lithium concentrations higher than median: At increased risk of all adverse outcomes 4
Critical Medication Interactions Requiring Monitoring
- NSAIDs are contraindicated as they increase lithium levels and toxicity risk 6, 2, 1
- Maintain adequate hydration, especially during illness 6, 2
Early Signs of Lithium Toxicity Requiring Immediate Testing
Patients and caregivers should be educated to recognize early signs that warrant immediate lithium level and laboratory testing:
Common Pitfalls to Avoid
Despite clear guidelines, research shows that only 30% of patients meet NICE standards for lithium level monitoring, and only 50-55% meet standards for thyroid and renal function monitoring. 7 To avoid suboptimal monitoring: