Laboratory Monitoring for Patients on Lithium
Patients on lithium require regular monitoring of serum lithium levels, renal function, thyroid function, and electrolytes to prevent toxicity and ensure therapeutic efficacy.
Baseline Laboratory Tests (Before Starting Lithium)
- Complete blood count 1
- Thyroid function tests (TSH, free T4) 1
- Renal function tests (blood urea nitrogen, creatinine) 1
- Serum calcium 1
- Urinalysis 1
- Pregnancy test in females of reproductive age 1
Lithium Level Monitoring
- During initial stabilization phase: Check serum lithium levels twice weekly until stabilized 2
- Therapeutic range for maintenance: 0.6-1.2 mmol/L 2
- For acute mania: 1.0-1.5 mmol/L 2
- Blood samples should be drawn 12 hours after the last dose (trough level) 2, 3
- After stabilization, monitor lithium levels every 2-3 months 2, 3
- More frequent monitoring (every 2-4 weeks) may be needed in elderly patients, who are more sensitive to lithium toxicity 2
Ongoing Monitoring Schedule
- Renal function tests: Every 3-6 months 1
- Thyroid function tests: Every 3-6 months 1, 4
- Urinalysis: Every 3-6 months 1
- Serum calcium: Periodically (at least annually) 1
Special Monitoring Considerations
- Increase monitoring frequency during:
- Monitor more frequently in elderly patients, who often require lower doses and are more susceptible to toxicity 2
Signs of Lithium Toxicity Requiring Immediate Testing
- Early signs: tremor, nausea, diarrhea, polyuria-polydipsia 5
- More severe signs: ataxia, confusion, drowsiness, muscle weakness 2
- If these symptoms occur, lithium should be temporarily discontinued and serum levels checked immediately 2
Common Pitfalls in Lithium Monitoring
- Studies show that monitoring practices often fall short of guidelines, with only 76.2% of patients having lithium levels checked at recommended intervals 6
- 42.4% of lithium levels are below therapeutic range and 6.9% above therapeutic range in real-world settings 6
- Thyroid dysfunction typically manifests within the first 3 years of lithium treatment (91.4% of cases) 4
- Failure to standardize the timing of blood draws (12-hour post-dose) can lead to misleading results 3
Regular monitoring is essential as lithium has a narrow therapeutic index, and both subtherapeutic and supratherapeutic levels can lead to treatment failure or toxicity, respectively 7, 3.