When should the first bloodwork to check lithium levels be done after starting lithium carbonate?

Timing of First Lithium Level After Starting Lithium Carbonate

The first bloodwork to check lithium levels should be done twice per week during the acute phase, until the serum level and clinical condition of the patient have stabilized. 1

Initial Monitoring Protocol

• Blood samples should be drawn 12 hours after the last dose when lithium concentrations are relatively stable 1, 2
• For standard formulations, this typically means drawing blood in the morning before the first dose of the day
• For once-daily extended-release formulations, the 12-hour mark is still recommended as the ideal time for drawing blood levels 2

Monitoring Schedule Based on Treatment Phase

Acute Phase

• Obtain serum lithium levels twice weekly until stabilized 1, 3
• Target serum concentration during acute phase: 1.0-1.5 mEq/L for standard formulations 1

Maintenance Phase

• Once stabilized, monitor every 2-3 months 3
• Target maintenance serum concentration: 0.6-0.8 mEq/L for standard formulations; 0.8-1.0 mEq/L for sustained-release formulations 3, 4

Interpretation of Lithium Levels

• Therapeutic range: 0.6-1.2 mEq/L 1
• Levels >1.5 mEq/L may have mild and reversible toxic effects 3
• Levels >2.0 mEq/L may cause neurological symptoms 3
• Low lithium levels are associated with higher relapse rates 3

Special Considerations

• Elderly patients often require reduced dosage and may exhibit toxicity at serum levels normally tolerated by others 1
• Patients with renal impairment require more frequent monitoring due to reduced lithium clearance 3, 4
• During pregnancy, lithium clearance increases by 30-50% in the last months, necessitating dose adjustments 4

Common Pitfalls to Avoid

1. Incorrect timing of blood draws: Samples taken too soon after a dose may show falsely elevated levels
2. Relying solely on serum levels: Accurate patient evaluation requires both clinical and laboratory analysis 1
3. Inadequate monitoring frequency: Failure to monitor twice weekly during initial stabilization increases risk of toxicity
4. Not adjusting for formulation type: Extended-release formulations may require different target ranges 4

Remember that lithium has a narrow therapeutic index, making regular monitoring essential for both efficacy and safety. The monitoring schedule should be strictly followed to prevent potential toxicity while ensuring therapeutic benefit.