How many days after starting lithium (lithium carbonate) should lithium levels be drawn?

Timing of Lithium Level Monitoring After Initiation

Lithium levels should be drawn twice per week during the acute phase after starting therapy until levels and clinical condition stabilize. 1

Initial Monitoring Protocol

Frequency During Acute Phase

• Check serum lithium concentrations twice weekly after initiation until both therapeutic levels and clinical stability are achieved 1
• This intensive monitoring is critical because lithium toxicity can occur at doses close to therapeutic levels, with toxicity beginning at 1.5 mEq/L and serious toxicity at >2.0 mEq/L 2, 1

Timing of Blood Draw

• Draw blood 12 hours after the last dose for standard-release formulations 3, 4, 5
• Draw blood 24 hours after the last dose if using once-daily sustained-release preparations 5
  • The 12-hour level with once-daily dosing will be artificially elevated (approximately 1.3 times higher than true trough) and may lead to underdosing 5
  • However, some evidence suggests that 12-hour levels remain appropriate even for extended-release formulations because absorption is essentially complete by 8 hours and levels converge with immediate-release at 12 hours 6

Target Therapeutic Range

Standard Maintenance Levels

• Maintain serum concentrations between 0.6-0.8 mEq/L for most patients 3
• For sustained-release preparations, aim for the upper range (0.8-1.0 mEq/L) rather than 0.6-0.8 mEq/L 3
• Lower levels (0.2-0.6 mEq/L) may be adequate when lithium is used to augment antidepressants 1

Special Population Considerations

Renal Impairment

• Patients with GFR < 60 ml/min/1.73 m² require lower doses and more frequent monitoring 1
• Reduce dose by 50% if GFR < 30 ml/min/1.73 m² 1
• Renal insufficiency is considered a relative contraindication, especially with sodium restriction 3

Elderly Patients

• Start with lower doses (150 mg/day) due to increased sensitivity and reduced clearance 1
• Typical maintenance doses are 15-20 mmol (550-740 mg) daily for patients >60 years 3

Critical Safety Monitoring

Baseline Laboratory Tests Required

• Complete blood count 1
• Thyroid function (TSH, free T4) 1
• Renal function (BUN, creatinine, GFR) 1
• Serum electrolytes including calcium 1
• Urinalysis 1

Common Pitfalls to Avoid

• Never use NSAIDs concurrently as they increase lithium levels and toxicity risk 1
• Ensure adequate hydration, especially during intercurrent illness 1
• Avoid sodium depletion or severe dehydration 1
• Standardize blood sampling time, dosage schedule, and tablet brand for accurate monitoring 4

Pregnancy Considerations

• Lithium clearance increases 30-50% during the last months of pregnancy due to increased GFR 3
• Associated with increased cardiovascular anomalies in newborns, particularly tricuspid valve abnormalities 7
• Requires monitoring every 3 days during pregnancy 7