Should I check the lithium level in a patient with a history of lithium use for bipolar disorder who has stopped taking the medication and is now hospitalized?

Should You Check Lithium Level Before Restarting?

Yes, you should check the lithium level before restarting lithium in this patient, even though she reports stopping the medication. This is critical for safety assessment and to guide your initial dosing strategy.

Why Checking the Level is Essential

The primary reason to check the lithium level is to verify that the patient actually stopped taking lithium and to rule out occult toxicity. Patients may misreport medication adherence, and lithium can accumulate dangerously even at "therapeutic" doses in certain clinical contexts 1, 2.

Key Safety Considerations

• Lithium toxicity can occur with normal serum levels in patients with renal impairment, making clinical assessment alone insufficient 1.
• Patients with chronic kidney disease (even stage 3) are at significantly higher risk for toxicity, with creatinine clearance <50 mL/min being a significant predictor of non-overdose-related lithium toxicity 2.
• Lithium has a narrow therapeutic index (0.6-1.5 mEq/L therapeutically), and toxicity risk is very high in patients with renal disease, dehydration, or sodium depletion 3.

Clinical Algorithm for This Scenario

Step 1: Immediate Assessment (Before Any Lithium Dosing)

• Draw serum lithium level immediately upon hospital admission 3.
• Obtain comprehensive metabolic panel including creatinine, BUN, and electrolytes 4.
• Calculate creatinine clearance to assess renal function 2.
• Check thyroid function (TSH, free T4) and complete blood count 4.

Step 2: Interpret Results and Plan

• If lithium level is detectable (>0.1 mEq/L): The patient has not fully stopped lithium, or stopped very recently. Wait for complete clearance before restarting, and investigate why levels persist 1.
• If lithium level is undetectable AND renal function is normal: Safe to restart lithium using standard acute mania dosing (600 mg TID targeting 1.0-1.5 mEq/L) 3.
• If lithium level is undetectable BUT creatinine clearance <50 mL/min: Lithium may still be appropriate but requires extreme caution with reduced dosing and more frequent monitoring 3, 2.

Step 3: Monitoring During Restart

• Check serum lithium levels twice weekly during the acute phase until stable 3.
• Draw levels 8-12 hours after the previous dose for accurate interpretation 3.
• Monitor for early signs of toxicity (tremor, nausea, diarrhea, polyuria) regardless of serum level 5.

Critical Pitfalls to Avoid

• Never assume the patient stopped lithium based on self-report alone - medication adherence is notoriously unreliable, and >90% of noncompliant adolescents relapse 6.
• Do not restart lithium without baseline renal function assessment - renal impairment dramatically increases toxicity risk even at standard doses 2.
• Avoid treating "the numbers" alone - clinical signs of toxicity can occur with normal serum levels, particularly in patients with chronic kidney disease 1.
• Never restart lithium in patients with significant renal disease (GFR <30 mL/min) without extreme caution and daily monitoring - the FDA contraindication is clear that risk is "very high" in such patients 3.

Special Considerations for Hospitalized Patients

• Abrupt lithium discontinuation increases relapse risk dramatically, with withdrawal associated with increased relapse especially within 6 months 6.
• If the patient truly stopped lithium and is now hospitalized with mania, this represents a preventable relapse that underscores the importance of maintenance therapy 6.
• Consider why the patient stopped lithium - side effects, poor adherence, or lack of understanding about maintenance therapy - and address these barriers before discharge 7.

Alternative Approach if Lithium is Contraindicated

If the baseline assessment reveals contraindications to lithium (severe renal impairment, cardiovascular disease, severe dehydration), consider alternative first-line agents for acute mania 3:

• Valproate (particularly effective for mixed episodes) 6.
• Atypical antipsychotics (aripiprazole, olanzapine, risperidone, quetiapine) 6.
• Combination therapy with mood stabilizer plus antipsychotic for severe presentations 6.