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Lab Test: Lithium Level

    Lab Test
    • Lithium
    Description
    • Measurement of lithium levels in serum to facilitate therapeutic or toxicity monitoring
    Reference Range
    • Therapeutic range:  0.6 mEq/L - 1.2 mEq/L (0.6 mmol/L - 1.2 mmol/L)
    • Toxicity: > 1.5 mEq/L
    • Concerning Risk for Toxicity: > 2.5 mEq/L (2 mmol/L)
    Indications & Uses
    • Drug level monitoring during lithium therapy
    • Suspected lithium toxicity
    Clinical Application
    • Lithium levels above 0.8 mmol/L increase the likelihood of a therapeutic response and levels up to 1 mmol/L are usually adequate for prophylaxis and maintenance. 
      • Some patients may exhibit a therapeutic response at levels below 0.8 mmol/L.
      • Individual patient response can be quite variable. 
      • Some patients may experience poor response or toxicity despite lithium levels within the therapeutic range.  Fluctuating lithium levels may be indicative of a patient's poor compliance.  Rapid changes in lithium levels may lead to greater symptom recurrence.
    • If lithium is being used for antidepressant augmentation, a concentration of at least 0.4 mmol/L is necessary. 
    • Lithium levels should be monitored at least every 6 months after a patient has become stable with the level being a trough level 12 hours after the patient's last dose.
    • Lithium toxicity:
      • Symptoms of mild to moderate intoxication may occur at concentrations up to 2 mEq/L to 3 mEq/L, and include lethargy, drowsiness, photophobia, coarse hand tremor, muscle weakness and myoclonic twitches, nausea, vomiting, diarrhea, ataxia, nystagmus, confusion, choreoathetosis, agitation, and ECG changes.
      • Symptoms of severe intoxication may occur at concentrations above 2.5 mEq/L to 3.5 mEq/L, and include grossly impaired consciousness, increased deep tendon reflexes seizures, syncope, renal insufficiency, coma cardiovascular instability, and death. 
      • A lithium level above 1.5 mEq/L may be indicative of lithium toxicity in patients wit chronic intoxication from long-term lithium therapy.  Patients with acute intoxication have less of a correlation between lithium levels and toxic symptoms.
      • Toxicity may be predicted in some patients when lithium levels are above 1.43 mmol/L, although some patients may experience toxicity at levels within the normal therapeutic range.
      • A lithium level greater than 1.5 mEq/L may lead to subacute renal impairment.
      • Lithium levels above 4 mEq/L in chronic intoxication patients may require hemodialysis; lithium levels above 6 mEq/L likely require hemodialysis in all patients.
    • Lithium clearance is increased during pregnancy and when sodium containing fluids or supplements are being given.
    Related Tests
    • Serum creatinine
    • Serum sodium
    Drug-Lab Interactions
    • None
    Test Tube Needed
    • Red top
    • Heparin (Green top)
    Procedure
    • Obtain at least 2 mL of blood
    • Draw serum (or plasma in heparin or EDTA tube) 12 hours after last dose.
    • Separate cells from plasma/serum if test not performed in 4 hours.
    Storage and Handling
    • Store up to 24 hours at room temperature or at -20°C indefinitely
    What To Tell Patient Before & After
    • None
    References
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.

MESH Terms & Keywords

  • Lithium