Lab Test: Lithium Level
- 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)
- 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.
- 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.
MESH Terms & Keywords