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Paediatric Laboratory Medicine

Lithium (B)

Clinical Significance

Lithium carbonate is indicated in the treatment of manic episodes of manic-depressive illness. Maintenance therapy prevents or diminishes the intensity of subsequent episodes in those manic-depressive patients with a history of mania. Typical symptoms of mania include pressure of speech, motor hyperactivity, reduced need for sleep, flight of ideas, grandiosity, elation, p.o. judgment, aggressiveness, and possibly hostility. When given to a patient experiencing a manic episode, lithium carbonate may produce a normalization of symptomatology within 1 to 3 weeks. 

Preclinical studies have shown that lithium alters sodium transport in nerve and muscle cells and effects a shift toward intraneuronal metabolism of catecholamines, but the specific biochemical mechanism of lithium action in mania is unknown.

 Adverse reactions may be encountered at serum lithium levels below 1.5 mmol/L. Mild to moderate adverse reactions may occur at levels from 1.5 to 2.5 mmol/L., and moderate to severe reactions may be seen at levels of 2.0 mmol/L and above.

Fine hand tremor, polyuria, and mild thirst may occur during initial therapy for the acute manic phase, and may persist throughout treatment. 

Diarrhea, vomiting, drowsiness, muscular weakness, and lack of coordination may be early signs of lithium intoxication, and can occur at lithium levels below 2.0 mmol/L. At higher levels, ataxia, giddiness, tinnitus, blurred vision, and a large output of dilute urine may be seen. Serum lithium levels above 3.0 mmol/L may produce a complex clinical picture, involving multiple organs and organ systems.

Test Name

Lithium (B)

Test Code


Drug Class

Psychotropic Drugs




Abbott Architect ci4100

External Proficiency Testing


Turn Around Time

Daily, Stat

Specimen Type


Minimum Specimen Requirements

0.2 mL


Trough sample: 0 – 30 minutes before next dose

Approval is not required

CPT Codes


Shipping and Contact Information

The Hospital for Sick Children
Rapid Response Laboratory
170 Elizabeth Street, Room 3642
Toronto, ON
M5G 2G3
Phone: 416-813-7200
Phone: 1-855-381-3212

Therapeutic Range

0.5 – 1.3 mmol/L

Critical Values

> 1.5 mmol/L