Adult patient:
Clotted blood tube
(Serum gel separator clot activator tube)
Minimum blood volume: 5 mL
Paediatric patient:
Paediatric clotted blood tube
Number of vials: 1
Minimum blood volume: 0.8 mL
Authorisation code required
No
24 Hr available service
No
For suspected lithium overdose cases, please call Duty Biochemist for 'Urgent' lithium level testing.
Precaution
For monitoring of lithium therapy, blood should be drawn 8 - 12 hours after the last dose.
Method
Spectrophotometry
Reference interval
| Therapeutic: | 0.6 - 1.2 mmol/L |
| Toxicity reported: | > 2.0 mmol/L |
(Source: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics 4th ed. 2005)
Clinical indication
Therapeutic drug monitoring
Result interpretation
Lithium half-life is 8 - 20 hours; may be prolonged in renal failure.
When levels are > 1.5 mmol/L, lithium therapy should be discontinued and the patient assessed for toxic symptoms. Symptoms of lithium intoxication include: sluggishness, drowsiness, muscle weakness, and ataxia.
Lithium level > 1.2 mmol/L may be toxic in older patients.
Increased levels may occur in sodium depletion, e.g. associated with diuretics.
Measurement of uncertainty
Frequency of measurement
Daily