Lithium

Specimen

Serum collected 12 hours after the previous (evening) dose.

Units

mmol/L

Reference Range

GUIDELINES FOR INTERPRETATION OF LITHIUM LEVELS

(for samples taken 12 hours after the last dose)

• Therapeutic range : 0.4 – 1.0 mmol/L
• Warning range : 1.1 – 1.5 mmol/L
• Toxic range : 1.6 – 2.0 mmol/L
• SEVERE TOXICITY : >2.1 mmol/L (Emergency treatment required)

Test Usage

Although effective as an anti-depressant, this drug has a very narrow therapeutic window, and levels > 1.4 mmol/l lead to an increased risk of oliguria and ARF, which in turn, since 95% of lithium is eliminated by the kidney, result in a further increase in circulating levels. Monitoring should initially be every 2 to 3 days until a steady state has been reached (unless levels of > 1.1 mmol/l are detected), then weekly for the first month, monthly during the next 6 months and thereafter at 3-monthly intervals. NB Alterations in lithium levels often occur with intercurrent illness.

Lithium is usually given daily in a divided dose of sustained release capsules, although increasingly, a single dose is being prescribed. Lithium levels should be determined 12 hours after the previous (evening) dose.

Since lithium therapy can cause thyroid dysfunction, it is recommended that patients on this drug should have their thyroid function tests checked every 6 months.

Availability

Local

Turnaround Time

1 day

Can be added on to an existing request up to 4 days following sample receipt