Lithium

Order Code

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2128

Preferred Specimen

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Collect 2 mL Serum. Let the SST clot upright for at least 30 minutes, then centrifuge the sample within 2 hours of collection. Refrigerate the processed specimen.

Container Type

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Serum Separator Tube

Alternate Specimen Requirements

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Acceptable alternatives include:

2 mL Serum collected in a plain red-top tube is acceptable. Allow it to clot upright for at least 60 minutes, then centrifuge and transfer the serum into a plastic transport tube within 2 hours. Clearly label the tube “Serum from Plain Red-Top Tube” and Refrigerate.

Minimum Volume

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• 0.5 mL Serum

Transport Temperature

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Refrigerated

Expected Turnaround Time

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1 Day

Specimen Stability

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• Room Temperature: 5 Days
• Refrigerated: 1 Week
• Frozen: 6 Months

Methodology

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Roche COBAS colorimetric method using a substituted porphyrin compound.

Rejection Criteria

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Hemolysis

Lithium Heparin Plasma

Overview

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Lithium is primarily used in managing bipolar disorder, particularly during the manic phase, to lessen the severity and frequency of episodes. It is also effective in treating bipolar depression. Because lithium has a narrow therapeutic window and carries a risk of toxicity, careful monitoring of both serum levels and the patient’s clinical condition is essential.

Clinical Significance

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Used for therapeutic drug monitoring to evaluate the drug’s effectiveness, detect signs of toxicity, monitor dosage adjustments, or identify possible noncompliance.
It is recommended to check lithium levels twice weekly during the early phase of treatment until the appropriate dose is achieved.
Once the patient’s levels are stable, monitoring every two months is advised.

Additional Information

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• Half-life: 18–24 hours (up to 36 hours in elderly or renally impaired patients)
• Volume of Distribution: 0.7–1.0 L/kg
• Protein Binding: 0%
• Bioavailability: 100%
• Elimination: >98% excreted unchanged by the kidneys

Lithium, usually taken as lithium carbonate or lithium citrate, is a psychoactive drug used for manic-depressive disorders. These oral forms are fully absorbed and bioavailable, with peak serum levels occurring 1–2 hours after immediate-release doses and 4–12 hours after extended-release doses.
Lithium is excreted by the kidneys, filtered through the glomerulus, and actively reabsorbed at the proximal tubule—similar to sodium. Because of this, drug and food interactions that alter sodium or fluid balance can affect lithium levels. Clearance is reduced in cases of renal impairment, dehydration, or hyponatremia. Patients should maintain a consistent sodium intake while on lithium.

Toxicity

• Acute lithium toxicity often causes vomiting, diarrhea, and impaired kidney function due to dehydration. Neurological symptoms like sluggishness, tremors, or seizures can appear later. High lithium levels confirm the diagnosis but may not always match symptom severity.
• Chronic lithium toxicity typically shows a closer correlation between lithium levels and symptoms. It can develop from dehydration, illness, or drug interactions (especially with NSAIDs or ACE inhibitors). Neurological symptoms are often the first signs.

Drug Interactions
Levels/effects of lithium may increase with:
Almotriptan, Alosetron, Amphetamines, ACE inhibitors, Angiotensin II receptor blockers, Buspirone, Calcium channel blockers (non-dihydropyridine), Carbamazepine, Cyclobenzaprine, Dapoxetine, Desmopressin, Dextromethorphan, Eletriptan, Loop diuretics, Methadone, Metronidazole, NSAIDs (systemic and topical), Ondansetron, Opioids, Phenytoin, Thiazide diuretics, Tricyclic antidepressants, Serotonergic drugs, and St. John’s Wort, among others.

Levels/effects of lithium may decrease with:
Caffeine and caffeine-containing products, Calcitonin, Carbonic anhydrase inhibitors, Sodium bicarbonate, Sodium chloride, Sodium polystyrene sulfonate, Theophylline derivatives, and St. John’s Wort.

Limitations

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Lithium toxicity, including serious neurotoxic effects, can occur even when serum lithium levels appear normal.
In acute intoxication, lithium levels may rise sharply without immediate neurological symptoms, as lithium enters neurons slowly (Stern, 1995).

References

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Diagnostic Role

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Used for identifying acute toxicity.

Test Setup Days

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Monday through Friday PM shift

CPT

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80178 LOINC: 3719-2

Reference Range

0.60-1.20 MEQ/L

UNIT CODE	UNIT CODE NAME	ANALYTE	GENDER	AGE	REFERENCE RANGE	Units of Measure
2128	LITHIUM	LI	NOT SPECIFIED	ALL	0.60–1.20	MEQ/L
2128	LITHIUM	LI	MALE	ALL	0.60–1.20	MEQ/L
2128	LITHIUM	LI	FEMALE	ALL	0.60–1.20	MEQ/L