Test Catalog

Test ID: LITH    
Lithium, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Monitoring therapy of patients with bipolar disorders, including recurrent episodes of mania and depression


Evaluating lithium toxicity

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Lithium alters the intraneuronal metabolism of catecholamines by an unknown mechanism. It is used to suppress the manic phase of manic-depressive psychosis.


Lithium is distributed throughout the total water spaces of the body and is excreted primarily by the kidney.


Toxicity from lithium salts leads to ataxia, slurred speech, and confusion. Since the concentration of lithium in the serum varies with the time after the dose, blood for lithium determination should be drawn at a standard time, preferably 8 to 12 hours after the last dose (trough values).

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Therapeutic: 0.5-1.2 mmol/L (trough concentration)

Critical value: >1.6 mmol/L

There is no relationship between peak concentration and degree of intoxication.

Interpretation Provides information to assist in interpretation of the test results

The therapeutic range for lithium has been established at 0.5 to 1.2 mmol/L. Within this range, most people will respond to the drug without symptoms of toxicity. However, response and side effects are individual. Lithium concentrations and side effects can increase with the loss of salt and water from the body, which can occur with a salt-free diet, excessive sweating, or an illness that causes vomiting and diarrhea. A variety of prescribed drugs, over-the-counter medications, and supplements can also increase, decrease, or interfere with the concentrations of lithium.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Judd LL: The therapeutic use of psychotropic medications: lithium and other mood-normalizing medications. In Harrison's Principles of Internal Medicine. 12th edition. Edited by JD Wilson, E Braunwald, KJ Isselbacher, et al. New York, McGraw-Hill Book Company, 1991, pp 2141-2143

2. Gelenberg AJ, Kane JM, Kekller MB, et al: Comparison of standard and low serum levels of lithium for maintenance treatment of bipolar disorder. N Engl J Med 1989;321:1489-1493

3. Lithium Product Monograph, Physicians' Desk Reference (PDR). 61st edition. Montvale, NJ: Thomson PDR, 2007