TLB - Clinical: Thallium, Blood

Test Catalog

Test Name

Test ID: TLB    
Thallium, Blood

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

Detecting toxic thallium exposure

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

Thallium is a by-product of lead smelting. The clinical interest in thallium derives primarily from its use as a rodenticide since this is the most frequent route of human exposure.


Thallium is rapidly absorbed via ingestion, inhalation, skin contact, and through the mucous membranes of the mouth, gastrointestinal tract, and lungs. It is considered to be as toxic as lead and mercury, with similar sites of action.


The mechanism of action of thallium is:

-Competition with potassium at cell receptors to affect ion pumps

-Inhibition of DNA synthesis

-Binds to sulfhydryl groups on proteins in neural axons

-Concentrates in renal tubular cells and reacts with protein to cause necrosis


Patients exposed to high doses of thallium (>1 g) present with alopecia (hair loss), peripheral neuropathy and seizures, and renal failure.

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.

0-1 ng/mL

Reference values apply to all ages.

Interpretation Provides information to assist in interpretation of the test results

Normal blood concentrations are <1 ng/mL.


Significant exposure is associated with thallium in blood >10 ng/mL, and blood concentrations as high as 50 ng/mL. The long-term sequelae from such an exposure is poor.

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

High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen should not be collected for 96 hours.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Pelcloval D, Urbanl, P, Ridsonl P, et al: Two-year follow-up of two patients after severe thallium intoxication. Hum Exper Toxicol 2009;28:263-272

2. Zhao G, Ding M, Zhang B, et al: Clinical manifestations and management of acute thallium poisoning. Eur Neurol 2008;60:292-297

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test