Test Catalog

Test ID: TLB    
Thallium, Blood

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

Detecting toxic thallium exposure in whole blood specimens

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.

0-17 years: not established

> or =18 years: <2 ng/mL 

Interpretation Provides information to assist in interpretation of the test results

Normal blood concentrations are less than 1 ng/mL.


Significant exposure is associated with thallium concentrations in blood greater than 10 ng/mL, and 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

No significant cautionary statements.

Clinical Reference Recommendations for 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 Library of PDFs including pertinent information and forms related to the test