Test Catalog

Test ID: SALCA    
Salicylate, Serum

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

Assessing toxicity


This test is not useful for assessing low-dose aspirin therapy

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

Therapeutic salicylates include, among others, salicylic acid, sodium salicylate, methyl salicylate (oil of wintergreen), and acetylsalicylic acid (aspirin).


Aspirin is an analgesic, antipyretic, anti-inflammatory drug contained in a large number of preparations. Aspirin is rapidly hydrolyzed by hepatic and blood esterases to the pharmacologically active intermediate, salicylic acid, which has a dose-dependent serum half-life ranging from 3 to 20 hours.


Stimulation of the respiratory center in the central nervous system and uncoupling of oxidative phosphorylation are direct effects of salicylate that lead to many of the toxic symptoms observed in overdose situations.


Symptoms of salicylate toxicity can include nausea, vomiting, tinnitus, headache, hyperpnea, confusion, hyperthermia, slurred speech, and convulsions. Acid-base disturbances such as compensated respiratory alkalosis (mild toxicity) and metabolic acidosis with increased anion gap (severe toxicity) are commonplace.

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: <30.0 mg/dL

Critical value: > or =50.0 mg/dL

Interpretation Provides information to assist in interpretation of the test results

Therapeutic concentrations for antipyretic/analgesic are 3.0 to 10.0 mg/dL, while concentrations between 1.5 and 30 mg/dL are for anti-inflammatory effect and treatment of rheumatic fever.


Toxic concentrations are 50.0 mg/dL or higher.

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

This test is not intended for use with low-dose aspirin therapy. Most patients on low daily doses of aspirin for cardiovascular prophylaxis will have serum concentrations near or below the lower limit of the analytical range.

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

1. Done AK: Aspirin overdosage: incidence, diagnosis, and management. Pediatrics 1978;62:890-897

2. Medical Toxicology, Third edition, Edited by RC Dart. 2004 pp 1811