At a Glance
Why Get Tested?
To detect salicylate overdose, to help evaluate its severity and monitor its resolution; sometimes to monitor for an overdose if you regularly use prescription-strength salicylates
When to Get Tested?
When you have symptoms such as nausea, hyperventilation, ringing in the ears (tinnitus), or confusion that may be from taking too much aspirin or medications with salicylate ingredients; when it is suspected that your child may have ingested a significant quantity of a salicylate; at regular intervals when monitoring an overdose; sometimes on a regular basis when you take a prescription salicylate for rheumatoid arthritis or other autoimmune disorder
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None, but your doctor may ask when you last took a salicylate and the amount taken. If you regularly take a prescription salicylate, your doctor may want to collect blood just prior to your next dose (trough level). Tell your doctor about any other medications you are taking.
The Test Sample
What is being tested?
Salicylates are a group of drugs, including aspirin, available as both prescription and non-prescription (over-the-counter) medications. They are often used to relieve pain and inflammation, to reduce fever, and to prevent excessive clotting. Salicylate testing measures the concentration in the blood to detect and/or monitor an overdose (salicylate poisoning).
Aspirin is the most common salicylate, but there are others, including methyl salicylate, which is found as oil of wintergreen in some muscle ache creams. Methyl salicylate creams and topical forms of aspirin are absorbed into the body through the skin. After oral forms of salicylates are ingested, they are converted to salicylic acid, absorbed in the stomach and small intestine and transferred into the blood stream. They are metabolized by the liver and eliminated from the body in the urine within a few hours.
With single, normal doses, blood concentrations typically peak in about 2 hours, but this may be delayed for 12 hours or more with "enteric-coated" or "sustained-release" preparations. If too much salicylate is ingested (acute toxicity with a large ingestion) or too much is taken over time (chronic toxicity), and/or if the body's ability to remove the salicylates is impaired, then signs and symptoms associated with toxicity will begin to emerge. The ability to remove salicylates efficiently is affected by the body's blood and urine pH (acidity/alkalinity) and by kidney function.
Over-the counter salicylates are used as needed or regularly to reduce pain, fever, and inflammation. Low doses of aspirin may be taken on a regular basis to reduce the chance of inappropriate blood clotting (thrombosis), heart attack, or stroke in people who have a high risk. Aspirin may also be used to reduce the risk of complications in someone who is having a heart attack, or who recently experienced one. Aspirin is also used in patients with myeloproliferative neoplasms (e.g., polycythemia vera, essential thrombocythemia). Uncommonly, prescription-strength aspirin may be used to relieve symptoms of rheumatoid arthritis (RA) and osteoarthritis as well as symptoms of autoimmune disorders such as lupus.
When used with care and following dosing directions, therapeutic doses of salicylates are safe and effective for most adults. Excessive amounts of salicylates, however, can be toxic, affecting breathing and disrupting the body's acid-base balance. In severe cases, toxicity can cause convulsions, coma, and even death.
Adults can run into trouble with salicylates when they unknowingly combine multiple products that contain them. Many over-the-counter medications include a salicylate as one of the ingredients. An individual who is unaware of the ingredients can mistakenly take more than one of these drugs together, resulting in a cumulative effect and a high amount of ingested salicylate. Widespread and easy availability of salicylate-containing medications can also mislead some to think that it is very safe and that "more is better." An overdose can occur when someone has pain that is not relieved with an initial dose and, unaware of the danger, takes more than the recommended dose and/or takes additional doses too frequently. In the elderly, these scenarios can especially be a problem because underlying conditions and general health status can decrease the ability to eliminate salicylates.
Aspirin is not recommended for use in children and adolescents because of the risk of developing Reye syndrome, a disease characterized by acute brain damage and liver dysfunction that can be fatal. Though youth are not routinely given aspirin, they may become poisoned through accidental or intentional ingestion. Topical creams that contain methyl salicylate or other salicylates are of special concern as they contain very high doses.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed, but the doctor may ask when a salicylate was last ingested and the amount taken. To accurately interpret results, blood samples are usually drawn at least 4 hours after ingestion. If a person regularly takes a prescription salicylate, the doctor may want to collect blood just prior to the next dose (trough level).
Ask a Laboratory Scientist
Form temporarily unavailable
Due to a dramatic increase in the number of questions submitted to the volunteer laboratory scientists who respond to our users, we have had to limit the number of questions that can be submitted each day. Unfortunately, we have reached that limit today and are unable to accept your inquiry now. We understand that your questions are vital to your health and peace of mind, and recommend instead that you speak with your doctor or another healthcare professional. We apologize for this inconvenience.
This was not an easy step for us to take, as the volunteers on the response team are dedicated to the work they do and are often inspired by the help they can provide. We are actively seeking to expand our capability so that we can again accept and answer all user questions. We will accept and respond to the same limited number of questions tomorrow, but expect to resume the service, 24/7, as soon as possible.
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Waseem, M. et. al. (Updated 2011 October 27). Salicylate Toxicity. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/1009987-overview through http://emedicine.medscape.com. Accessed January 2013.
(© 1995–2013). Salicylate, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8480 through http://www.mayomedicallaboratories.com. Accessed January 2013.
O'Malley, G. (Modified 2012 February). Aspirin and Other Salicylate Poisoning (Salicylism). [On-line information]. Available online through http://www.merckmanuals.com. Accessed January 2013.
Frithsen, I. and Simpson, W. (2010 February 1). Recognition and Management of Acute Medication Poisoning. Am Fam Physician. 2010 Feb 1;81(3):316-323. [On-line information]. Available online at http://www.aafp.org/afp/2010/0201/p316.html through http://www.aafp.org. Accessed January 2013.
Glisson, J. et. al. (Updated 2011 ). Current Management of Salicylate-induced Pulmonary Edema. Medscape Today News from South Med J. 2011;104(3):225-232. [On-line information]. Available online at http://www.medscape.com/viewarticle/738265 through http://www.medscape.com. Accessed January 2013.
(2009 Fall). Salicylates. California Poison Control System v7(4) [On-line information]. Available online at http://www.calpoison.org/hcp/2009/callusvol7no4.htm through http://www.calpoison.org. Accessed January 2013.
Perez, E. (Updated 1012 February 16). Methyl salicylate overdose. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002683.htm. Accessed January 2013.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 367.
Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 593-594.
McPherson, R. and Pincus, M. (© 2011). Henry's Clinical Diagnosis and Management by Laboratory Methods 22nd Edition: Elsevier Saunders, Philadelphia, PA. Pp 352-353.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 1436-1437.
Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. 4th edition, St. Louis: Elsevier Saunders; 2006, Pp 1288, 1306-1308.
Dargan P, Wallace C I, Jones, A L. An evidence based flowchart to guide the management of acute salicylate (aspirin) overdose. Emerg Med J 2002;19:206–209. Available online at: http://www.rheumatology.org/practice/clinical/patients/medications/nsaids.asp through http://www.rheumatology.org. Accessed Feb 2013.