Salicylate (Aspirin Level)
Measures salicylate, the form aspirin takes in your blood. It is mainly used when too much aspirin or a similar product may have been taken.
AI-verified against cited sources. Awaiting expert reviewLOINC 4024-6
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What it is
Aspirin and related products break down into salicylate in your body, and this test measures it in your blood. It is most often ordered in an emergency department when someone may have taken too much aspirin or another product that contains salicylate, such as oil of wintergreen, some stomach remedies with bismuth subsalicylate, or some pain creams. It is also sometimes used to check levels in people taking high-dose salicylate for inflammation. Levels can keep rising for hours after a large dose, so repeat tests are common.
Why it matters
Too much salicylate can upset the body's acid balance and cause ringing in the ears, nausea, fast breathing, confusion and, in severe cases, seizures or coma. A single level can be misleading, because it can be low or not measurable soon after a large dose and rise later. Care teams usually repeat the test over several hours and look at other blood tests, such as acid-base, potassium and kidney function. The result is used to guide care along with how the person looks and feels.
If it’s low
A low or not-measurable level is expected if you haven't had aspirin or a similar product recently, and is also common with the low daily doses used for heart protection. It can also be low soon after a large dose, before the drug has been fully absorbed, which is why doctors often repeat the test.
Common causes
- No recent aspirin or salicylate product
- Low-dose aspirin
- Very soon after a large dose, before absorption is complete, since delayed peaks can occur
What can help
- If an overdose is possible, ask whether the test should be repeated rather than relying on one low result
If it’s high
A high result means a large amount of salicylate is in the blood. A level of about 15 to 30 mg/dL has been reported as the therapeutic range for people taking salicylate as a medicine, and ringing in the ears often begins around 30 mg/dL. Higher levels are linked to fast breathing, vomiting, confusion and acid-base changes, and are treated in a hospital.
Common causes
- Taking more aspirin or another salicylate product than intended, including by accident
- Using several products that contain salicylate at once, such as aspirin, bismuth subsalicylate and oil of wintergreen
- Long-term high-dose aspirin therapy
- Reduced kidney function, which slows removal
- Large amounts of methyl salicylate used on broken skin or under wraps
What can help
- If you think you or someone else took too much salicylate, contact Poison Control or emergency services right away, even if there are no symptoms yet
- Keep a list of the medicines and creams you use that contain aspirin or salicylate
- Ask your clinician whether your kidney function should be checked
What can affect your result
- Time since the dose: levels can be low soon after a large dose and peak later
- The amount taken and the number of products that contain salicylate
- Kidney function, and the way removal slows as levels rise
- Extended-release or enteric-coated products, which can delay the peak
- Many products contain salicylates (aspirin, bismuth subsalicylate, oil of wintergreen, some pain creams and combination pain relievers). All are measured as salicylate.
- A sample taken soon after a large dose can be low or not measurable, with a delayed peak later.
- Labs print mg/dL, mg/L or mmol/L, and mixing these up can cause errors of ten-fold or more. Check the unit on your report.
In suspected poisoning, samples are repeated over several hours, because the level can rise after the first draw. After a large dose, levels can keep rising for several hours and fall slowly, because the body's removal pathways become saturated as levels climb.
When to talk to a clinician
If you may have taken too much aspirin or a product that contains salicylate, or someone has ringing in the ears, nausea or vomiting, fast breathing, confusion or unusual sleepiness after taking it, call Poison Control (in the US, 1-800-222-1222) or 911 or your local emergency number right away. Don't wait for symptoms, because they can appear hours later.
Questions you could ask
- Which of my medicines or creams contain salicylate?
- Which product might this have come from, and could I still be absorbing it?
- Do I need repeat levels or other blood tests?
- Should my kidney function be checked?
- Is a single level enough, or should it be repeated?
Questions people ask
Is a salicylate test the same as an aspirin test?
In practice, yes. Aspirin breaks down into salicylate, which is what the test measures. It also measures salicylate from other products, such as bismuth subsalicylate and oil of wintergreen.
Why do doctors repeat the test?
After a large dose, salicylate can be slow to reach the blood, and levels can keep climbing for hours. A first result may be low or not measurable, so repeat tests show whether the level is rising or falling.
How do I convert mg/dL to mmol/L?
Multiply mg/dL by 0.0724, so 30 mg/dL is about 2.2 mmol/L. To go the other way, multiply mmol/L by 13.8. To convert between mg/dL and mg/L, multiply by 10 or divide by 10.
Show the science and sources
Units
- 1 mg/dL = 1 mg/dL
- 1 mg/dL = 10 mg/L
- 1 mg/dL = 0.0724 mmol/L
- 1 mg/dL = 72.4 µmol/L
Open the Salicylate unit converter
For clinicians and researchers
Salicylate is measured in serum or plasma. All forms (acetylsalicylate, methyl salicylate, bismuth subsalicylate) are metabolized to salicylate, so the test reflects exposure from any source. At usual doses elimination is first-order, but the glucuronidation, oxidation and glycine conjugation pathways saturate as levels rise, shifting to zero-order kinetics and lengthening the half-life. Absorption can be erratic and delayed after large ingestions, so serial levels are used, and unlike acetaminophen no reliable nomogram exists. A 2025 emergency medicine review reports a therapeutic range of 15 to 30 mg/dL, with tinnitus averaging about 30 mg/dL (as low as 19.6). As summarized there, the EXTRIP workgroup recommends extracorporeal treatment for a salicylate concentration above 100 mg/dL (above 90 with impaired kidney function), altered mental status, hypoxia, or failure of standard care, and suggests it above 90 mg/dL (above 80 with impaired kidney function) or pH below 7.20. Fatalities have occurred below 100 mg/dL, so the concentration alone does not decide treatment. One analyzer read chloride falsely high at salicylate above 60 mg/dL, which can mask the anion gap. A 2026 survey of 411 US hospitals found a median critical limit of 30 mg/dL (range 20 to 100). 1 mmol/L equals 13.81 mg/dL (molecular weight 138.12).
LOINC 4024-6 (primary), 14909-6, 35597-4, 46978-3. Specimen: serum-or-plasma.
Sources
- Drug Critical Limits for Urgent Physician Notification, Clinical Pharmacology & Therapeutics (2026)
- Acute Salicylate Toxicity: A Narrative Review for Emergency Clinicians, Cureus (2025)
- Salicylates Level, MedlinePlus (National Library of Medicine)
- Salicylic Acid (PubChem CID 338), PubChem, National Library of Medicine
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.