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Salicylate (aspirin) blood level

Toxicology

Acetylsalicylic acid levelASAAspirin levelSAL

Review status

Currently under review

Pending specialist review and validation.

What it shows

This test measures the amount of salicylate in your blood. Salicylates are the active breakdown products of aspirin and related medicines, including some pain relievers, cold remedies, topical creams, and oil of wintergreen. The level reflects how much salicylate is in your system at the time of the blood draw.

Clinicians use this test to evaluate possible exposure or overdose, to monitor treatment if aspirin is being used for medical therapy, and to help explain symptoms that might be due to salicylate effects. Because absorption can be delayed by certain formulations, levels may be repeated to track trends over time.

Why it matters

Salicylates affect the brain, lungs, and metabolism. When levels rise too high, they can cause symptoms such as nausea, vomiting, ringing in the ears, rapid breathing, dizziness, or confusion. Serious poisoning can lead to dehydration and changes in acid-base balance. The test helps your care team confirm exposure, gauge severity, and plan treatment.

It is commonly ordered when there is a suspected ingestion, uncertain timing or amount taken, or ongoing symptoms after using aspirin-containing products. It is also helpful in people at higher risk of complications, such as children, older adults, and those with kidney problems or chronic aspirin use. Results guide decisions about observation, repeat testing, and specific therapies.

Understanding your results

Your result is interpreted together with your symptoms, the time since the last dose, other lab values, and how you are feeling. Some aspirin products are absorbed slowly, so an early level may not reflect the peak. Doctors often repeat the test to see whether the level is stable, rising, or falling, and whether it matches your clinical picture.

If the level is higher than expected or is rising, your team may extend observation, repeat levels, and adjust treatment. If you feel unwell despite a level that is not very high, your clinicians will look at other clues such as breathing pattern and blood tests to guide care. Ask your clinician when to return for rechecks and which warning symptoms should prompt urgent attention.

Reference ranges

0.71.45 mmol/L
All sexes
0 days – 18 years
1.12.2 mmol/L
All sexes
18 years – 150 years

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

Factors that could impact Salicylate (aspirin) blood level

  • Timing of the sample

    Levels taken soon after ingestion can underestimate exposure because absorption may be delayed. Repeat levels are often needed until the trend is clearly decreasing and your symptoms are improving.

  • Formulation and route

    Enteric-coated tablets, sustained-release products, topical salicylates, and oil of wintergreen can absorb slowly or unpredictably, leading to delayed peaks that change how results are interpreted.

  • Kidney function and acid-base balance

    Salicylates are cleared by the kidneys. Reduced kidney function or acid-base changes can raise levels or increase toxicity at a given level, so clinicians consider these factors when interpreting results.

  • Co-ingestants and interactions

    Other medicines or substances can alter absorption or elimination. Antacids, activated charcoal, diuretics, and certain antibiotics may affect measured levels or clinical effects.

  • Chronic use and special populations

    Older adults, children, and pregnant patients may show symptoms at lower levels or develop toxicity gradually with repeated dosing. Clinicians interpret results cautiously in these groups.

  • Specimen handling

    Proper collection and timely processing support accurate results. Let the lab know about recent treatments, such as activated charcoal or bicarbonate therapy, which can influence interpretation.

2026

References

  1. McGill University Health Centre. (2015, July 02). Salicylate (Task CD 317268). Laboratory reference ranges.
  2. American College of Medical Toxicology. (2015). Guidance document: Management priorities in salicylate toxicity. Journal of Medical Toxicology, 11(2), 149-152.
  3. EXTRIP Workgroup. (2015). Recommendations on the use of extracorporeal treatments in salicylate poisoning. Clinical Toxicology, 53(2), 95-105.
  4. Juurlink, D. N. (2013). The spectrum of salicylate toxicity. CMAJ, 185(6), 494-502.