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Blood Test Tracker

Arsenic, Blood

Measures arsenic in your blood right now. It reflects very recent exposure, because arsenic leaves the blood quickly.

AI-verified against cited sources. Awaiting expert reviewLOINC 5583-0

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What it is

Arsenic is a natural element found in soil, rock and some drinking water. This test measures the arsenic in a sample of whole blood. Your body clears arsenic from the blood within hours to a few days, mostly into the urine. So a blood level shows only what is in your blood now, and it can be normal even when the urine level is still high. For that reason, urine testing is usually preferred for checking arsenic exposure.

Why it matters

Arsenic in drinking water, food or some workplaces can, over many years, affect the skin, nerves, heart and blood vessels, and is linked to a higher chance of some cancers. A blood test can help soon after a suspected exposure. It can't tell you whether arsenic will affect your health. Your clinician reads it together with your exposure history and symptoms.

If it’s high

A result above your lab's limit means more arsenic than usual was in your blood when it was drawn. A recent meal of seafood can be a harmless reason, because seafood contains a form of arsenic that is much less harmful. Other causes are exposure from water or work, or swallowing or breathing in an arsenic-containing product. A urine test, with speciation if needed, can show which form is involved. Your clinician can put the number in context.

Common causes

  • A recent seafood or seaweed meal (mostly the less toxic organic arsenic)
  • Drinking water from a private well or an area with naturally high arsenic
  • Work with arsenic, such as smelting, wood treating or pesticide use
  • Swallowing or breathing in arsenic compounds, for example from pesticides, treated wood or a contaminated product

What can help

  • Ask your clinician whether a urine test (with speciation if needed) would add useful information
  • Talk through possible sources with your clinician, such as well water, your job, hobbies or treated wood
  • If you have a private well, ask your local health department how to have the water tested

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: up to 13 µg/L. Source: Mayo Clinic Laboratories (catalog mirrored at testcatalog.org), ATSDR (archived copy).

What can affect your result

  • How recently you were exposed, since blood levels fall within hours to days
  • Seafood or seaweed eaten shortly before the draw
  • Recent contrast dye (gadolinium or iodine)
  • The type of collection tube, which should be metal-free
  • Gadolinium or iodine contrast dye can interfere with this kind of metal test. Mayo advises not collecting a sample for 96 hours after a dose.
  • Recent seafood or seaweed can add mostly harmless organic arsenic to a total result. Follow your lab's instructions on how long to avoid them.
  • Use the metal-free tube your lab provides. Mayo uses a royal-blue-top EDTA tube and sends the blood in the original tube.

Reflects very recent exposure, from hours to a few days, because the body clears arsenic from the blood quickly.

When to talk to a clinician

Contact your clinician promptly if your result is well above your lab's range and you have symptoms such as nausea, vomiting, belly pain, numbness or tingling in your hands or feet, or new skin changes. If you may have swallowed or breathed in a large amount of arsenic, call Poison Control at 1-800-222-1222 in the US, or your local emergency number, right away.

Questions you could ask

  • Is a blood or a urine test better for my situation?
  • How does my lab's range apply to my result?
  • Could a recent seafood meal, my water or my job explain this result?
  • Would a urine test, with arsenic speciation, help sort out the source?
  • Should we repeat this test, and when?

Questions people ask

Why is a urine test usually preferred over a blood test for arsenic?

Arsenic leaves the blood quickly and is cleared mainly in the urine. Blood levels can look normal even when urine levels are still high, so urine gives a better picture of recent exposure.

Is 13 µg/L the same as 13 ng/mL?

Yes. One µg/L equals one ng/mL, so both units give the same number. To convert to nmol/L, multiply µg/L by about 13.35.

Show the science and sources

Units

  • 1 µg/L = 1 µg/L
  • 1 µg/L = 1 ng/mL
  • 1 µg/L = 13.35 nmol/L
  • 1 µg/L = 0.1 µg/dL

Open the Arsenic (blood) unit converter

For clinicians and researchers

Mayo Clinic Laboratories measures arsenic in whole blood by ICP-MS/MS in a metal-free EDTA tube. Inorganic arsenic has a half-life of about 10 hours in humans, and the half-life of ingested fish arsenic is under 20 hours, with urinary clearance in about 48 hours. Arsenic is also taken up by red blood cells and methylated in the liver. Because it clears so quickly, ATSDR notes that blood levels may be normal while urine levels remain markedly elevated, and that blood is less useful than urine for following acute poisoning. ATSDR gives blood arsenic as normally under about 1 µg/dL in unexposed people. The test measures total arsenic and cannot separate toxic inorganic arsenic from seafood arsenic. Gadolinium and iodine contrast interfere with ICP-MS metal assays. No critical value is published by Mayo for blood arsenic.

LOINC 5583-0 (primary), 15114-2. Specimen: whole-blood.

Sources

  1. Heavy Metals Screen with Demographics, Blood (Mayo test HMDB), Mayo Clinic Laboratories (catalog mirrored at testcatalog.org)
  2. Arsenic Toxicity: Clinical Assessment (Case Studies in Environmental Medicine), ATSDR (archived copy)
  3. Arsenic Toxicity: Biologic Fate (Case Studies in Environmental Medicine), ATSDR (archived copy)
  4. Arsenic (PubChem compound 5359596), 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.

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