Skip to content
Blood Test Tracker

Arsenic, 24-Hour Urine

The total arsenic your body cleared in urine over a full day, a standard way to check for recent arsenic exposure.

AI-verified against cited sources. Awaiting expert reviewLOINC 5587-1

Check your result

Sex (optional)

Type your result to see where it falls.

Nothing you type here leaves your browser.

What it is

Arsenic is a natural element found in soil, rock and some drinking water. It also shows up in certain jobs, wood treatments and foods. Your body clears most arsenic through the urine within a few days, so a urine test shows recent exposure. This test adds up all the arsenic in every bit of urine you collect over 24 hours. A full day of urine gives a steadier picture than a single sample, which can swing with how much you drank. The result is total arsenic, so it counts harmless seafood arsenic along with the toxic forms.

Why it matters

Long-term exposure to inorganic arsenic, mostly from drinking water or some workplaces, is linked to skin changes, nerve and heart problems and a higher chance of some cancers. This test shows how much arsenic is passing through your body. It can't tell you whether it will affect your health. Your clinician reads it together with your diet, water source, job and symptoms.

If it’s high

A result above your lab's limit means more arsenic than usual left your body that day. The most common reason is eating seafood or seaweed, which contain a form of arsenic that is much less harmful. A total arsenic result can't tell the forms apart, so labs often run a second test (called speciation) when the number is high. Well water, some workplaces and some remedies can also raise it. Your clinician can put the number in context.

Common causes

  • Eating fish, shellfish or seaweed in the last few days (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
  • Sawdust or smoke from burning wood treated with arsenic
  • Some folk, imported or alternative remedies

What can help

  • Ask your clinician whether to follow up with an arsenic speciation test, or a repeat after a few days without seafood
  • Talk through possible sources with your clinician, such as well water, your job, hobbies, wood stoves 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 35 µg/24 h. Source: Mayo Clinic Laboratories (catalog mirrored at testcatalog.org), ATSDR (archived copy), Journal of Medical Toxicology.

What can affect your result

  • Seafood and seaweed in the 2 days before and during the collection
  • Recent contrast dye (gadolinium or iodine), which can disrupt the measurement for about 4 days
  • Whether the whole 24 hours of urine was collected
  • Your water source, diet and job
  • Age: Mayo has only set an adult range (18 and older)
  • Seafood and seaweed in the 2 days before and during the collection can add harmless organic arsenic to the total. Mayo asks for no seafood for 48 hours before the collection.
  • Gadolinium or iodine contrast dye can interfere with this kind of metal test. Mayo advises not collecting urine for 96 hours after a dose.
  • Use the clean plastic container your lab gives you. Mayo specifies no metal cap and no glued insert, because metal can contaminate the sample.
  • Missed urine makes the 24-hour total look lower than it is.
  • Urine collected after taking a chelating medicine (a "provoked" test) has no valid reference range and is not recommended for diagnosis.

A full 24-hour collection. Start by emptying your bladder and throwing that urine away, note the time, then collect all of your urine for the next 24 hours. Your lab will give you a container and exact steps. Shows arsenic taken in over roughly the last few days. Most of a single low-level dose leaves in the urine within a few days.

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

  • What should I avoid eating or doing before a 24-hour urine collection?
  • How does my lab's range apply to my result?
  • Could seafood, my drinking water or my job explain this result?
  • Should we repeat the test after a few days without seafood, or ask for arsenic speciation?
  • Should we check anything else alongside this, such as a blood count or kidney and liver tests?

Questions people ask

Do I need to avoid seafood before this test?

Yes, usually. Fish, shellfish and seaweed contain an organic form of arsenic that is mostly harmless but adds to the total. Mayo asks for no seafood for 48 hours before the collection. Follow the instructions from your own lab.

Why does my report show two numbers, one in µg/L and one in µg/24 h?

The lab first measures how concentrated the arsenic is in your pooled urine (µg/L). It then multiplies by the total volume you collected to get the amount for the day (µg/24 h). This page is about the 24-hour amount.

Is a 24-hour sample better than a single urine sample?

ATSDR calls a 24-hour collection the best specimen because it reflects the true amount of arsenic leaving the body. A single sample can still help, especially when it is paired with a creatinine measurement.

Show the science and sources

Units

  • 1 µg/24 h = 1 µg/24 h
  • 1 µg/24 h = 13.35 nmol/24 h
  • 1 µg/24 h = 0.01335 µmol/24 h

Open the Arsenic (24-h urine) unit converter

For clinicians and researchers

Total urinary arsenic includes inorganic arsenic (arsenite and arsenate), its methylated metabolites (MMA and DMA) and organic seafood arsenic such as arsenobetaine, which is excreted unchanged within about 48 hours. Only the first two groups are considered toxic. Mayo measures total arsenic by ICP-MS/MS and reflexes to speciation when the concentration is 10 mcg/L or more. Its speciated "toxic arsenic" limit of <35 mcg/L is based on the ACGIH Biological Exposure Index, which excludes organic arsenic. ATSDR considers total urinary arsenic above 100 µg/L abnormal, notes that seafood can raise it by thousands of µg/L, and names a 24-hour collection with creatinine as the best specimen. The half-life of inorganic arsenic in humans is about 10 hours, and urinary levels can fall quickly in the first 24 to 48 hours after an acute exposure. Gadolinium and iodine contrast interfere with ICP-MS metal assays. Chelator-provoked urine has no established reference range (Ruha 2013). Mayo also reports the arsenic concentration of the pooled urine in µg/L (LOINC 21074-0); that number is not covered by this marker, which holds the 24-hour amount.

LOINC 5587-1 (primary), 34244-4. Specimen: urine-24h.

Sources

  1. Arsenic with Reflex, 24 Hour, Urine (Mayo test ASU24), Mayo Clinic Laboratories (catalog mirrored at testcatalog.org)
  2. Heavy Metals Screen, with Reflex, 24 Hour, Urine (Mayo test HMU24), Mayo Clinic Laboratories (catalog mirrored at testcatalog.org)
  3. Arsenic Toxicity: Clinical Assessment (Case Studies in Environmental Medicine), ATSDR (archived copy)
  4. Arsenic Toxicity: Biologic Fate (Case Studies in Environmental Medicine), ATSDR (archived copy)
  5. Recommendations for provoked challenge urine testing, Journal of Medical Toxicology (2013)
  6. 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.

Related markers