Why must patients avoid seafood before the test?

Fish, shellfish, and seaweed contain non-toxic organic arsenicals that markedly elevate total arsenic in blood and urine but are not clinically significant. A 48–72-hour seafood-free period ensures the measured arsenic reflects inorganic exposure.

Can a normal blood arsenic rule out arsenic poisoning?

No. Because blood arsenic has a half-life of hours to days, a normal result drawn more than 48 hours post-exposure does not exclude clinically significant poisoning. For chronic or past exposure, urine testing with speciation is required.

What are the symptoms of acute arsenic poisoning?

Acute inorganic arsenic poisoning presents with nausea, vomiting, abdominal pain, watery or bloody diarrhoea, hypotension, encephalopathy, peripheral neuropathy, and characteristic skin changes (hyperkeratosis, hyperpigmentation). Blood arsenic should be drawn as soon as possible after symptom onset.

What collection tubes are required for blood arsenic?

Trace-element-free tubes (royal blue top or equivalent specified by Quest) are mandatory to prevent contamination. Standard evacuated tubes can introduce spurious arsenic, invalidating the result.

Is arsenic speciation available on blood?

Speciation — distinguishing inorganic arsenic from organic forms — is performed routinely on urine and less commonly on blood. Total blood arsenic does not differentiate toxic from non-toxic species, so dietary history and clinical context are critical, and urine speciation is preferred.

How long does the blood arsenic test take?

Results are typically available within 3–7 business days from specimen receipt at Quest's reference laboratory, though turnaround may extend if confirmation or speciation is requested.

Who is at risk for occupational arsenic exposure?

Workers in smelting, wood preservation (historical chromated copper arsenate), pesticide and herbicide manufacture, semiconductor fabrication, and glass production face occupational arsenic exposure. Blood testing confirms recent exposure; urine surveillance monitors chronic risk.

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Arsenic, Blood

Q: What is the difference between blood and urine arsenic testing?

Blood arsenic reflects exposure within the preceding 24–48 hours because arsenic clears rapidly from blood. Urine arsenic, especially 24-hour collection with speciation, captures recent days to weeks and distinguishes toxic inorganic arsenic from benign dietary organics, making it the preferred matrix for chronic or occupational surveillance.

Q: What does an elevated blood arsenic indicate?

An elevated level above 10–15 µg/L suggests recent inorganic arsenic exposure if seafood is excluded. Values above 50–100 µg/L raise strong suspicion of acute poisoning and warrant chelation, supportive care, and source removal. Clinical correlation and urine speciation are essential.

Blood arsenic quantifies total elemental arsenic in whole blood, documenting acute or very recent inorganic arsenic exposure. Its short half-life makes it timing-critical; levels fall within days as arsenic redistributes and is excreted in urine. Seafood elevates total arsenic markedly, so dietary abstinence and speciation are essential.

Biomarkers

Blood (whole blood)

Sample

3–7 business days

Turnaround

Fasting

What is the Blood Arsenic test?

The Blood Arsenic test quantifies total elemental arsenic in whole blood and is used to document acute or very recent exposure to inorganic arsenic, the toxic form implicated in acute poisoning and long-term carcinogenesis. Practitioners order it when a patient presents with symptoms consistent with arsenic toxicity — nausea, vomiting, abdominal pain, peripheral neuropathy, or skin changes — or when occupational or environmental exposure is suspected and confirmation is needed within hours to days of the event. Blood is not the matrix of choice for chronic surveillance or retrospective diagnosis. Arsenic clears from blood within a couple of days, redistributing into tissues and excreting via urine, so a normal blood level does not rule out past exposure or chronic low-level poisoning. For those scenarios, 24-hour urine arsenic with speciation of inorganic and methylated metabolites is the reference standard. Blood arsenic serves a narrow window: documenting that arsenic is present in the circulation at the moment of the draw, which is most useful in acute toxicity and outbreak investigations.

What does the Blood Arsenic test measure?

As(Arsenic, Blood)

Range: <7 µg/L in unexposed individuals; timing-dependent and influenced by recent seafood.Optimal: Whole-blood arsenic <3–5 µg/L in individuals with no occupational exposure and no recent seafood intake; however, clinical decisions are based on the speciated inorganic fraction when possible and the exposure context.µg/L / µg/dL

Arsenic exists in multiple chemical forms with different toxicological profiles. Inorganic arsenic (arsenite and arsenate) and their methylated metabolites are toxic and carcinogenic; organic arsenoarsenicals from seafood (arsenobetaine, arsenocholine, arsenosugars) are essentially non-toxic and rapidly cleared in urine. Whole-blood arsenic reflects recent absorption — inorganic arsenic is distributed to tissues within hours and methylated hepatically to monomethylarsonic acid and dimethylarsinic acid, with a blood half-life measured in hours to a few days. Blood arsenic is therefore a snapshot of very recent exposure, and its measurement includes all chemical species unless speciation is requested.

Blood arsenic is used to confirm acute or very recent inorganic arsenic exposure in symptomatic patients or shortly after a known exposure event. Because arsenic clears rapidly from blood into tissue and urine, an elevated level documents recent intake but a normal value does not exclude past exposure or chronic low-level poisoning. For chronic or occupational surveillance, urine arsenic with speciation is the preferred matrix. Seafood consumption within the preceding 48 hours can elevate total blood arsenic substantially, so timing and dietary history are critical to interpretation.

Why is the Blood Arsenic test ordered?

Acute arsenic poisoning suspected on clinical grounds — gastrointestinal distress, hypotension, encephalopathy, or characteristic skin lesions — within 24–48 hours of exposure
Known or suspected occupational exposure in smelting, wood preservation, pesticide manufacture, or semiconductor industries, when recent exposure confirmation is required
Environmental exposure incidents (contaminated drinking water or food) where blood sampling occurs shortly after the event
Medico-legal or forensic investigation of poisoning, with the sample drawn as close to the exposure as possible
Paediatric ingestion or accidental exposure to arsenic-containing compounds, to guide chelation therapy decisions
Outbreak investigation by public-health authorities, to confirm exposure in a cohort and correlate with clinical findings

Sample collection and turnaround

Sample type

Blood (whole blood)

Fasting required

Collection method

Venipuncture at patient service centre

Turnaround

3–7 business days

Collection notes

Phlebotomy via Quest; use certified trace-element-free collection tubes (royal blue top or equivalent specified by the laboratory) to prevent contamination. Patients must abstain from seafood and seaweed for 48–72 hours before collection to avoid false elevation from dietary organoarsenicals. Collect as soon as possible after suspected acute exposure, ideally within 24–48 hours.

Specimen requirements

Minimum 3–5 mL whole blood in a trace-element-free tube (typically sodium heparin or EDTA as specified by Quest). Do not use standard evacuated tubes. Reject haemolysed specimens. Refrigerate and transport cold; check the laboratory manual for specific shipping requirements.

What can affect Blood Arsenic results?

elevatesRecent seafood consumption

Fish, shellfish, and seaweed contain organic arsenicals (arsenobetaine, arsenocholine) that are non-toxic but raise total blood and urine arsenic markedly; patients should abstain from seafood for 48–72 hours before testing, and speciation is essential if dietary history is unclear.

reducesTime since exposure

Blood arsenic has a half-life of hours to a few days; levels fall rapidly as arsenic distributes into tissues and is excreted in urine, so sampling more than 48 hours post-exposure may miss clinically significant poisoning.

elevatesSpecimen contamination

Trace-element contamination from collection tubes, needles, or processing equipment can spuriously elevate results; use certified trace-element-free or royal-blue-top tubes and follow the laboratory's specimen-collection protocol rigorously.

variableHaemolysis

Arsenic is present in red cells, so haemolysed specimens may yield falsely elevated whole-blood values; grossly haemolysed samples should be rejected.

elevatesOccupational or medicinal exposure to organoarsenicals

Historical medicinal arsenicals (no longer in routine use) and certain veterinary feed additives raise total arsenic; clinical and occupational history guides whether the measured arsenic is inorganic or organic.

elevatesRenal impairment

Reduced urinary clearance prolongs blood and tissue arsenic, though urine remains the preferred matrix for chronic assessment; interpret blood levels in the context of renal function.

What do Blood Arsenic results mean?

Elevated

Blood arsenic >10–15 µg/L suggests recent inorganic arsenic exposure if seafood is excluded; values >50–100 µg/L raise strong suspicion of acute poisoning and warrant chelation consideration, supportive care, and removal from the source. Correlate with clinical findings, obtain urine speciation, and reassess serially as blood levels fall. Even moderately elevated levels are clinically significant in the appropriate exposure context.

Normal

Blood arsenic below the reference threshold (<7 µg/L) in the absence of recent seafood intake is consistent with no recent inorganic exposure. A normal result drawn more than 48 hours after a suspected exposure does not rule out clinically significant poisoning — urine arsenic and speciation remain necessary if clinical suspicion persists.

Reduced

Low or undetectable blood arsenic is normal in unexposed individuals and does not require further action. It does not exclude past exposure or chronic low-level poisoning, for which urine testing is appropriate.

Note: Blood arsenic is timing-critical and seafood-sensitive; a careful dietary and exposure history is mandatory. Total arsenic does not distinguish toxic inorganic forms from benign organic arsenicals — speciation (available for urine, less commonly performed on blood) is the gold standard when the source is uncertain. For chronic exposure or occupational surveillance, 24-hour urine arsenic with speciation is preferred over blood.

Frequently asked questions

Blood arsenic reflects exposure within the preceding 24–48 hours because arsenic clears rapidly from blood. Urine arsenic, especially 24-hour collection with speciation, captures recent days to weeks and distinguishes toxic inorganic arsenic from benign dietary organics, making it the preferred matrix for chronic or occupational surveillance.

How to access the Blood Arsenic test

The Blood Arsenic reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.

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About this page

Published: October 7, 2026

Last reviewed: October 7, 2026

References:

Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for arsenic. (2007)
Klaassen CD, Watkins JB, eds. Casarett and Doull's Essentials of Toxicology, 3rd ed. (Chapter on arsenic). (2015)
World Health Organization. Arsenic in drinking-water: background document for development of WHO guidelines for drinking-water quality. (2011)
Hughes MF, et al. Arsenic exposure and toxicology: a historical perspective. Toxicol Sci. (2011)
National Research Council. Arsenic in Drinking Water: 2001 Update. National Academies Press. (2001)

This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.