Arsenic Test · Blood

If you drink well water, eat a lot of rice, or live in a region with naturally arsenic-rich soil, you could be absorbing a known carcinogen every day without ever feeling sick. Arsenic does not announce itself with obvious symptoms. It builds up quietly, and by the time skin changes, nerve tingling, or a cancer diagnosis appears, the exposure may have been going on for years or decades.

A blood arsenic test tells you how much of this toxic element is circulating in your body right now. Unlike most biomarkers on this site, arsenic is not something your body makes. Lower is always better, and there is no known safe threshold. Your result reflects what you have been exposed to and how well your body clears it.

What Arsenic Is and How It Gets Into Your Body

Arsenic is a naturally occurring element found in rock and soil. It exists in two broad forms: inorganic arsenic, which is highly toxic, and organic arsenic, which is found mostly in seafood and is largely harmless. Inorganic arsenic enters drinking water when groundwater dissolves arsenic-containing minerals. It also contaminates rice (which absorbs it from flooded paddies), some cereals, and can be released by mining, smelting, and industrial processes.

Once inorganic arsenic enters your body, your liver converts it through a process called methylation, which adds small chemical groups to the arsenic molecule so your kidneys can flush it out. The efficiency of this conversion varies from person to person and depends heavily on your folate and B vitamin status, your genetics, and your sex. Women and younger people tend to methylate arsenic more efficiently than men and older adults.

Cancer Risk

Inorganic arsenic is classified as a Group 1 carcinogen, the highest category of certainty. In the Strong Heart Study, a prospective study of 3,932 American Indian adults followed for up to 19 years, even low to moderate arsenic exposure was linked to specific cancers. Comparing the 80th to the 20th percentile of urinary arsenic, the risk of dying from lung cancer was about 56% higher, prostate cancer risk was about 3.3 times higher, and pancreatic cancer risk was roughly 2.5 times higher.

A meta-analysis of skin cancer studies including over 48,000 participants found that arsenic exposure was linked to about 50% higher odds of skin cancer overall, with similar increases for melanoma, squamous cell carcinoma, and basal cell carcinoma. These risks appeared even at water concentrations below 10 micrograms per liter, the current World Health Organization guideline.

Heart Disease and Stroke

A large meta-analysis pooling 37 studies with over 348,000 participants found that people in the top third of arsenic exposure had about 30% higher risk of cardiovascular disease and 23% higher risk of coronary heart disease compared to those in the bottom third. The relationship followed a straight line: more arsenic, more risk, with no safe floor identified.

Smoking makes the danger worse. In the Bangladeshi cohort, the combination of arsenic exposure and cigarette smoking more than doubled heart disease mortality beyond what either risk factor would predict alone.

Diabetes and Metabolic Disease

The relationship between arsenic and type 2 diabetes is real but complicated. A meta-analysis of 32 ingestion studies found that people in the highest arsenic exposure groups had about 57% higher risk of diabetes compared to the lowest groups. A combined analysis of the Strong Heart Family Study and the Multi-Ethnic Study of Atherosclerosis (MESA), following over 7,500 participants, found that each doubling of community water arsenic was linked to a 10% increase in diabetes incidence, even at levels below 10 micrograms per liter.

An Italian cohort study of over 165,000 residents exposed to low to moderate arsenic through drinking water found that women in the highest exposure group had about 2.5 times the risk of dying from diabetes compared to those in the lowest group. The twist is that how your body processes arsenic matters too: in the Strong Heart Study, people who converted more arsenic into a specific breakdown product called DMA (dimethylarsinate) had higher diabetes risk, while those who produced more of a different product called MMA (monomethylarsonate) had lower diabetes risk but higher cancer risk.

Kidney and Neurological Damage

In a large German outpatient cohort of nearly 59,000 people, whole blood arsenic correlated inversely with kidney filtration rate (eGFR), meaning higher arsenic was associated with worse kidney function, even in people without known kidney disease or occupational exposure. This relationship held after adjusting for age, sex, inflammation, and blood sugar, and was strongest in younger adults.

Chronic arsenic exposure also damages the nervous system. In children, systematic reviews have linked arsenic exposure to lower IQ scores, slower processing speed, and impaired memory and language skills. In adults, peripheral neuropathy (numbness and tingling in the hands and feet) is one of the classic signs of chronic arsenic toxicity.

Reference Ranges

There is no universally standardized clinical reference range for blood arsenic in the way there is for cholesterol or blood sugar. The values below are drawn from population studies, not clinical guidelines, and serve as orientation rather than firm clinical targets. Your lab may report results in different units. The consistent theme across the research is that lower is better and no clearly safe threshold has been identified.

In a German cohort of nearly 59,000 outpatients, the median whole blood arsenic was 0.8 µg/L. In a Chinese study of over 2,300 older adults, the median was 1.41 µg/L. A South African control village with no known arsenic contamination had a median of 0.6 µg/L. Compare your results within the same lab over time for the most meaningful trend.

When Results Can Be Misleading

The biggest confounder for any arsenic test is recent seafood intake. Fish, shellfish, and seaweed contain large amounts of organic arsenic (mostly arsenobetaine), which is nontoxic but shows up on many standard arsenic assays. If you ate seafood in the 2 to 3 days before your blood draw, your total arsenic reading could be dramatically inflated without reflecting any dangerous inorganic arsenic exposure. Ask your lab whether they report total arsenic or speciated arsenic, and avoid seafood for at least 48 to 72 hours before testing.

• Seafood intake: Can raise total blood arsenic several-fold through harmless organic arsenic species. This is the most common cause of a misleading high result.
• Kidney function: Arsenic is cleared through the kidneys. Reduced kidney filtration can slow clearance and make blood arsenic appear higher than it would be in someone with normal kidney function.
• Hydration and sample timing: Dehydration can concentrate the blood sample. There is no strong circadian rhythm for arsenic, but consistency in timing across tests improves comparability.
• Genetics: Variants in the AS3MT gene (which controls arsenic methylation) can explain up to 50 to 63% of differences in how people process arsenic, meaning two people with the same exposure can have very different blood levels.

Tracking Your Trend

Arsenic has a biological half-life of about 4 days in the body, meaning blood levels reflect primarily recent exposure over the past week or so. A single reading tells you what is happening right now, but a series of readings over months tells you whether your exposure is truly chronic or was just a one-time event.

In a longitudinal study tracking arsenic levels over 2 years, the consistency of repeat measurements within the same person was moderate, with intraclass correlation coefficients (a measure of how stable your readings are over time, where 1.0 means perfectly stable) around 0.35 to 0.49 for urinary arsenic species. This means a single test gives you a reasonable estimate, but confirming a high result with a second test under the same conditions (same fasting state, same avoidance of seafood) makes the reading much more reliable.

If you are testing because you suspect an exposure source, get a baseline test now. If you then change your water source, switch to a filter, or alter your diet, retest in 2 to 4 weeks to see whether your level dropped. For ongoing monitoring in a known exposure area, testing every 6 to 12 months provides a useful trend. If you are testing as a one-time screen with no known exposure, a single low result is reassuring.

What to Do With an Abnormal Result

If your blood arsenic comes back elevated, the first step is to identify and eliminate the source. Test your drinking water if you use a private well. Review your diet for high-rice intake or frequent seafood consumption. Retest your blood in 3 to 4 weeks after eliminating the suspected source to confirm whether levels are falling.

If levels remain high after removing obvious sources, consider ordering a speciated urine arsenic test, which separates inorganic arsenic from harmless organic forms and can confirm whether you are truly exposed to the toxic species. A complete metabolic panel, kidney function tests (cystatin C or eGFR), and liver enzymes (ALT, AST) are worth running alongside, since arsenic damages both organs. For anyone with a confirmed chronic exposure, a conversation with a toxicologist or environmental medicine specialist is the appropriate next step.

Folate status is directly relevant. If your folate is low, your body cannot methylate and clear arsenic efficiently. Checking your vitamin B9 level (folate) and supplementing if deficient is one of the few evidence-based interventions that genuinely improves arsenic clearance.