Arsenic may be measured in blood or urine to monitor excessive environmental or occupational exposure, confirm a diagnosis of poisoning in hospitalized victims or to assist in the forensic investigation in a case of fatal over dosage. Some analytical techniques are capable of distinguishing organic from inorganic forms of the element. Organic arsenic compounds tend to be eliminated in the urine in unchanged form, while inorganic forms are largely converted to organic arsenic compounds in the body prior to urinary excretion. The current biological exposure index for U.S. workers of 35 µg/L total urinary arsenic may easily be exceeded by a healthy person eating a seafood meal.

Tests are available to diagnose poisoning by measuring arsenic in blood, urine, hair, and fingernails. The urine test is the most reliable test for arsenic exposure within the last few days. Urine testing needs to be done within 24–48 hours for an accurate analysis of an acute exposure. Tests on hair and fingernails can measure exposure to high levels of arsenic over the past 6–12 months. These tests can determine if one has been exposed to above-average levels of arsenic. They cannot predict, however, whether the arsenic levels in the body will affect health. Chronic arsenic exposure can remain in the body systems for a longer period of time than a shorter term or more isolated exposure and can be detected in a longer time frame after the introduction of the arsenic, important in trying to determine the source of the exposure.

Hair is a potential bioindicator for arsenic exposure due to its ability to store trace elements from blood. Incorporated elements maintain their position during growth of hair. Thus for a temporal estimation of exposure, an assay of hair composition needs to be carried out with a single hair which is not possible with older techniques requiring homogenization and dissolution of several strands of hair. This type of biomonitoring has been achieved with newer microanalytical techniques like Synchrotron radiation based X ray fluorescence (SXRF) spectroscopy and Microparticle induced X ray emission (PIXE).The highly focused and intense beams study small spots on biological samples allowing analysis to micro level along with the chemical speciation. In a study, this method has been used to follow arsenic level before, during and after treatment with Arsenious oxide in patients with Acute Promyelocytic Leukemia.

The current reference range for acceptable blood lead concentrations in healthy persons without excessive exposure to environmental sources of lead is less than 5 µg/dL for children. It was less than 25 µg/dL for adults. Previous to 2012 the value for children was 10 (µg/dl). The current biological exposure index (a level that should not be exceeded) for lead-exposed workers in the U.S. is 30 µg/dL in a random blood specimen.

In 2015, US HHS/CDC/NIOSH designated 5 µg/dL (five micrograms per deciliter) of whole blood, in a venous blood sample, as the reference blood lead level for adults. An elevated BLL is defined as a BLL ≥5 µg/dL. This case definition is used by the ABLES program, the Council of State and Territorial Epidemiologists (CSTE), and CDC’s National Notifiable Diseases Surveillance System (NNDSS). Previously (i.e. from 2009 until November 2015), the case definition for an elevated BLL was a BLL ≥10 µg/dL. The U.S. national BLL geometric mean among adults was 1.2 μg/dL in 2009–2010.

Blood lead concentrations in poisoning victims have ranged from 30->80 µg/dL in children exposed to lead paint in older houses, 77–104 µg/dL in persons working with pottery glazes, 90–137 µg/dL in individuals consuming contaminated herbal medicines, 109–139 µg/dL in indoor shooting range instructors and as high as 330 µg/dL in those drinking fruit juices from glazed earthenware containers.

Old methods of detection involve colorimetric assays such as the Prussian Blue test, the pyridine-barbiturate assay and the taurine fluorescence-HPLC but like all colorimetric assays these can be prone to false positives. Lipid peroxidation, an artifact of heart attack produces dialdehydes that cross-react with the pyridine-barbiturate assay. Meanwhile, the taurine-fluorescence-HPLC assay used for cyanide detection is identical to the assay used to detect glutathione in spinal fluid. Recently, cyanide and thiocyanate assays have been run with mass spectrometry (LC/MS/MS), which are considered specific tests. Since cyanide has such a short half-life, the main metabolite, thiocyanate is typically measured to determine exposure.

People are continually exposed to metals in the environment. Medical tests can detect metals often, but this is to be expected and alone is not evidence that a person is poisoned. Metal screening tests should not be used unless there is reason to believe that a person has had excessive exposure to metals. People should seek medical testing for poisoning only if they are concerned for a particular reason, and physicians should consider a patient's history and physical examination before conducting tests to detect metals.

Decontamination of people exposed to hydrogen cyanide gas only requires removal of the outer clothing and the washing of their hair. Those exposed to liquids or powders generally require full decontamination.

Diagnosis of elemental or inorganic mercury poisoning involves determining the history of exposure, physical findings, and an elevated body burden of mercury. Although whole-blood mercury concentrations are typically less than 6 μg/L, diets rich in fish can result in blood mercury concentrations higher than 200 μg/L; it is not that useful to measure these levels for suspected cases of elemental or inorganic poisoning because of mercury's short half-life in the blood. If the exposure is chronic, urine levels can be obtained; 24-hour collections are more reliable than spot collections. It is difficult or impossible to interpret urine samples of patients undergoing chelation therapy, as the therapy itself increases mercury levels in the samples.

Diagnosis of organic mercury poisoning differs in that whole-blood or hair analysis is more reliable than urinary mercury levels.

Diagnosis includes determining the clinical signs and the medical history, with inquiry into possible routes of exposure. Clinical toxicologists, medical specialists in the area of poisoning, may be involved in diagnosis and treatment.

The main tool in diagnosing and assessing the severity of lead poisoning is laboratory analysis of the blood lead level (BLL).

Blood film examination may reveal basophilic stippling of red blood cells (dots in red blood cells visible through a microscope), as well as the changes normally associated with iron-deficiency anemia (microcytosis and hypochromasia). However, basophilic stippling is also seen in unrelated conditions, such as megaloblastic anemia caused by vitamin B12 (colbalamin) and folate deficiencies.

Exposure to lead also can be evaluated by measuring erythrocyte protoporphyrin (EP) in blood samples. EP is a part of red blood cells known to increase when the amount of lead in the blood is high, with a delay of a few weeks. Thus EP levels in conjunction with blood lead levels can suggest the time period of exposure; if blood lead levels are high but EP is still normal, this finding suggests exposure was recent. However, the EP level alone is not sensitive enough to identify elevated blood lead levels below about 35 μg/dL. Due to this higher threshold for detection and the fact that EP levels also increase in iron deficiency, use of this method for detecting lead exposure has decreased.

Blood lead levels are an indicator mainly of recent or current lead exposure, not of total body burden. Lead in bones can be measured noninvasively by X-ray fluorescence; this may be the best measure of cumulative exposure and total body burden. However this method is not widely available and is mainly used for research rather than routine diagnosis. Another radiographic sign of elevated lead levels is the presence of radiodense lines called lead lines at the metaphysis in the long bones of growing children, especially around the knees. These lead lines, caused by increased calcification due to disrupted metabolism in the growing bones, become wider as the duration of lead exposure increases. X-rays may also reveal lead-containing foreign materials such as paint chips in the gastrointestinal tract.

Fecal lead content that is measured over the course of a few days may also be an accurate way to estimate the overall amount of childhood lead intake. This form of measurement may serve as a useful way to see the extent of oral lead exposure from all the diet and environmental sources of lead.

Lead poisoning shares symptoms with other conditions and may be easily missed. Conditions that present similarly and must be ruled out in diagnosing lead poisoning include carpal tunnel syndrome, Guillain–Barré syndrome, renal colic, appendicitis, encephalitis in adults, and viral gastroenteritis in children. Other differential diagnoses in children include constipation, abdominal colic, iron deficiency, subdural hematoma, neoplasms of the central nervous system, emotional and behavior disorders, and intellectual disability.

Mercury thermometers and mercury light bulbs are not as common as they used to be, and the amount of mercury they contain is unlikely to be a health concern if handled carefully. However, broken items still require careful cleanup, as mercury can be hard to collect and it is easy to accidentally create a much larger exposure problem.

Thallium may be quantitated in blood or urine as a diagnostic tool in clinical poisoning situations or to aid in the medicolegal investigation of suspicious deaths. Normal background blood and urine concentrations in healthy persons are usually less than 1 μg/litre, but they are often in the 1–10 mg/litre range in survivors of acute intoxication.

Dimercaprol and dimercaptosuccinic acid are chelating agents that sequester the arsenic away from blood proteins and are used in treating acute arsenic poisoning. The most important side effect is hypertension. Dimercaprol is considerably more toxic than succimer.

DMSA monoesters, e.g. MiADMSA, are promising antidotes for arsenic poisoning. Calcium sodium edetate is also used.

The effect of mercury took some time – the latent period between ingestion and the first symptoms (typically paresthesia – numbness in the extremities) was between 16 and 38 days. Paresthesia was the predominant symptom in less serious cases. Worse cases included ataxia (typically loss of balance), blindness or reduced vision, and death resulting from central nervous system failure. Anywhere between 20 and 40 mg of mercury has been suggested as sufficient for paresthesia (between 0.5 and 0.8 mg/kg of body weight). On average, individuals affected consumed 20 kg or so of bread; the 73,000 tonnes provided would have been sufficient for over 3 million cases.

The hospital in Kirkuk received large numbers of patients with symptoms that doctors recognised from the 1960 outbreak. The first case of alkylmercury poisoning was admitted to hospital on 21 December. By 26 December, the hospital had issued a specific warning to the government. By January 1972, the government had started to strongly warn the populace about eating the grain, although dispatches did not mention the large numbers already ill. The Iraqi Army soon ordered disposal of the grain and eventually declared the death penalty for anyone found selling it. Farmers dumped their supplies wherever possible, and it soon got into the water supply (particularly the River Tigris), causing further problems. The government issued a news blackout and released little information about the outbreak.

The World Health Organization assisted the Iraqi government through the supply of drugs, analytical equipment and expertise. Many new treatments were tried, since existing methods for heavy metal poisoning were not particularly effective. Dimercaprol was administered to several patients, but caused rapid deterioration of their condition. It was ruled out as a treatment for this sort of poisoning following the outbreak. Polythiol resins, penicillamine and dimercaprol sulfonate all helped, but are believed to have been largely insignificant in overall recovery and outcomes. Dialysis was tested on a few patients late in the treatment period, but they showed no clinical improvement. The result of all treatments was varied, with some patients' blood mercury level being dramatically reduced, but a negligible effect in others. All patients received periods of treatment interspersed with lay periods; continuous treatment was suggested in future cases. Later treatment was less effective in reducing blood toxicity.

Most pesticide-related illnesses have signs and symptoms that are similar to common medical conditions, so a complete and detailed environmental and occupational history is essential for correctly diagnosing a pesticide poisoning. A few additional screening questions about the patient's work and home environment, in addition to a typical health questionnaire, can indicate whether there was a potential pesticide poisoning.

If one is regularly using carbamate and organophosphate pesticides, it is important to obtain a baseline cholinesterase test. Cholinesterase is an important enzyme of the nervous system, and these chemical groups kill pests and potentially injure or kill humans by inhibiting cholinesterase. If one has had a baseline test and later suspects a poisoning, one can identify the extent of the problem by comparison of the current cholinesterase level with the baseline level.

There are two main methods of removing both radioactive and stable isotopes of thallium from humans. First known was to use Prussian blue, which is a solid ion exchange material, which absorbs thallium. Up to 20 g per day of Prussian blue is fed by mouth to the person, and it passes through their digestive system and comes out in the stool. Hemodialysis and hemoperfusion are also used to remove thallium from the blood serum. At later stage of the treatment additional potassium is used to mobilize thallium from the tissue.

A number of measurements exist to assess exposure and early biological effects for organophosphate poisoning. Measurements of OP metabolites in both the blood and urine can be used to determine if a person has been exposed to organophosphates. Specifically in the blood, metabolites of cholinesterases, such as butyrylcholinesterase (BuChE) activity in plasma, neuropathy target esterase (NTE) in lymphocytes, and of acetylcholinesterase (AChE) activity in red blood cells. Due to both AChE and BuChE being the main targets of organophosphates, their measurement is widely used as an indication of an exposure to an OP. The main restriction on this type of diagnosis is that depending on the OP the degree to which either AChE or BuChE are inhibited differs; therefore, measure of metabolites in blood and urine do not specify for a certain OP. However, for fast initial screening, determining AChE and BuChE activity in the blood are the most widely used procedures for confirming a diagnosis of OP poisoning. The most widely used portable testing device is the Test-mate ChE field test, which can be used to determine levels of Red Blood Cells (RBC), AChE and plasma (pseudo) cholinesterase (PChE) in the blood in about four minutes. This test has been shown to be just as effective as a regular laboratory test and because of this, the portable ChE field test is frequently used by people who work with pesticides on a daily basis.

As many of the clinical signs and symptoms of ethylene glycol poisoning are nonspecific and occur in many poisonings the diagnosis is often difficult. It is most reliably diagnosed by the measurement of the blood ethylene glycol concentration. Ethylene glycol in biological fluids can be determined by gas chromatography. Many hospital laboratories do not have the ability to perform this blood test and in the absence of this test the diagnosis must be made based on the clinical presentation of the patient. In this situation a helpful test to diagnose poisoning is the measurement of the osmolal gap. The patients' serum osmolality is measured by freezing point depression and then compared with the predicted osmolality based on the patients' measured sodium, glucose, blood urea nitrogen, and any ethanol that may have been ingested. The presence of a large osmolal gap supports a diagnosis of ethylene glycol poisoning. However, a normal osmolar gap does not rule out ethylene glycol exposure because of wide individual variability.

The increased osmolal gap is caused by the ethylene glycol itself. As the metabolism of ethylene glycol progresses there will be less ethylene glycol and this will decrease the blood ethylene glycol concentration and the osmolal gap making this test less useful. Additionally, the presence of other alcohols such as ethanol, isopropanol, or methanol or conditions such as alcoholic or diabetic ketoacidosis, lactic acidosis, or kidney failure may also produce an elevated osmolal gap leading to a false diagnosis.

Other laboratory abnormalities may suggest poisoning, especially the presence of a metabolic acidosis, particularly if it is characterized by a large anion gap. Large anion gap acidosis is usually present during the initial stage of poisoning. However, acidosis has a large number of differential diagnosis, including poisoning from methanol, salicylates, iron, isoniazid, paracetamol, theophylline, or from conditions such as uremia or diabetic and alcoholic ketoacidosis. The diagnosis of ethylene glycol poisoning should be considered in any patient with a severe acidosis. Urine microscopy can reveal needle or envelope-shaped calcium oxalate crystals in the urine which can suggest poisoning; although these crystals may not be present until the late stages of poisoning. Finally, many commercial radiator antifreeze products have fluorescein added to enable radiator leaks to be detected using a Wood's lamp. Following ingestion of antifreeze products containing ethylene glycol and fluorescein, a Wood's lamp may reveal fluorescence of a patient’s mouth area, clothing, vomitus, or urine which can help to diagnose poisoning.

Chelation therapy is a medical procedure that involves the administration of chelating agents to remove heavy metals from the body. Chelating agents are molecules that have multiple electron-donating groups, which can form stable coordination complexes with metal ions. Complexation prevents the metal ions from reacting with molecules in the body, and enable them to be dissolved in blood and eliminated in urine. It should only be used in people who have a diagnosis of metal intoxication. That diagnosis should be validated with tests done in appropriate biological samples.

Chelation therapy is administered under very careful medical supervision due to various inherent risks. When the therapy is administered properly, the chelation drugs have significant side effects. Chelation administered inappropriately can cause neurodevelopmental toxicity, increase risk of developing cancer, and cause death; chelation also removes essential metal elements and requires measures to prevent their loss.

6,530 patients were admitted to hospitals with poisoning, and 459 deaths reported. Cases reached a peak of hundreds per day in January, and had largely subsided by the beginning of March. The last admittance was on 27 March; admissions represented every age and gender stratum, although those under the age of ten represented a third of admitted cases. This number is "certainly an underestimate", because of the availability of hospital treatment, hospital overcrowding and lack of faith in treatment. In the most severely affected areas, prevalence was 28% and mortality was 21% of the cases. Some Iraqi doctors believe both the number of cases and fatalities are at least ten times too low, with perhaps 100,000 cases of brain damage. One suggested reason for the vast discrepancy between reported and estimated numbers of deaths is the Iraqi custom, common to large parts of the Middle East, for a person to die at home when possible. Home deaths would not have been recorded.

A large number of patients with minor symptoms recovered completely; those with more serious symptoms improved. This was in contrast to expected outcomes, largely based on analysis of Minamata disease in Japan. In boys with mercury levels below clinical poisoning, a reduction in school performance was noted, although this correlation could not be confirmed. In infants, the mercury poisoning caused central nervous system damage. Relatively low doses caused slower development in children, and abnormal reflexes. Different treatments for mercury poisoning have since been developed, and "quiet baby syndrome", characterised by a baby who never cries, is now a recognised symptom of methylmercury-induced brain damage. Ongoing recommendations of the food regulation authorities have focused on consumption by pregnant women and infant children, noting the particular susceptibility of fetuses and infants to methylmercury poisoning. Data from Iraq have confirmed that methylmercury can pass to a child "in utero", and mercury levels were equal to or higher in the newborn child than in the mother.

In 1974, a joint Food and Agriculture Organization (FAO) and World Health Organisation (WHO) meeting made several recommendations to prevent a similar outbreak. These included stressing the importance of labelling bags in the local language and with locally understood warning symbols. The possibility of an additive creating a strong bitter taste was studied. The meeting urged governments to strictly regulate methyl- and ethylmercury use in their respective countries, including limiting use to where no other reasonable alternative was available. It also recommended the involvement of the FAO and WHO in assisting national governments in regulation and enforcement, and the setting up of national poison control centres. Over 9–13 November, a Conference on Intoxication due to Alkylmercury-Treated Seed was held in Baghdad. It supported the recommendations of the FAO/WHO report and further suggested that local and national media should publicise outbreaks, including size and symptoms; it considered the distribution of this information crucial. It also laid out a general plan as to the collection of relevant information from the field and potential analysis for further investigation. It called on national governments to make use of WHO involvement whenever feasible, and absolved world governments in clear terms, saying that "No country should ever feel that any blame will attach to it for allowing an outbreak to occur".

Iraq now has the highest incidence of Parkinson's in the world. Parkinson's symptoms are very similar to mercury poisoning symptoms. Mercury that enters the brain has a half-life of 27.5 years and chelators are not able to remove it.

Accidental poisonings can be avoided by proper labeling and storage of containers. When handling or applying pesticides, exposure can be significantly reduced by protecting certain parts of the body where the skin shows increased absorption, such as the scrotal region, underarms, face, scalp, and hands. Safety protocols to reduce exposure include the use of personal protective equipment, washing hands and exposed skin during as well as after work, changing clothes between work shifts, and having first aid trainings and protocols in place for workers.

Personal protective equipment for preventing pesticide exposure includes the use of a respirator, goggles, and protective clothing, which have all have been shown to reduce risk of developing pesticide-induced diseases when handling pesticides. A study found the risk of acute pesticide poisoning was reduced by 55% in farmers who adopted extra personal protective measures and were educated about both protective equiment and pesticide exposure risk. Exposure can be significantly reduced when handling or applying pesticides by protecting certain parts of the body where the skin shows increased absorption, such as the scrotal region, underarms, face, scalp, and hands. Using chemical-resistant gloves has been shown to reduce contamination by 33–86%.

In Northern Australia, where ciguatera is a common problem, two different folk science methods are widely believed to detect whether fish harbor significant ciguatoxin. The first method is that flies are supposed not to land on contaminated fish. The second is that cats will either refuse to eat or vomit/display symptoms after eating contaminated fish. A third, less common testing method involves putting a silver coin under the scales of the suspect fish. If the coin turns black, according to the theory, it is contaminated.

On Grand Cayman and other islands the locals will test barracuda by placing a piece of the fish on the ground and allowing ants to crawl on it. If the ants do not avoid the flesh and will eat it, then the fish is deemed safe.

In Dominican Republic, another common belief is that during months whose names do not include the letter "R" (May through August), it is not recommended to eat certain kinds of fish, because they are more likely to be infected by the ciguatera toxin.

The validity of many of these tests has been scientifically rejected.

Antifreeze products for automotive use containing propylene glycol in place of ethylene glycol are available, and are generally considered safer to use, as it possesses an unpleasant taste in contrast to the perceived "sweet" taste of toxic ethylene glycol-based coolants, and only produces lactic acid in an animal's body, as their muscles do when exercised.

When using antifreeze products containing ethylene glycol, recommended safety measures include:

- Cleaning up any spill immediately and thoroughly. Spills may be cleaned by sprinkling cat litter, sand or other absorbent material directly on the spill. Once fully absorbed, while wearing protective gloves, the material may be scooped into a plastic bag, sealed and disposed. The spill area may be scrubbed with a stiff brush and warm, soapy water. The soapy water is not recommended to be drained in a storm drain.

- Checking vehicles regularly for leaks.

- Storing antifreeze in clearly marked original sealed containers, in areas that are inaccessible to pets or small children.

- Keeping pets and small children away from the area when draining the car radiator.

- Disposing of used antifreeze only by taking to a service station.

- If antifreeze is placed in toilets, ensuring the lid is down and the door closed.

Various Caribbean folk and ritualistic treatments originated in Cuba and nearby islands. The most common old-time remedy involves bed rest subsequent to a guanabana juice enema. Other folk treatments range from directly porting and bleeding the gastrointestinal tract to "cleansing" the diseased with a dove during a Santería ritual. In Puerto Rico, natives drink a tea made from mangrove buttons, purportedly high in B vitamins, to flush the toxic symptoms from the system. There has never been a funded study of these treatments.

An account of ciguatera poisoning from a linguistics researcher living on Malakula island, Vanuatu, indicates the local treatment: "We had to go with what local people told us: avoid salt and any seafood. Eat sugary foods. And they gave us a tea made from the roots of ferns growing on tree trunks. I don't know if any of that helped, but after a few weeks, the symptoms faded away."

Senescent leaves of "Heliotropium foertherianum" (Boraginaceae), also known as octopus bush, a plant used in many Pacific islands as a traditional medicine to treat ciguatera fish poisoning, contain rosmarinic acid and derivatives, which are known for their antiviral, antibacterial, antioxidant and anti-inflammatory properties. Rosmarinic acid may remove the ciguatoxins from their sites of action, as well as being an anti-inflammatory.

Some medications that can be used for erethism are Traid and Ritalin. Methylphenidate (Ritalin) is a stimulant drug approved for therapy of attention-deficit hyperactivity disorder, postural orthostatic tachycardia syndrome and narcolepsy. It may also be prescribed for off-label use in treatment-resistant cases of lethargy, depression (mood), or neural insult.

One treatment of mercury poisoning was to admit fresh air to the patient by having him go outside daily as much as possible. Stimulants such as ammonia have also been documented to help restore pulse to a normal rhythm. For a more comprehensive reading of treatment, see Mercury poisoning, 'Treatment' section.

The management of AAlPP remains purely supportive because no specific antidote exists. Mortality rates approach 60%. Correction of metabolic acidosis is a cornerstone of treatment. The role of magnesium sulfate as a potential therapy in AlP poisoning may decrease the likelihood of a fatal outcome, and has been described in many studies. After ingestion, removal of unabsorbed poison from the gut ("gut decontamination"), especially if administered within 1–2 hours, can be effective. Potassium permanganate (1:10,000) gastric lavage can decompose the toxin. All patients of severe AlP poisoning require continuous invasive hemodynamic monitoring and early resuscitation with fluid and vasoactive agents.

In humans, heavy metal poisoning is generally treated by the administration of chelating agents.

These are chemical compounds, such as (calcium disodium ethylenediaminetetraacetate) that convert heavy metals to chemically inert forms that can be excreted without further interaction with the body. Chelates are not without side effects and can also remove beneficial metals from the body. Vitamin and mineral supplements are sometimes co-administered for this reason.

Soils contaminated by heavy metals can be remediated by one or more of the following technologies: isolation; immobilization; toxicity reduction; physical separation; or extraction. "Isolation" involves the use of caps, membranes or below-ground barriers in an attempt to quarantine the contaminated soil. "Immobilization" aims to alter the properties of the soil so as to hinder the mobility of the heavy contaminants. "Toxicity reduction" attempts to oxidise or reduce the toxic heavy metal ions, via chemical or biological means into less toxic or mobile forms. "Physical separation" involves the removal of the contaminated soil and the separation of the metal contaminants by mechanical means. "Extraction" is an on or off-site process that uses chemicals, high-temperature volatization, or electrolysis to extract contaminants from soils. The process or processes used will vary according to contaminant and the characteristics of the site.

The 1858 Bradford sweets poisoning was the arsenic poisoning of more than 200 people in Bradford, England, when sweets accidentally made with arsenic were sold from a market stall. Twenty-one victims died as a result. The event contributed to the passage of the Pharmacy Act 1868 in the United Kingdom and legislation regulating the adulteration of foodstuffs.