Substance intoxication is a type of substance use disorder which is potentially maladaptive and impairing, but reversible, and associated with recent use.

If the symptoms are severe, the term "substance intoxication delirium" may be used.

Generic slang terms include: getting high or being stoned or blazed (all usually in reference to cannabis), with many more specific slang terms for each particular type of intoxicant. Alcohol intoxication is even graded in intensity, from buzzed, to tipsy, all the way up to hammered, smashed, wasted, destroyed, and a number of other similar terms.

Examples (and ICD-10 code) include:

- F10.0 alcohol intoxication

- F11.0 opioid intoxication

- F12.0 cannabinoid intoxication

- F13.0 sedative and hypnotic intoxication (see benzodiazepine overdose and barbiturate overdose)

- F14.0 cocaine intoxication

- F15.0 caffeine intoxication

- F16.0 hallucinogen intoxication (See for example Lysergic acid diethylamide effects)

- F17.0 tobacco intoxication

The term contact high is sometimes used to describe intoxication without direct administration, either by second-hand smoke as with cannabis, or by placebo in the presence of others who are high.

The main symptoms of delirium tremens are nightmares, agitation, global confusion, disorientation, visual and auditory hallucinations, tactile hallucinations, fever, high blood pressure, heavy sweating, and other signs of autonomic hyperactivity (fast heart rate and high blood pressure). These symptoms may appear suddenly, but typically develop two to three days after the stopping of heavy drinking, being worst on the fourth or fifth day. Also, these "symptoms are characteristically worse at night". In general, DT is considered the most severe manifestation of alcohol withdrawal and occurs 3–10 days following the last drink. Other common symptoms include intense perceptual disturbance such as visions of insects, snakes, or rats. These may be hallucinations, or illusions related to the environment, e.g., patterns on the wallpaper or in the peripheral vision that the patient falsely perceives as a resemblance to the morphology of an insect, and are also associated with tactile hallucinations such as sensations of something crawling on the subject—a phenomenon known as formication. Delirium tremens usually includes extremely intense feelings of "impending doom". Severe anxiety and feelings of imminent death are common DT symptoms.

DT can sometimes be associated with severe, uncontrollable tremors of the extremities and secondary symptoms such as anxiety, panic attacks and paranoia. Confusion is often noticeable to onlookers as those with DT will have trouble forming simple sentences or making basic logical calculations.

DT should be distinguished from alcoholic hallucinosis, the latter of which occurs in approximately 20% of hospitalized alcoholics and does not carry a significant mortality. In contrast, DT occurs in 5–10% of alcoholics and carries up to 15% mortality with treatment and up to 35% mortality without treatment. DT is characterized by the presence of altered sensorium; that is, a complete hallucination without any recognition of the real world. DT has extreme autonomic hyperactivity (high pulse, blood pressure, and rate of breathing), and 35-60% of patients have a fever. Some patients experience seizures.

Combined drug intoxication (CDI), also known as multiple drug intake (MDI) or lethal polydrug/polypharmacy intoxication, is an unnatural cause of human death. CDI is often confused with drug overdose, but it is a completely different phenomenon. It is distinct in that it is due to the simultaneous use of multiple drugs, whether the drugs are prescription, over-the-counter, recreational, or some other combination. Alcohol can exacerbate the symptoms and may directly contribute to increased severity of symptoms. The reasons for toxicity vary depending on the mixture of drugs. Usually, most victims die after using two or more drugs in combination that suppress breathing, and the low blood oxygen level causes brain death.

The CDI/MDI phenomenon seems to be becoming more common in recent years. In December 2007, according to Dr. John Mendelson, a pharmacologist at the California Pacific Medical Center Research Institute, deaths by combined drug intoxication were relatively "rare" ("one in several million"), though they appeared then to be "on the rise". In July 2008, the Associated Press and CNN reported on a medical study showing that over two decades, from 1983 to 2004, such deaths have soared. It has also become a prevalent risk for older patients.

Different concentrations of alcohol in the human body have different effects on the subject.

The following lists the common effects of alcohol on the body, depending on the blood alcohol concentration (BAC). However, tolerance varies considerably between individuals, as does individual response to a given dosage; the effects of alcohol differ widely between people. Hence, BAC percentages are just estimates used for illustrative purposes.

- Euphoria (BAC = 0.03% to 0.12%):

- Overall improvement in mood and possible euphoria

- Increased self-confidence

- Increased sociability

- Decreased anxiety

- Shortened attention span

- Flushed appearance

- Impaired judgment

- Impaired fine muscle coordination

- Lethargy (BAC = 0.09% to 0.25%)

- Sedation

- Impaired memory and comprehension

- Delayed reactions

- Ataxia; balance difficulty; unbalanced walk

- Blurred vision; other senses may be impaired

- Confusion (BAC = 0.18% to 0.30%)

- Profound confusion

- Impaired senses

- Analgesia

- Increased ataxia; impaired speech; staggering

- Dizziness often associated with nausea ("the spins")

- Vomiting (emesis)

- Stupor (BAC = 0.25% to 0.40%)

- Severe ataxia

- Lapses in and out of consciousness

- Unconsciousness

- Anterograde amnesia

- Vomiting (death may occur due to inhalation of vomit (pulmonary aspiration) while unconscious)

- Respiratory depression (potentially life-threatening)

- Decreased heart rate (usually results in coldness and/or numbness of the limbs)

- Urinary incontinence

- Coma (BAC = 0.35% to 0.80%)

- Unconsciousness (coma)

- Depressed reflexes (i.e., pupils do not respond appropriately to changes in light)

- Marked and life-threatening respiratory depression

- Markedly decreased heart rate

- Most deaths from alcohol poisoning are caused by dosage levels in this range.

Both alcoholic hallucinosis and DTs have been thought of as different manifestations of the same physiological process in the body during alcohol withdrawal. Alcoholic hallucinosis is a much less serious diagnosis than delirium tremens. Delirium tremens (DTs) do not appear suddenly, unlike alcoholic hallucinosis. DTs also take approximately 48 to 72 hours to appear after the heavy drinking stops. A tremor develops in the hands and can also affect the head and body. A common symptom of delirium tremens is that people become severely uncoordinated. The biggest difference between alcoholic hallucinosis and delirium tremens is that alcoholic hallucinosis have a much better prognosis than DTs. Moreover, delirium tremens can be fatal when untreated.

The short-term effects of alcohol (also known formally as ethanol) consumption–due to drinking beer, wine, distilled spirits or other alcoholic beverages–range from a decrease in anxiety and motor skills and euphoria at lower doses to intoxication (drunkenness), stupor, unconsciousness, anterograde amnesia (memory "blackouts"), and central nervous system depression at higher doses. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every cell in the body.

The concentration of alcohol in blood is measured via blood alcohol content (BAC). The amount and circumstances of consumption play a large part in determining the extent of intoxication; for example, eating a heavy meal before alcohol consumption causes alcohol to absorb more slowly. The amount of alcohol consumed largely determines the extent of hangovers, although hydration also plays a role. After excessive drinking, stupor and unconsciousness can occur. Extreme levels of consumption can lead to alcohol poisoning and death (a concentration in the blood stream of 0.40% will kill half of those affected). Alcohol may also cause death indirectly, by asphyxiation from vomit.

Alcohol can greatly exacerbate sleep problems. During abstinence, residual disruptions in sleep regularity and sleep patterns are the greatest predictors of relapse.

People who engage in polypharmacy and other hypochondriac behaviors are at an elevated risk of death from CDI. Elderly people are at the highest risk of CDI, because of having many age-related health problems requiring many medications combined with age-impaired judgment, leading to confusion in taking medications.

Acute alcohol poisoning is a related medical term used to indicate a dangerously high concentration of alcohol in the blood, high enough to induce coma, respiratory depression, or even death. It is considered a medical emergency. The term is mostly used by healthcare providers. Toxicologists use the term "alcohol intoxication" to discriminate between alcohol and other toxins.

The signs and symptoms of acute alcohol poisoning include:

- severe confusion, unpredictable behavior and stupor

- sudden lapses into and out of unconsciousness or semi-consciousness (with later alcoholic amnesia)

- vomiting while unconscious or semi-conscious

- seizures

- respiratory depression (fewer than eight breaths a minute)

- pale, bluish, cold and clammy skin due to insufficient oxygen

The cause of alcoholic hallucinosis is unclear. It seems to be highly related to the presence of dopamine in the limbic system with the possibility of other systems. There are many symptoms that could possibly occur before the hallucinations begin. Symptoms include headache, dizziness, irritability, insomnia, and indisposition. Typically, alcoholic hallucinosis has a sudden onset.

Delirium tremens (DTs) is a rapid onset of confusion usually caused by withdrawal from alcohol. When it occurs, it is often three days into the withdrawal symptoms and lasts for two to three days. Physical effects may include shaking, shivering, irregular heart rate, and sweating. People may also see or hear things other people do not. Occasionally, a very high body temperature or seizures may result in death. Alcohol is one of the most dangerous drugs from which to withdraw.

Delirium tremens typically only occurs in people with a high intake of alcohol for more than a month. A similar syndrome may occur with benzodiazepine and barbiturate withdrawal. Withdrawal from stimulants such as cocaine does not have major medical complications. In a person with delirium tremens it is important to rule out other associated problems such as electrolyte abnormalities, pancreatitis, and alcoholic hepatitis.

Prevention is by treating withdrawal symptoms. If delirium tremens occurs, aggressive treatment improves outcomes. Treatment in a quiet intensive care unit with sufficient light is often recommended. Benzodiazepines are the medication of choice with diazepam, lorazepam, chlordiazepoxide, and oxazepam all commonly used. They should be given until a person is lightly sleeping. The antipsychotic haloperidol may also be used. The vitamin thiamine is recommended. Mortality without treatment is between 15% and 40%. Currently death occurs in about 1% to 4% of cases.

About half of people with alcoholism will develop withdrawal symptoms upon reducing their use. Of these, three to five percent develop DTs or have seizures. The name delirium tremens was first used in 1813; however, the symptoms were well described since the 1700s. The word "delirium" is Latin for "going off the furrow," a plowing metaphor. It is also called shaking frenzy and Saunders-Sutton syndrome. Nicknames include the shakes, barrel-fever, blue horrors, bottleache, bats, drunken horrors, elephants, gallon distemper, quart mania, and pink spiders, among others.

Potomania, also known as beer potomania, beer drinker's potomania, and beer drinker's hyponatremia, is a specific hypo-osmolality syndrome related to massive consumption of beer, which is poor in solutes and electrolytes. With little food or other sources of electrolytes, consumption of large amounts of beer or other dilute alcoholic drinks leads to electrolyte disturbances, where the body does not have enough of nutrients known as electrolytes, namely sodium, potassium, and magnesium. The symptoms of potomania are similar to other causes of hyponatremia and include dizziness, muscular weakness, neurological impairment and seizures, all related to hyponatremia and hypokalaemia. While the symptoms of potomania are similar to other causes of hyponatremia and acute water intoxication, it should be considered an independent clinical entity because of its often chronic nature of onset, pathophysiology, and presentation of symptoms.

Alcohol intoxication, also known as drunkenness among other names, is a physiological condition that may result in psychological alterations of consciousness. Drunkenness is induced by the ingestion or consumption of alcohol in a living body. Alcohol intoxication is the result of alcohol entering the bloodstream faster than it can be metabolized by the body. Metabolism results in breaking down the ethanol into non-intoxicating byproducts.

Some effects of alcohol intoxication, such as euphoria and lowered social inhibition, are central to alcohol's desirability as a beverage and its history as one of the world's most widespread recreational drugs. Despite this widespread use and alcohol's legality in most countries, many medical sources tend to describe any level of alcohol intoxication as a form of poisoning due to ethanol's damaging effects on the body in large doses. Some religions consider alcohol intoxication to be a sin.

Symptoms of alcohol intoxication include euphoria, flushed skin, and decreased social inhibition at lower doses, with larger doses producing progressively severe impairments of balance, and decision-making ability as well as nausea or vomiting from alcohol's disruptive effect on the semicircular canals of the inner ear and chemical irritation of the gastric mucosa.

Sufficiently extreme levels of blood-borne alcohol may result in coma or death.

Toxic encephalopathy is a neurologic disorder caused by exposure to neurotoxic organic solvents such as toluene, following exposure to heavy metals such as manganese; or exposure to extreme concentrations of any natural toxin such as cyanotoxins found in shellfish or freshwater cyanobacteria crusts. Toxic encephalopathy can occur following acute or chronic exposure to neurotoxicants, which includes all natural toxins. Exposure to toxic substances can lead to a variety of symptoms, characterized by an altered mental status, memory loss, and visual problems. Toxic encephalopathy can be caused by various chemicals, some of which are commonly used in everyday life, or cyanotoxins which are bio-accumulated from Harmful algal blooms (HAB's) which have settled on the benthic layer of a waterbody. Toxic encephalopathy can permanently damage the brain and currently treatment is mainly just for the symptoms.

"Encephalopathy" is a general term describing brain malfunctions and "toxic" asserts that the malfunction is caused by toxins on the brain. The most prominent characteristic of toxic encephalopathy is an altered mental status. Acute intoxication is a reversible symptom of exposure to many synthetic chemical neurotoxicants. Acute intoxication symptoms include lightheadedness, dizziness, headache and nausea, and regular cumulative exposure to these toxic solvents over a number of years puts the individual at high risk for developing toxic encephalopathy. Chronic exposure to low levels of neurotoxic chemicals can also cause reversible changes in mood and affect which resolve with cessation of exposure. Acute and chronic toxic encephalopathy on the other hand, are persistent changes in neurological function that typically occur with exposure to higher concentrations and longer durations respectively. The symptoms of acute and chronic toxic encephalopathy do not resolve with cessation of exposure and can include memory loss, small personality changes/increased irritability, insidious onset of concentration difficulties, involuntary movements (parkinsonism), fatigue, seizures, arm strength problems, and depression. Neurobehavioral effects of occupational exposure to organic solvents exists among painters. The condition may also be referred to as substance-induced persistent dementia.

Magnetic Resonance Imaging (MRI) analyses have also demonstrated increased rates of dopamine synthesis in the putamen, reduced anterior and total corpus callosum volume, demyelination in the parietal white matter, basal ganglia, and thalamus, as well as atypical activation of frontal areas of the brain due to neural compensation. A thorough and standard diagnostic process is paramount with toxic encephalopathy, including a careful occupational history, medical history, and standardized imaging/neurobehavioral testing.

Cocaine increases alertness, feelings of well-being, euphoria, energy, competence, sociability, and sexuality. Common side effects include anxiety, increased temperature, paranoia, restlessness, and teeth grinding. With prolonged use, the drug can cause insomnia, anorexia, tachycardia, hallucinations, and paranoid delusions. Possible lethal side effects include rapid heartbeat, abnormal heart rhythms, tremors, convulsions, markedly increased core temperature, renal failure, heart attack, stroke and heart failure.

Depression with suicidal ideation may develop in heavy users. Finally, a loss of vesicular monoamine transporters, neurofilament proteins, and other morphological changes appear to indicate a long-term damage to dopamine neurons. Chronic intranasal usage can degrade the cartilage separating the nostrils (the septum nasi), which can eventually lead to its complete disappearance.

Studies have shown that cocaine usage during pregnancy triggers premature labor and may lead to abruptio placentae.

An alcohol enema, also known colloquially as butt-chugging, is the act of introducing alcohol into the rectum and colon via the anus. This method of alcohol consumption can be dangerous and even deadly because it leads to faster intoxication since the alcohol is absorbed directly into the bloodstream and neutralizes the body's ability to reject the toxin by vomiting.

Cobalt poisoning is intoxication caused by excessive levels of cobalt in the body. Cobalt is an essential element for health in animals in minute amounts as a component of Vitamin B. A deficiency of cobalt, which is very rare, is also potentially lethal, leading to pernicious anemia.

The normal human kidney, through suppression of anti-diuretic hormone, is normally able to excrete vast amounts of dilute urine. Thus a normal adult can drink up to 20 liters per day of water without becoming hyponatremic. However, the intake of solutes is also necessary to excrete free water. Under normal circumstances, this is clinically irrelevant. In the lack of proper solute intake, the amount of free water excretion can be severely limited. Without adequate solute intake, the normal functioning electrolyte gradient that pulls water into urine will be effectively destroyed.

Briefly, to excrete free water from urine, the urine flow (which is solute clearance + free water clearance) will equal the rate of solute excretion divided by the urine osmolality. With a diet of only solute poor beer, only about 200-300 mOSM (normal 750 mOSM to greater than 900 mOSM) of solute will be excreted per day, capping the amount of free water excretion at four liters. Any intake above 4 liters would lead to a dilution of the serum sodium concentration and thus hyponatremia.

Any vomiting or GI absorptive problems due to alcohol intoxication can also compound the effect of potomania due to additional electrolyte and acid-base disturbances.

Cocaine intoxication refers to the immediate and deleterious effects of cocaine on the body. Although cocaine intoxication and cocaine dependence can be present in the same individual, these syndromes present with different symptoms.

A drug-related blackout is a phenomenon caused by the intake of any substance or medication in which short term and long term memory creation is impaired, therefore causing a complete inability to recall the past. Blackouts are most frequently associated with GABAergic drugs. Blackouts are frequently described as having effects similar to that of anterograde amnesia, in which the subject cannot recall any events after the event that caused amnesia. Research on alcohol blackouts was begun by E. M. Jellinek in the 1940s. Using data from a survey of Alcoholics Anonymous (AA) members, he came to believe that blackouts would be a good determinant of alcoholism. However, there are conflicting views whether this is true. The negative psychological effects of an alcohol-related blackout are often worsened by those who suffer from anxiety disorders. Impairment of the liver will also allow more alcohol to reach the brain and hasten the individual's blackout.

The term "blackout" can also refer to a complete loss of consciousness, or syncope.

Exposure to cobalt metal dust is most common in the fabrication of tungsten carbide. Another potential source is wear and tear of metal-on-metal hip prostheses; however, this is a relatively uncommon phenomenon with 18 reported cases being documented in the medical literature.

Besides peripheral neuropathy (presenting as paresthesia or itching, burning or pain) and discoloration, swelling (edema) and desquamation may occur.

Since mercury blocks the degradation pathway of catecholamines, epinephrine excess causes profuse sweating (diaphora), tachycardia, salivation and elevated blood pressure. Mercury is suggested to inactivate S-adenosyl-methionine, which is necessary for catecholamine catabolism by catechol-o-methyl transferase.

Affected children may show red cheeks and nose, red (erythematous) lips, loss of hair, teeth, and nails, transient rashes, hypotonia and photophobia. Other symptoms may include kidney dysfunction (e.g. Fanconi syndrome) or neuropsychiatric symptoms (emotional lability, memory impairment, insomnia).

Thus, the clinical presentation may resemble pheochromocytoma or Kawasaki disease.

There is some evidence that the same mercury poisoning may predispose to Young's syndrome (men with bronchiectasis and low sperm count).

Alcohol (also known as ethanol) has a number of effects on health. Short-term effects of alcohol consumption include intoxication and dehydration. Long-term effects of alcohol consumption include changes in the metabolism of the liver and brain and alcoholism. Alcohol intoxication affects the brain, causing slurred speech, clumsiness, and delayed reflexes. Alcohol stimulates insulin production, which speeds up glucose metabolism and can result in low blood sugar, causing irritability and possibly death for diabetics. A 2014 World Health Organization report found that harmful alcohol consumption caused about 3.3 million deaths annually worldwide.

However, some effects of alcohol consumption are beneficial. Although even moderate alcohol consumption increased the risk of death in younger people, it has been shown to "decrease" the risk of death for individuals ages 55+ (due to decreased risk of ischemic heart disease).

The median lethal dose of alcohol in test animals is a blood alcohol content of 0.45%. This is about six times the level of ordinary intoxication (0.08%), but vomiting or unconsciousness may occur much sooner in people who have a low tolerance for alcohol. The high tolerance of chronic heavy drinkers may allow some of them to remain conscious at levels above 0.40%, although serious health hazards are incurred at this level.

Alcohol also limits the production of vasopressin (ADH) from the hypothalamus and the secretion of this hormone from the posterior pituitary gland. This is what causes severe dehydration when alcohol is consumed in large amounts. It also causes a high concentration of water in the urine and vomit and the intense thirst that goes along with a hangover.

Stress, hangovers, and the oral contraceptive pill may increase the desire for alcohol because these things will lower the level of testosterone and alcohol will acutely elevate it. Tobacco has the same effect of increasing the craving for alcohol.

Alcohol tolerance refers to the bodily responses to the functional effects of ethanol in alcoholic beverages. This includes direct tolerance, speed of recovery from insobriety and resistance to the development of alcoholism.