A specific blood test to verify toxicity is not typically available. An electrocardiogram (ECG) should be included in the assessment when there is concern of an overdose.

People with symptoms are usually monitored in an intensive care unit for a minimum of 12 hours, with close attention paid to maintenance of the airways, along with monitoring of blood pressure, arterial pH, and continuous ECG monitoring. Supportive therapy is given if necessary, including respiratory assistance and maintenance of body temperature. Once a person has had a normal ECG for more than 24 hours they are generally medically clear.

The diagnosis of benzodiazepine overdose may be difficult, but is usually made based on the clinical presentation of the patient along with a history of overdose. Obtaining a laboratory test for benzodiazepine blood concentrations can be useful in patients presenting with CNS depression or coma of unknown origin. Techniques available to measure blood concentrations include thin layer chromatography, gas liquid chromatography with or without a mass spectrometer, and radioimmunoassay. Blood benzodiazepine concentrations, however, do not appear to be related to any toxicological effect or predictive of clinical outcome. Blood concentrations are, therefore, used mainly to confirm the diagnosis rather than being useful for the clinical management of the patient.

The substance that has been taken may often be determined by asking the person. However, if they will not, or cannot, due to an altered level of consciousness, provide this information, a search of the home or questioning of friends and family may be helpful.

Examination for toxidromes, drug testing, or laboratory test may be helpful. Other laboratory test such as glucose, urea and electrolytes, paracetamol levels and salicylate levels are typically done. Negative drug-drug interactions have sometimes been misdiagnosed as an acute drug overdose, occasionally leading to the assumption of suicide.

Paracetamol may be quantified in blood, plasma, or urine as a diagnostic tool in clinical poisoning situations or to aid in the medicolegal investigation of suspicious deaths. The concentration in serum after a typical dose of paracetamol usually peaks below 30 mg/l, which equals 200 µmol/L. Levels of 30–300 mg/L (200–2000 µmol/L) are often observed in overdose patients. Postmortem blood levels have ranged from 50–400 mg/L in persons dying due to acute overdosage. Automated colorimetric techniques, gas chromatography and liquid chromatography are currently in use for the laboratory analysis of the drug in physiological specimens.

A person's history of taking paracetamol is somewhat accurate for the diagnosis. The most effective way to diagnose poisoning is by obtaining a blood paracetamol level. A drug nomogram developed in 1975, called the Rumack-Matthew nomogram, estimates the risk of toxicity based on the serum concentration of paracetamol at a given number of hours after ingestion. To determine the risk of potential hepatotoxicity, the paracetamol level is traced along the nomogram. Use of a timed serum paracetamol level plotted on the nomogram appears to be the best marker indicating the potential for liver injury. A paracetamol level drawn in the first four hours after ingestion may underestimate the amount in the system because paracetamol may still be in the process of being absorbed from the gastrointestinal tract. Therefore, a serum level taken before 4 hours is not recommended.

Clinical or biochemical evidence of liver toxicity may develop in one to four days, although, in severe cases, it may be evident in 12 hours. Right-upper-quadrant tenderness may be present and can aid in diagnosis. Laboratory studies may show evidence of liver necrosis with elevated AST, ALT, bilirubin, and prolonged coagulation times, particularly an elevated prothrombin time. After paracetamol overdose, when AST and ALT exceed 1000 IU/L, paracetamol-induced hepatotoxicity can be diagnosed. In some cases, the AST and ALT levels can exceed 10,000 IU/L.

The level of digoxin for treatment is typically 0.5-2 ng/mL. Since this is a narrow therapeutic index, digoxin overdose can happen. A serum digoxin concentration of 0.5-0.9 ng/mL among those with heart failure is associated with reduced heart failure deaths and hospitalizations. It is therefore recommended that digoxin concentration be maintained in approximately this range if it is used in heart failure patients.

High amounts of the electrolyte potassium (K+) in the blood (hyperkalemia) is characteristic of digoxin toxicity. Digoxin toxicity increases in individuals who have kidney impairment. This is most often seen in elderly or those with chronic renal insufficiency or end-stage kidney disease.

Stabilization of the victim's airway, breathing, and circulation (ABCs) is the initial treatment of an overdose. Ventilation is considered when there is a low respiratory rate or when blood gases show the person to be hypoxic. Monitoring of the patient should continue before and throughout the treatment process, with particular attention to temperature, pulse, respiratory rate, blood pressure, urine output, electrocardiography (ECG) and O saturation. Poison control centers and medical toxicologists are available in many areas to provide guidance in overdoses to both physicians and the general public.

Medical observation and supportive care are the mainstay of treatment of benzodiazepine overdose. Although benzodiazepines are absorbed by activated charcoal, gastric decontamination with activated charcoal is not beneficial in pure benzodiazepine overdose as the risk of adverse effects would outweigh any potential benefit from the procedure. It is recommended only if benzodiazepines have been taken in combination with other drugs that may benefit from decontamination. Gastric lavage (stomach pumping) or whole bowel irrigation are also not recommended. Enhancing elimination of the drug with hemodialysis, hemoperfusion, or forced diuresis is unlikely to be beneficial as these procedures have little effect on the clearance of benzodiazepines due to their large volume of distribution and lipid solubility.

Efforts to prevent poisoning include child-resistant packaging and a lower number of pills per package.

The primary treatment of digoxin toxicity is digoxin immune fab, which is an antibody made up of anti-digoxin immunoglobulin fragments. This antidote has been shown to be highly effective in treating life-threatening signs of digoxin toxicity such as hyperkalemia, hemodynamic instability, and arrhythmias. Fab dose can be determined by two different methods. First method is based on the amount of digoxin ingested whereas the second method is based on the serum digoxin concentration and the weight of the person.

Other treatment that may be used to treat life-threatening arrhythmias until Fab is acquired are magnesium, phenytoin, and lidocaine. Magnesium suppresses digoxin-induced ventricular arrhythmias while phenytoin and lidocaine suppresses digoxin-induced ventricular automaticity and delay afterdepolarizations without depressing AV conduction. In the case of an abnormally slow heart rate (bradyarrhythmias), Atropine, catecholamines (isoprenaline or salbutamol), and/or temporary cardiac pacing can be used.

Intravenous fluids containing dextrose such as D5W are recommended to keep a urinary output between 2 and 3 ml/kg/h.

Sodium bicarbonate is given in a significant aspirin overdose (salicylate level greater than 35 mg/dl 6 hours after ingestion) regardless of the serum pH, as it enhances elimination of aspirin in the urine. It is given until a urine pH between 7.5 and 8.0 is achieved.

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.

ADT tachyphylaxis specifically occurs in depressed patients using SSRIs and MAOIs. Currently, SSRIs are the preferred treatment for depression among clinicians, as MAOIs require the patient to avoid certain foods and other medications due to the potential for interactions capable of inducing dangerous side effects. Provided is a list of medications known to be subject to Poop-out.

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.

The absence of a pulse confirms a clinical diagnosis of cardiac arrest, but PEA can only be distinguished from other causes of cardiac arrest with a device capable of electrocardiography (ECG/EKG). In PEA, there is organised or semi-organised electrical activity in the heart as opposed to asystole (flatline)or to the disorganised electrical activity of either ventricular fibrillation or ventricular tachycardia.

These headaches are treated by determining the cause of the headache and treating or removing this cause

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.

The following guideline values (ppm values rounded) and periods of time-weighted average exposures have been determined in such a way that the carboxyhaemoglobin (COHb) level of 2.5% is not exceeded, even when a normal subject engages in light or moderate exercise:

- 100 mg/m3 (87 ppm) for 15 min

- 60 mg/m3 (52 ppm) for 30 min

- 30 mg/m3 (26 ppm) for 1 h

- 10 mg/m3 (9 ppm) for 8 h

For indoor air quality 7 mg/m3 (6 ppm) for 24 h (so as not to exceed 2% COHb for chronic exposure)

Following a declination or total extinction in response to a previously therapeutic dose of an antidepressant, the issue is clinically addressed as stemming from tolerance development. Several strategies are available, such as exploring drug options from a different drug class used to treat depression. The patient can also choose to switch to another SSRI (or MAOI, if applicable) while maintaining proportionate dose. If tolerance develops in a drug from the same class, the clinician may recommend a regular cycle consisting of all effective treatments within the SSRI or MAOI classes, in order to minimize transitional side effects while maximizing therapeutic efficacy.

Other options include increasing dose of the same medication, or supplementation with another antidepressant. Dual reuptake inhibitors, also known as tricyclic antidepressants have been shown to have lower rates of tachyphylaxis.

Upon the discontinuation of serotonergic drugs, most cases of serotonin syndrome resolve within 24 hours, although in some cases delirium may persist for a number of days. Symptoms typically persist for a longer time frame in patients taking drugs which have a long elimination half-life, active metabolites, or a protracted duration of action.

Cases have reported muscle pain and weakness persisting for months, and antidepressant discontinuation may contribute to ongoing features. Following appropriate medical management, serotonin syndrome is generally associated with a favorable prognosis.

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.

Symptoms can last for more than 4 weeks and typically resolve within a day of restoring the medication.

There is no laboratory test for serotonin syndrome. Therefore, diagnosis is by symptom observation and investigation of the patient's history. Several diagnostic criteria have been proposed. The first rigorously evaluated criteria were introduced in 1991 by Harvey Sternbach, a professor of psychiatry at UCLA. Researchers in Australia later developed the Hunter Toxicity Criteria Decision Rules, which have better sensitivity and specificity, 84% and 97%, respectively, when compared with the gold standard of diagnosis by a medical toxicologist. As of 2007, Sternbach's criteria were still the most commonly used.

The most important symptoms for diagnosing serotonin syndrome are tremor, extreme aggressiveness, akathisia, or clonus (spontaneous, inducible and ocular). Physical examination of the patient should include assessment of deep-tendon reflexes and muscle rigidity, the dryness of the mucosa of the mouth, the size and reactivity of the pupils, the intensity of bowel sounds, skin color, and the presence or absence of sweating. The patient's history also plays an important role in diagnosis, investigations should include inquiries about the use of prescription and over-the-counter drugs, illicit substances, and dietary supplements, as all these agents have been implicated in the development of serotonin syndrome. To fulfill the Hunter Criteria, a patient must have taken a serotonergic agent and meet one of the following conditions:

- Spontaneous clonus, or

- Inducible clonus plus agitation or diaphoresis, or

- Ocular clonus plus agitation or diaphoresis, or

- Tremor plus hyperreflexia, or

- Hypertonism plus temperature > plus ocular clonus or inducible clonus

Definitive diagnosis relies on a blood test for alcohol, usually performed as part of a toxicology screen.

Law enforcement officers in the United States of America often use breathalyzer units and field sobriety tests as more convenient and rapid alternatives to blood tests.

There are also various models of breathalyzer units that are available for consumer use. Because these may have varying reliability and may produce different results than the tests used for law-enforcement purposes, the results from such devices should be conservatively interpreted.

Many informal intoxication tests exist, which, in general, are unreliable and not recommended as deterrents to excessive intoxication or as indicators of the safety of activities such as motor vehicle driving, heavy equipment operation, machine tool use, etc.

For determining whether someone is intoxicated by alcohol by some means other than a blood-alcohol test, it is necessary to rule out other conditions such as hypoglycemia, stroke, usage of other intoxicants, mental health issues, and so on. It is best if his/her behavior has been observed while the subject is sober to establish a baseline. Several well-known criteria can be used to establish a probable diagnosis. For a physician in the acute-treatment setting, acute alcohol intoxication can mimic other acute neurological disorders, or is frequently combined with other recreational drugs that complicate diagnosis and treatment.