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Diagnosis of poisoning
Last reviewed: 06.07.2025
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The first stage of poisoning diagnosis is an assessment of the patient's general condition. Severe poisoning may require emergency measures to treat acute cardiovascular failure (collapse).
The history of poisoning may be known on admission. In patients with unexplained symptoms, especially changes in consciousness, poisoning should be suspected. Deliberate self-poisoning in adults suggests the possibility of using more than one poisoning agent. History sometimes plays a major role. Since many patients are unable to provide reliable information (young children, patients with impaired consciousness, adults after a suicide attempt or with psychosis), friends, relatives, and emergency or rescue personnel should be interviewed. Even patients who appear trustworthy may be inaccurate in describing the time of ingestion and the amount of poison ingested. If possible, the patient's home should be inspected for clues (half-empty medication containers, signs of abuse). The patient's medical record and prescriptions may be helpful. If poisoning at work cannot be ruled out, co-workers and management should be interviewed. All chemical plants should have detailed toxicity data and specific treatments directly at the workplace.
In the United States, Europe, and some countries in Asia and South America, information about industrial and household chemicals can be obtained from Poison Control Centers. Consulting with a Poison Control Center is helpful because information printed on the chemical's packaging about its ingredients, first aid, and antidotes may be out of date or inaccurate. In addition, the contents of the container may have been substituted or the packaging may have been damaged. Poison Control Centers can help identify unknown pills by appearance and may also provide consultation with a toxicologist. The phone number for the nearest center can be found, along with other emergency numbers, on the front page of your local telephone directory, through your carrier, or in the United States by dialing 1-800-222-1222.
During a clinical examination, it is possible to identify symptoms characteristic of poisoning with a certain poison (specific odor, injection tracks during intravenous administration of drugs, signs of chronic alcoholism).
It is necessary to take into account that even in case of poisoning, disorders of consciousness can be caused by other reasons (infectious lesion of the central nervous system, traumatic brain injury, hypoglycemia, stroke, hepatic encephalopathy, Wernicke's encephalopathy). In case of poisoning with drugs in older children, adolescents and adults, it is necessary to remember the possibility of a suicide attempt. After stabilization of the condition, they need to consult a psychiatrist.
[ Laboratory diagnostics of poisoning
In most cases, laboratory tests are of little use. Standard, readily available tests for commonly abused drugs provide only qualitative, not quantitative, information. These tests can produce false positives and detect a limited number of substances. In addition, the presence of such a drug in a patient’s blood or urine does not necessarily mean that it is the one causing the clinical manifestations of poisoning.
The concentration of most substances in the blood is difficult to determine, and this indicator does not always influence the treatment tactics. In case of poisoning with some drugs (e.g. paracetamol, acetylsalicylic acid, CO, digoxin, ethylene glycol, iron, lithium, methanol, phenobarbital, theophylline), the concentration in the blood helps to choose the treatment. Many specialists recommend measuring the concentration of paracetamol in the blood of all patients with mixed poisoning, since paracetamol poisoning in the early stages is often asymptomatic, can cause serious long-term consequences that can be prevented by administering an antidote. For some substances, other blood tests can help in choosing the treatment (e.g. PTI/INR in case of warfarin overdose, determination of the methemoglobin content in the blood in some poisonings). In patients with impaired consciousness or vital functions (cardiac, pulmonary, etc.), as well as in cases of poisoning with certain toxins, it is necessary to determine plasma electrolytes, creatinine, glucose, blood nitrogen content, osmolarity, and arterial blood gas composition. In specific poisonings, other laboratory tests may also be indicated.
In certain poisonings (e.g., iron, lead, arsenic, other metals, or suspected rupture of a packet of cocaine or other drug ingested by the carrier "swallower"), plain abdominal radiography may help localize what has been ingested. Radiography is also indicated in patients with serious symptoms suggesting possible poisoning by an unknown poison.
In case of poisoning with drugs that affect the cardiovascular system or unknown drugs, it is necessary to conduct an ECG and cardiac monitoring.
If the concentration of a substance increases after its initial decrease, or if symptoms of poisoning persist for an unusually long time, bezoars, long-acting drug poisoning, or repeated exposure (repeated abuse) should be considered.