Lysergic acid diethylamide (LSD), commonly known as acid, is a powerful semisynthetic hallucinogenic drug derived from a substance found in the ergot fungus. It is one of the most potent psychoactive substances known, producing profound alterations in perception, mood, and cognitive processes at microgram doses. Concerns about an LSD “overdose” involve two possibilities: physical fatality or a severe, dangerous psychological reaction. While a fatal physical overdose from the drug itself is rare, severe adverse reactions caused by high doses require immediate attention.
The Question of Lethal Toxicity
Scientific data indicates that LSD possesses low direct physical toxicity; the amount required to produce death is vastly greater than the amount required for a psychoactive effect. This difference is measured by the therapeutic index, which is high compared to many other substances. Estimates suggest a lethal human dose would be approximately 100 milligrams, about 1,000 times the average recreational dose of 100 micrograms.
There have been no documented human deaths attributed solely to the direct physiological toxicity of LSD at recreational doses. Fatalities linked to LSD use are nearly always secondary to complications such as accidents, dangerous behavior, or pre-existing health conditions. In rare instances of massive, accidental ingestion, individuals have consumed doses in the milligram range and suffered severe symptoms, but still survived with medical intervention. This reinforces the drug’s relatively non-toxic profile to major organs.
Acute Physical Effects of Excessive Doses
While direct lethality is uncommon, consuming an excessive dose of LSD can trigger severe, non-lethal physical responses that constitute a medical emergency. These reactions stimulate the body’s fight-or-flight response. Elevated blood pressure (hypertension) and a rapid heart rate (tachycardia) are common, but at high doses, they can become dangerously pronounced.
The most concerning physical effect is hyperthermia, or a high body temperature, which can lead to organ damage if not quickly addressed. Severe intoxication can also cause neurological complications, including seizures and coma, though these are rare. In extreme cases, the combination of agitation, hyperthermia, and muscle breakdown (rhabdomyolysis) can lead to acute kidney injury. These involuntary physiological responses require immediate medical attention to prevent lasting harm.
Understanding the Acute Psychological Crisis
The most common and distressing adverse reaction to LSD is the acute psychological crisis, often termed a “bad trip.” This crisis is characterized by overwhelming negative emotions and cognitive distortions that feel inescapable, lasting for the entire duration of the drug’s effects. Symptoms frequently include intense anxiety, severe panic attacks, and profound paranoia that may lead to delusional thinking.
A person may experience depersonalization, feeling detached from their own body, or derealization, perceiving the world as unreal or dreamlike. This loss of connection with reality can be terrifying and may result in the user engaging in erratic or dangerous behaviors. Psychological distress is the leading cause of emergency room visits related to LSD. While this crisis is not physically toxic, the resulting behavioral toxicity—such as running into traffic or jumping from a height—is the primary indirect cause of LSD-related injury or death.
Recognizing When Emergency Assistance is Needed
It is important to distinguish between a difficult experience, which can often be managed with calm reassurance, and an outright medical emergency. Certain signs indicate the need to seek immediate medical assistance by calling emergency services.
Any sign of involuntary physical danger warrants immediate professional help, including convulsions or seizures, loss of consciousness, or inability to be roused. Sustained, elevated body temperature (hyperthermia) is a warning sign that requires urgent medical intervention.
Medical help should also be summoned when a person exhibits behavior that poses an imminent risk of serious self-harm or harm to others, such as attempting to exit a moving vehicle or engaging in extreme aggression. When speaking with emergency responders, providing accurate information about the substance taken and the approximate dose allows them to prepare the most effective supportive treatment.