How to Tell if Someone Is on Drugs — The Signs That Distinguish Substances

Why It Matters to Know the Difference

Recognising that someone is impaired is the first step. Knowing what they're impaired by matters for two practical reasons: it affects how dangerous the situation is, and it affects what appropriate intervention looks like. Alcohol poisoning and opioid overdose both produce unconsciousness and require emergency services — but they present with different signs and, in the case of opioid overdose, respond to a specific reversing drug (naloxone) that is now widely available. Stimulant intoxication produces the opposite physiological state to opioid intoxication and carries different specific risks. Getting the identification right reduces the time to the correct intervention.

Alcohol Intoxication: The Baseline for Comparison

Alcohol intoxication is the most common form of substance impairment encountered in social settings. The characteristic signs: reduced inhibition and increased sociability progressing to coordination impairment, slurred speech, emotional volatility, and eventual sedation. The smell of alcohol on breath is usually detectable. Eyes may be glassy or slightly unfocused. The trajectory is from animated to sedated — alcohol is a depressant, and its arc runs downward toward sleep or unconsciousness.

Key distinguishing feature: pupils are normal or mildly dilated at low levels; speech is slurred due to motor impairment of articulation; coordination is compromised but the person is usually aware of their impairment at moderate levels.

Cocaine and Crack Cocaine

Cocaine and crack cocaine are stimulants — their effects are physiologically opposite to alcohol's. Rather than sedation, they produce stimulation; rather than reducing heart rate and blood pressure, they elevate both.

Observable signs: elevated energy and confidence that may appear normal but has a forced, pressured quality; rapid, pressured speech that jumps between topics; dilated pupils (a consistent sign of stimulant use — the sympathetic nervous system activation that cocaine produces causes pupil dilation regardless of lighting); elevated heart rate visible as rapid neck pulse or reported by the person; sniffling, frequent nose-touching, or nasal irritation in cocaine users (intranasal route leaves specific traces); dry mouth producing frequent lip-licking.

The risk in stimulant intoxication that distinguishes it from alcohol: cardiovascular — cocaine causes vasoconstriction and cardiac stimulation that produces real risk of cardiac arrhythmia, myocardial infarction, and stroke, particularly in people with underlying cardiovascular vulnerabilities or in combination with alcohol (which produces cocaethylene in the liver, a more cardiotoxic compound than either substance alone). Extreme agitation, chest pain, or seizures in someone showing stimulant signs are medical emergencies.

MDMA (Ecstasy)

MDMA produces a distinctive combination of stimulant and empathogen effects. Observable signs: dilated pupils; elevated heart rate and temperature; excessive sweating; increased physical energy and desire for movement; notable emotional warmth and expressiveness (the empathogen effect — unusual openness and affection); jaw clenching (bruxism) causing grinding or teeth-clenching visible as jaw movement; elevated alertness and sensory sensitivity.

MDMA-specific risks: hyperthermia (dangerously elevated body temperature, particularly in hot environments with physical activity — one of the primary causes of MDMA-related deaths); hyponatraemia (water intoxication from drinking excessive amounts of water in response to perceived dehydration advice, without adequate electrolytes — causes dangerous sodium dilution); serotonin syndrome in combination with certain medications. Someone who is overheating, confused, or having seizures after MDMA use needs emergency services.

Opioids (Heroin, Prescription Opioids, Fentanyl)

Opioid intoxication produces CNS depression, similar in some respects to alcohol but with a distinctive specific sign that makes it identifiable: pinpoint pupils. This is not seen in alcohol or stimulant intoxication and is one of the most reliable identifiers of opioid intoxication or overdose.

Observable signs of intoxication: extreme drowsiness or "nodding off" — alternating between waking and sleep in a way that doesn't resemble normal tiredness; slowed, shallow breathing; pinpoint (very small) pupils regardless of lighting; slack facial muscles and slow response to stimulation; slurred or incoherent speech; pale, clammy skin.

Opioid overdose is a medical emergency with specific intervention: naloxone (Narcan) reverses opioid overdose and is now available over the counter in many countries. Signs of overdose: unresponsive, will not wake; very slow or stopped breathing; blue or grey colouring of lips and fingertips; gurgling sound from breathing (indicating airway compromise). Call emergency services and administer naloxone if available. Recovery position while waiting. Do not leave the person alone.

Cannabis

Cannabis intoxication is less likely to produce a medical emergency but worth distinguishing. Observable signs: red or bloodshot eyes (a consistent sign from vasodilation of conjunctival vessels); slowed speech and movement; increased appetite; laughter and mild sensory enhancement; altered time perception (the person may seem confused about how much time has passed); distinct cannabis smell on clothing or breath.

High-potency cannabis can produce anxiety, paranoia, or acute psychosis in susceptible individuals — particularly in those with personal or family history of psychotic disorders. Cannabis-induced acute psychosis presents with paranoid thinking, disorganised speech, and agitation. This is not dangerous in the way opioid overdose is dangerous, but the person needs a calm environment, reassurance, and potentially medical assessment if symptoms are severe.

The Key Principles for Bystander Response

Across all substance types: unconsciousness requires emergency services, regardless of substance. Breathing assessment is the most important immediate check — slow, shallow, or absent breathing is always a medical emergency. Recovery position for anyone unconscious or semi-conscious. Don't leave impaired people alone. Don't give food or water to someone with significantly altered consciousness. Be specific when speaking to emergency services — "I think he's taken cocaine and alcohol" is more useful than "I think he's on something." You will not get someone in trouble by calling an ambulance. You might save their life.