The signs that someone is high depend entirely on what substance they’ve used, but certain physical and behavioral changes are hard to hide. Red or glassy eyes, unusual pupil size, slurred or rapid speech, impaired coordination, and sudden shifts in mood or energy are among the most common giveaways. Knowing what to look for with specific substances makes the picture much clearer.
Cannabis (Marijuana)
Cannabis produces some of the most recognizable signs of intoxication. The classic tell is red, bloodshot eyes, caused by blood vessels in the eye expanding as blood pressure drops. This happens reliably enough that it’s one of the hallmarks clinicians use to identify recent use. Dry mouth is another consistent marker, often prompting frequent sipping of drinks or lip-licking.
Physically, heart rate increases during acute use, sometimes noticeably so. The person may seem lethargic, slow to respond, or unfocused. Concentration takes a hit, and reaction times get worse across the board. You might notice them losing track of conversations, laughing at things that aren’t particularly funny, or struggling to follow a simple sequence of tasks. Appetite typically surges (“the munchies” is real), and some people become unusually quiet or withdrawn while others get giggly and talkative. A subtle but telling sign is nystagmus, a slight involuntary flickering of the eyes that’s difficult to fake or suppress.
Stimulants: Cocaine and Amphetamines
Stimulant intoxication often looks like someone in a manic episode. Energy spikes dramatically, speech becomes fast and pressured, and the person may jump between topics without finishing a thought. They can seem unusually confident, restless, or wired, with dilated pupils and a jittery quality to their movements.
With higher doses, judgment deteriorates. Hypersexuality, impulsive decision-making, and paranoia can emerge. Methamphetamine in particular produces distinctive repetitive behaviors: picking at skin, obsessively disassembling and reassembling objects, or cleaning the same spot over and over. People who use meth chronically often develop noticeable suspiciousness, pulling away from social interaction and misinterpreting neutral situations as threatening.
Cocaine tends to produce shorter bursts of these effects, cycling between intense highs and crashes. You might notice someone excusing themselves frequently (to re-dose), sniffling or rubbing their nose, and swinging between extreme confidence and irritability. Problem-solving and abstract thinking suffer even when the person feels sharper than usual.
At the extreme end, stimulant-induced psychosis can develop. This looks like intense paranoia, seeing shadows or figures in peripheral vision, and hearing voices, typically ones saying negative things about the person. This is a serious state that can escalate quickly.
Opioids: Heroin, Fentanyl, and Painkillers
Opioid intoxication is in many ways the opposite of stimulant use. The person becomes heavily sedated, with drooping eyelids and a characteristic “nodding off,” where the head drops forward and then snaps back up repeatedly. Pupils constrict to tiny pinpoints, which is one of the most reliable physical markers of opioid use regardless of the specific drug.
Speech becomes slow and slurred, body temperature drops slightly, and the person may seem deeply relaxed or almost dreamlike in their demeanor. Their movements are sluggish and uncoordinated. They might scratch their face or body frequently, since opioids trigger histamine release that causes itching.
The line between a strong opioid high and a medical emergency can be thin. Breathing that becomes very slow, shallow, or irregular is the critical warning sign. If someone is unresponsive, making gurgling sounds, or their lips or fingertips turn bluish, that’s no longer intoxication. That’s an overdose.
Hallucinogens and Dissociatives
Someone on a hallucinogen like LSD or psilocybin mushrooms may be the hardest to identify from physical signs alone, since the most dramatic effects are internal. The hallmark is profound changes in perception: the person might stare at ordinary objects with fascination, describe colors as more vivid, or react to visual distortions that aren’t there. Most perceptual changes are visual, though sounds and physical sensations can also feel amplified or distorted.
Pupils dilate significantly on classic hallucinogens. The person may seem emotionally volatile, swinging between wonder, anxiety, and confusion. Conversations can become disjointed or philosophical in ways that don’t track logically. Physical coordination stays relatively intact compared to other substances, but the person may move cautiously, as if navigating an unfamiliar environment.
Dissociatives like ketamine produce a different picture. The person may appear detached or “not all there,” with a blank or distant expression. At higher doses, they can become nearly unresponsive, entering what’s sometimes called a “k-hole,” a state of deep disconnection from their body and surroundings. Speech becomes garbled, and balance deteriorates significantly.
Alcohol and Sedatives
Alcohol intoxication is familiar to most people, but sedative medications like benzodiazepines produce a very similar picture: slurred speech, impaired balance, slowed reflexes, and emotional disinhibition. The person may say things they normally wouldn’t, become unusually affectionate or aggressive, and struggle with basic coordination like walking in a straight line.
Benzodiazepines and similar sedatives are particularly associated with drug-induced ataxia, a clinical term for the loss of smooth, coordinated movement. This tends to appear within days or weeks of starting or increasing a dose and usually reverses once the substance clears the system. Combining sedatives with alcohol is especially dangerous, as this combination significantly increases the risk of consciousness impairment and the need for emergency care.
General Signs Across Substances
Some patterns cut across drug categories and are worth knowing regardless of what someone might have taken:
- Pupil changes. Dilated pupils suggest stimulants, hallucinogens, or MDMA. Constricted (pinpoint) pupils point toward opioids. Cannabis doesn’t change pupil size much but does make the whites of the eyes red.
- Speech patterns. Rapid, pressured speech suggests stimulants. Slow, slurred speech suggests depressants or opioids. Disorganized, tangential speech can indicate hallucinogens or high-dose cannabis.
- Energy and movement. Hyperactivity and restlessness point to stimulants. Sedation and slow movement point to depressants or opioids. Unsteady gait is common with alcohol, sedatives, and dissociatives.
- Mood shifts. Sudden euphoria, uncharacteristic confidence, or unexplained paranoia and irritability can all signal intoxication, depending on the substance.
When Intoxication Becomes an Emergency
Most intoxication episodes are self-limiting. The person feels the effects, the substance wears off, and they return to baseline without medical intervention. But certain signs cross into dangerous territory. Mixing substances, especially combining anything with alcohol, dramatically increases the risk of serious complications including deeper loss of consciousness, breathing problems, and longer recovery times.
The clearest red flags are unresponsiveness (you can’t wake the person or get them to respond), breathing that has slowed to a rate that seems abnormal, seizures, chest pain, or a body temperature that feels extremely high or low. Severe psychomotor agitation, where someone is thrashing, extremely confused, and can’t be calmed, also warrants emergency attention. These situations are not just “being really high.” They represent physiological crises where minutes matter.