The signs that someone is high depend heavily on what substance they’re using, but a few things are almost universal: changes in pupil size, unusual shifts in energy or mood, and behavior that doesn’t match the situation. Some signs are subtle enough to miss if you’re not paying attention, while others are impossible to ignore. Here’s what to look for, broken down by the type of substance involved.
Eyes Are the Most Reliable Indicator
The eyes reveal more about intoxication than almost any other part of the body, because pupil size is controlled by the same part of the nervous system that drugs act on. Stimulants like cocaine and amphetamines cause the pupils to dilate noticeably, even in well-lit rooms where they should be small. Opioids do the opposite, shrinking pupils down to tiny pinpoints that barely react to changes in light. If someone’s pupils look wrong for the lighting they’re in, that’s one of the strongest clues available.
Eye movement matters too. Alcohol, inhalants, and certain dissociative drugs interfere with the brain’s ability to smoothly control eye tracking. You might notice someone’s eyes jerking or bouncing involuntarily when they try to look to the side. At high doses of alcohol or inhalants, this jerking can happen even when the eyes move up and down. Bloodshot or glassy eyes are a more general sign that shows up across many substances, from alcohol to marijuana.
Signs of Stimulant Use
Stimulants like cocaine, methamphetamine, and prescription amphetamines push the body into overdrive. Someone who’s high on a stimulant will often seem unusually energetic, talkative, or wired. They may talk faster than normal, jump between topics, or seem unable to sit still. Physically, you might notice a rapid heartbeat (visible as a pulsing vein in the neck), sweating, jaw clenching, or teeth grinding.
Restless, repetitive movements are a hallmark. This can look like foot-tapping, pacing, picking at skin or clothing, fiddling with objects, or wringing hands. These movements tend to be aimless and unproductive, almost mechanical. At higher doses, agitation can escalate into paranoia, where the person seems fearful or suspicious without any clear reason. Dilated pupils, decreased appetite, and going unusually long stretches without sleep are other common giveaways.
Signs of Opioid Use
Opioids produce a distinctly different picture. Instead of energy and alertness, you’ll see drowsiness, slowed speech, and a relaxed or “foggy” demeanor. The classic sign is what’s sometimes called “nodding out,” where the person drifts in and out of consciousness, their head drooping forward before they catch themselves. Pinpoint pupils are present in most cases, though a few specific opioids can leave pupils normal-sized or even slightly enlarged.
Breathing is the critical thing to watch. Opioids suppress the brain’s drive to breathe, and in moderate to severe intoxication, breathing rates can drop to as low as four to six breaths per minute. Normal resting breathing is 12 to 20 breaths per minute, so this is a dramatic slowdown. Shallow, slow, or irregular breathing in someone who seems heavily sedated is a medical emergency, not just a sign of being high.
Other signs include slurred speech, constipation (if use is ongoing), itching or frequent nose-rubbing, and a general sense of emotional detachment or unusual calm.
Signs of Marijuana Use
Marijuana produces some of the most recognizable signs: red or bloodshot eyes, a strong herbal smell on clothes or breath, and a noticeable shift in mood. Someone who’s high on marijuana may laugh more easily, seem spaced out, lose track of conversations, or react to things more slowly than usual. Increased appetite is common, along with dry mouth and a tendency to fixate on food, music, or sensory experiences.
At higher doses, marijuana can cause anxiety, paranoia, or withdrawal from conversation. The person might seem unusually quiet, self-conscious, or uncomfortable in social settings where they’d normally be fine. Coordination can be mildly impaired, and short-term memory often takes a noticeable hit, with the person forgetting what they were saying mid-sentence.
Signs of Alcohol Intoxication
Most people can recognize obvious drunkenness, but earlier stages are easier to miss. The progression typically starts with loosened inhibitions, louder speech, and a flushed face. As intoxication deepens, slurred speech, unsteady walking, and impaired judgment become more obvious. The person may repeat themselves, make poor decisions, become emotionally volatile, or have trouble focusing their eyes.
Alcohol disrupts the nervous system’s ability to fine-tune motor control, affecting everything from hand coordination to posture to eye movements. Someone who seems slightly “off” in their balance or coordination, even if they’re not stumbling, may be more intoxicated than they appear.
Signs of Sedative or “Downer” Use
Benzodiazepines, barbiturates, and newer substances like xylazine (sometimes called “tranq”) produce heavy sedation that can look similar to opioid intoxication but with some differences. The person may appear extremely drowsy, confused, or disoriented, with slurred speech and poor coordination. Xylazine, which has become increasingly common as an additive in the illicit drug supply, causes particularly deep sedation along with dangerously low blood pressure and slowed heart rate.
One distinctive marker of xylazine use is the development of skin wounds, often on the arms or legs, that don’t heal normally and can worsen rapidly. These wounds can appear even at injection sites far from where the drug was administered, making them unusual compared to typical injection-related injuries. If someone you know has unexplained, slow-healing sores alongside signs of heavy sedation, xylazine exposure is a real possibility.
Behavioral and Contextual Clues
Physical signs are important, but behavioral changes often tell you just as much. Look for sudden, unexplained shifts in personality or routine. Someone who’s normally social becoming withdrawn, or someone who’s usually calm becoming hyperactive, can signal substance use. Frequent disappearances (to the bathroom, outside, to their car) followed by noticeable mood or energy changes are a common pattern.
Other contextual clues include unusual smells (chemical, sweet, or herbal), drug paraphernalia like pipes, lighters with burn marks, small baggies, or rolled-up bills, and physical evidence like burn marks on fingers or lips. Changes in sleep patterns, appetite, personal hygiene, and social circles over weeks or months suggest ongoing use rather than a single episode.
Keep in mind that many of these signs overlap with medical conditions, mental health issues, or simple fatigue. Pinpoint pupils can result from certain medications. Dilated pupils can come from dim lighting or excitement. Slurred speech can be a sign of a stroke. No single sign is definitive on its own, and the more signs you observe together, the more confident you can be in what you’re seeing.
What Different Combinations Look Like
In practice, people often use more than one substance at a time, which creates mixed signals. Someone using opioids and stimulants together might have pupils that are neither clearly pinpointed nor fully dilated. Someone drinking alcohol while on a sedative will appear far more intoxicated than either substance alone would explain. The general rule is to focus on the overall picture: Is this person’s level of alertness, coordination, and behavior normal for them and for the situation? If something feels clearly off, trust that observation even if the specific substance isn’t obvious.