Substance abuse rarely announces itself all at once. It shows up in small, accumulating changes: a shift in someone’s appearance, a personality that feels slightly off, new habits that don’t quite add up. Knowing what to look for can help you recognize a problem early, when intervention is most effective. The signs fall into a few distinct categories, and the more of them you notice in the same person, the stronger the signal.
Physical Changes to Watch For
The body responds to regular substance use in visible ways, and many of these changes are hard to hide. Eyes are one of the most reliable indicators. Stimulants like cocaine and methamphetamine cause pupils to become noticeably larger than usual, while opioid painkillers do the opposite, shrinking pupils down to small pinpoints. Persistent red or bloodshot eyes are common across many substances, and you may notice someone suddenly relying on eye drops or wearing sunglasses indoors.
Weight changes are another strong signal. Stimulants suppress appetite, so unexplained weight loss over weeks or months, sometimes accompanied by nausea, is a red flag. Alcohol and cannabis, on the other hand, can lead to weight gain. Either direction of rapid, unintentional change is worth paying attention to.
Skin and mouth changes vary by substance but tend to be distinctive. Someone snorting drugs may develop a chronically runny nose, nasal congestion, or visible sores around the nostrils. Methamphetamine use causes severe tooth decay and gum disease, sometimes called “meth mouth.” Cannabis smokers may have yellow-stained fingertips and a lingering odor on clothes. Inhalant use can produce a telltale rash around the nose and mouth. Needle marks on the arms or other areas of the body point to injection drug use, though people often try to conceal these with long sleeves.
Behavioral and Social Red Flags
Behavioral changes are often what friends and family notice first, even before physical signs become obvious. One of the hallmark patterns is a loss of interest in activities that used to matter. Hobbies get dropped, social plans get canceled, relationships with longtime friends fade. The person may start spending a great deal of time either obtaining a substance, using it, or recovering from its effects, leaving little room for anything else.
Social withdrawal and secrecy tend to increase as use escalates. Someone who was once open may become evasive about where they’ve been, who they were with, or how they spent their money. Unexplained financial problems are a common downstream effect: money disappearing faster than it should, borrowing frequently, selling possessions, or being unable to cover routine expenses.
You may also notice continued use despite clear consequences. A person keeps drinking even after it’s damaging their marriage. Someone keeps using even after a health scare directly related to the substance. This pattern of choosing the substance over well-being, even when the person recognizes the harm, is one of the core features clinicians use to identify a substance use disorder.
Mood and Personality Shifts
Substance use reshapes how the brain regulates mood, and the effects spill out into daily interactions. Increased irritability, sudden anger over small things, and unpredictable mood swings are common across nearly all substances. A person may seem like a different version of themselves: more hostile, more argumentative, more defensive when questioned.
The specific substance shapes the emotional picture. Someone using opioids may appear sedated, indifferent, or “out of it,” with difficulty keeping their eyes open and a general air of detachment. A person using stimulants may seem unusually energized or agitated, sometimes expressing unusual thoughts or reacting to things others can’t see or hear. During withdrawal from stimulants, the opposite happens: deep fatigue, depressed mood, and an inability to feel pleasure that can last days or weeks. Opioid withdrawal brings intense physical misery (flu-like symptoms, vomiting, insomnia) along with severe anxiety and agitation.
Paranoia and distrust can also emerge, particularly with stimulant use. A person may become suspicious of others without clear reason, perceive personal attacks that aren’t there, or react with hostility to mild criticism.
Problems at Work or School
Performance decline is one of the most measurable signs. Repeated absences, chronic tardiness, missed deadlines, and a noticeable drop in the quality of work all point to something pulling a person’s focus and energy away. The pattern typically worsens over time. Early on, the person may still be able to compensate, but as substance use progresses, the ability to meet basic obligations at work, school, or home breaks down. Failure to fulfill major responsibilities in these settings is one of the eleven diagnostic criteria clinicians use to assess substance use disorders.
Objects and Environmental Clues
Sometimes the evidence is physical. Paraphernalia varies by substance, but common items include small glass pipes, rolling papers, tin foil with burn marks, small spoons, needles, or cut-up straws and pen casings used for snorting. Empty aerosol cans, tubes of glue, or rags with chemical odors suggest inhalant use. For marijuana, look for grinders, roach clips, bongs, or e-cigarettes being used for concentrates rather than standard vaping liquid.
Less obvious items can also be telling. Excessive use of breath fresheners, mouthwash, or oral sprays may be an attempt to mask the smell of smoke or alcohol. Empty lipstick casings, hollowed-out markers, candy wrappers, and small plastic baggies are occasionally used to carry or hide drugs. Pacifiers or lollipops in an adult’s possession can indicate MDMA use, as the drug causes intense teeth grinding.
How Many Signs Add Up to a Problem
Clinicians diagnose substance use disorders on a spectrum based on eleven criteria. These include taking more of a substance than intended, unsuccessful attempts to cut back, spending excessive time obtaining or recovering from a substance, intense cravings, neglecting responsibilities, continuing use despite relationship problems, giving up important activities, using in physically dangerous situations, using despite known health consequences, needing increasing amounts for the same effect (tolerance), and experiencing withdrawal symptoms when stopping.
Meeting two or three of these criteria indicates a mild disorder. Four or five points to moderate. Six or more is considered severe. You don’t need to formally diagnose anyone, but this framework helps you gauge whether a pattern of behavior has crossed from occasional use into something more concerning. The more criteria you can identify, the more urgent the situation.
A Simple Self-Check for Alcohol
If you’re wondering about someone’s drinking specifically, a widely used screening tool called the CAGE questionnaire asks just four questions. Has the person ever felt they should cut down? Have others annoyed them by criticizing their drinking? Have they ever felt guilty about it? Have they ever needed a drink first thing in the morning to steady their nerves or shake off a hangover? “Yes” to two or more of these questions is a strong indicator of a drinking problem. The questions work well as a quiet personal assessment, and they apply whether you’re evaluating someone else’s behavior or honestly examining your own.
How to Raise the Subject
Recognizing the signs is only useful if it leads somewhere. If you’re concerned about someone, a direct, honest conversation is often the most effective starting point. Approach the person privately, not when they’re under the influence. Focus on specific behaviors you’ve observed and how those behaviors have affected you and others, rather than labeling the person or making broad accusations.
If a one-on-one conversation doesn’t lead to change, a more structured approach called an intervention brings together people who care about the individual to collectively describe the impact of the addiction and present a clear treatment plan. Each participant shares specific examples of destructive behavior and its consequences. The goal is to offer a concrete path forward with defined steps, not to shame or punish. If someone important to the process might create conflict in the room, having that person contribute a written letter instead can keep the conversation productive.
The key throughout is specificity. Vague concern is easy to dismiss. Concrete observations, named patterns, and a ready treatment option are much harder to wave away.