How to tell if someone is on drugs: Signs by substance

Knowing the signs of drug use can help you identify when someone you care about may need help. Different substances produce different observable effects, and understanding these distinctions can help you have more informed, specific conversations. One important caveat: none of these signs alone confirms drug use. Many have medical explanations. Look for clusters of changes — multiple signs occurring together, especially when accompanied by behavioral changes.

Opioids (heroin, fentanyl, prescription painkillers)

Observable signs include pinpoint (constricted) pupils even in dim lighting, drowsiness or nodding off at inappropriate times (the characteristic "nod"), slowed or shallow breathing, slurred speech, itching or scratching (particularly the nose and face), constipation complaints, and small burn marks on fingers or lips (from smoking). Behavioral changes include social withdrawal, loss of interest in activities, missing money or valuables, finding aluminum foil, small bags, or syringes, and unexplained absences.

Stimulants (cocaine, methamphetamine, Adderall)

Observable signs include dilated pupils, rapid speech and heightened energy followed by crashes, decreased appetite and weight loss, jaw clenching or teeth grinding, restlessness and inability to sit still, sweating, and in chronic meth use, skin picking (leading to sores) and dental deterioration. Behavioral changes include staying awake for extended periods followed by prolonged sleeping, increased talkativeness and grandiosity, paranoia, irritability, and financial problems.

Cannabis

Observable signs include red or bloodshot eyes, distinct sweet or skunky odor on clothes or breath, increased appetite (especially for snacks), slower reaction times, and dry mouth. Behavioral changes include decreased motivation, memory lapses, giggling inappropriately, and changes in friend groups.

Alcohol

Observable signs include smell of alcohol on breath (or attempts to mask it with mouthwash or gum), slurred speech, unsteady gait, facial flushing, and tremors in the morning (a sign of dependence). Behavioral signs include drinking alone, hiding bottles or containers, personality changes when drinking, blackouts, and increased tolerance (needing more to achieve effects).

Benzodiazepines (Xanax, Valium, Klonopin)

Observable signs include drowsiness and sedation, confusion or disorientation, slurred speech, impaired coordination similar to alcohol intoxication, and memory problems. These signs can be particularly hard to distinguish from alcohol intoxication.

What to do if you recognize these signs

Approach the conversation with compassion, not accusation. Express specific observations: "I've noticed you seem very tired lately and you've missed several days of work" rather than "I think you're on drugs." Offer help rather than ultimatums (at least initially). Learn about treatment options so you can present them when the person is ready. Read our guide on how to get someone into treatment.

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Authoritative sources

This article references guidelines from: SAMHSA · NIDA

Frequently asked questions

Disclaimer: Informational only. Not medical advice. SAMHSA: 1-800-662-4357.