Summarize:

There are an array of symptoms that might point to a person being on drugs, because it will depend upon the drug and its properties. For some, drugs will make them drowsy, relaxed, and happy. Other people who abuse substances tend to be very energetic and erratic in their behavior. You may notice that the person is always on the move but never seems to actually achieve anything. Other behaviors to look out for include: Acting irrationally or rashly, without thinking about the consequences. Having trouble concentrating. The person may also have a very short attention span and does not stick to projects for long. Forgetting important meetings and events. Many substance abusers tend to gravitate towards risky or treacherous activities. This is because, it part, they do not consider the consequences of their actions. Because of their poor judgement, they may: Make faulty decisions. Indulge in detrimental behaviors that may be harmful to themselves or others. Have a lot of legal issues. Always be out of money. Someone who is abusing substances may have a track record of breaking things and mismanaging items around the office. You may also notice that the person loses things a lot, or is always asking to borrow other people's things because they broke or lost their own items. A person who is abusing drugs may develop a nervous attitude when they get to work. The person may speak quickly but without really thinking about what they are saying. On the flip side, the person may also talk very confidently about something that they actually know very little about. A substance abuser may miss work often, either because they are abusing drugs or are trying to hide the fact that they are high. Their excuses may be weak or lack any backing.
Watch out for unusual behavior. Watch out for a person who does risky activities. Take note if someone has a bad track record of destroying property. Keep track of nervous or confused behaviors. Keep track of how often the suspected person misses work.