Methamphetamine comes in many forms and can be smoked, snorted, orally ingested, or injected. The drug alters moods in different ways, depending on how it is taken. Immediately after smoking the drug or injecting it intravenously, the user experiences an intense rush or "swap" that lasts only a few minutes and is described as extremely pleasurable. Snorting or oral ingestion produces euphoria -- a high but not an intense rush. Snorting produces effects within 3 to 5 minutes, and oral ingestion produces effects within 15 to 20 minutes.

As with similar stimulants, methamphetamine most often is used in a "binge and crash" pattern. Because tolerance for methamphetamine occurs within minutes -- meaning that the pleasurable effects disappear even before the drug concentration in the blood falls significantly -- users try to maintain the high by binging on the drug.

In the 1980's, "ice," a smokable form of methamphetamine, came into use. Ice is a large, usually clear crystal of high purity that is smoked in a glass pipe like crack cocaine. The smoke is odorless, leaves a residue that can be resmoked, and produces effects that may continue for 12 hours or more.

A tweaker is a meth abuser who probably has not slept in 3-15 days and is irritable and paranoid. Tweakers are considered the most dangerous type of meth abuser to medical personnels, and law enforcement officers. Tweakers often behave or react violently and if a tweaker is using alcohol or another depressant, his negative feelings and associated dangers intensify. The tweaker craves more meth, but no dosage will help re-create the euphoric high, which causes frustration, and leads to unpredictably and potential for violence. To an outside observer a tweaker can appear normal. Their eyes can be clear, speech concise, and movements brisk. However, a closer look will reveal that their eyes are moving ten times faster than normal, their voice has a slight quiver, and their movements are quick and jerky. These physical signs are more difficult to identify if the tweaker is using a depressant. Tweakers are often involved in domestic disputes and motor vehicle accidents. They may also be present at "raves" or parties and they may participate in spur-of-the-moment crimes, such as purse snatchings or assaults, to support their habit.

1. When in the presence of a tweaker keep a 7-10 ft. distance. Coming too close can be perceived as threatening.
2. Do not shine bright lights at him. The tweaker is already paranoid and if blinded by a bright light he is likely to run or become violent.
3. When communicating with a tweaker slow your speech and lower the pitch of your voice. A tweaker already hears sounds at a fast pace and in a high pitch.
4. Slow your movements. This will decrease the odds that the tweaker will misinterpret your physical actions. It is important it keep your hands visible. If you place your hands where the tweaker cannot see them, he might feel threatened and could become violent.
5. Do your best to keep the tweaker talking. A tweaker who falls silent can be extremely dangerous. Silence often means that his paranoid thoughts have taken over reality, and anyone present can become part of the tweaker's paranoid delusions.

• Often crystal meth users will have jumpy eyes. This term describes how a user's eyes will tend to jump around and flit from side to side.
• Many times crystal meth users have a loss of interest in normal activities, food, water, sex, sleep.
• Crystal meth users will do what is referred to as "Tweaking" or "Geeking". What these terms mean is to do something for hours on end over and over again. For example a girl fixing her hair for 7 hours; or walking around a shopping store for 9 hours.
• Sketched out is a term used to describe agitated, nervous, moody, irritable, and aggressive behavior.
• Often crystal meth users experience severe symptoms of sleep deprivation: hallucinations, delusions, extreme paranoia, violent outbursts.
• Many times tweakers may have an unpleasant chemical body odor.
• Crystal meth withdrawal behavior is often characterized by constant jitteriness, listlessness, and/or severe depression.
• Meth users will do stupid things for hours on end without really accomplishing anything.
• Meth users will hallucinate and may have delusional conversations with no one.
• Meth users can become agitated and get into fights over minor things.
• Meth users often commit crimes of opportunity when tweaking.
• Meth users may scratch themselves or pick at JIB sores until they become infected.
• Meth users may smell bad from chemical residue coming out of their pours.
• Meth users may get so paranoid from sleep deprivation that they can be afraid to go out.
• Meth users may crash and wake up in strange places with strange people.
• Meth users may hangout with other people who they wouldn't go near if straight.