The effects of methamphetamine differ depending on:

• the form of the substance (pharmaceutical or street; pills, powder, or crystal)
• the method of use (swallowed, snorted, injected, or smoked)
• the amount used (small or larger dose)

When the crystal form of methamphetamine is smoked or injected, it produces an immediate rush. When any form of methamphetamine is snorted or swallowed, it may take up to 20 minutes to take effect. Most often the feelings of pleasure that follow last for 4 to 12 hours, but some people stay high for longer.

A low dose of methamphetamine may produce the following effects: increase in energy, raised heart rate and blood pressure, increased respiration, and reduced appetite and thirst. Low dose use may also create feelings of euphoria, alertness, self confidence, heightened libido, restlessness, anxiousness and aggression. It is difficult to define “low dose” because it depends on the user’s metabolism as well as the concentration of the drug – and that is impossible to know when it is bought illegally.

The effects often diminish and change with high dose and frequent use. Effects may include: teeth grinding/clenching, agitation, restlessness, decrease in libido, and inability to focus. Other negative effects include mild to severe tremors and athetosis (writhing, jerky, or flailing movements), hostility, and paranoia. Sometimes users believe they have bugs under their skin and constantly scratch or pick at their arms and legs. Or they hear and see things that aren’t really there. Over time, methamphetamine use may also cause sleep problems, tooth and gum disease (called “meth mouth”), and organ damage. Users may also develop serious mental health problems.

Because using crystal meth can feel good at first, some people use the drug again and again. But after a short time, they begin to need more of the drug in order to feel its effects. This is called “tolerance.” Tolerance develops because the brain tries to rebalance itself by limiting the impact of the drug on the brain. As a result, the person may begin to feel tired, agitated, aggressive, and depressed. And they may need to take the drug regularly just to feel normal. This condition is called “dependence.”

There is potential for overdose. A person who uses a large amount of meth without building up tolerance can experience convulsions, a stroke or heart attack.