Long-term use of crystal meth may result in addiction. Crystal meth abuse can also cause violent behavior, anxiety, and insomnia, as well as psychotic behavior such as paranoia, hallucinations, mood swings, and delusions. The crystal meth user can also develop a tolerance to the drug, which requires the user to take increasing amounts to induce the desired effects. Chronic users of crystal meth are also characterized as having poor hygiene, a gaunt or pale complexion, and, at times, sores on their bodies from scratching at "crank bugs", which is a common delusion that bugs are crawling under their skin. Additionally, long-term use of crystal meth can cause damage to the dopamine-producing cells of the brain.

Crystal meth use produces increases in energy and alertness and a decrease in appetite. An intense rush is felt, almost instantaneously, when a user smokes or injects methamphetamine. Snorting methamphetamine affects the user in approximately 5 minutes, whereas orally ingesting methamphetamine takes about 20 minutes for the user to feel the effects. The intense rush and high felt from crystal meth results from the release of high levels of dopamine into the section of the brain that controls the feeling of pleasure. The effects of crystal meth can last up to 12 hours. Side effects of crystal meth use are convulsions, dangerously high body temperature, stroke, cardiac arrhythmia, stomach cramps, and shaking.

Methamphetamine is a Schedule II narcotic under the Controlled Substances Act, Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970. If a person is convicted of trafficking methamphetamine, depending on the amount of methamphetamine and if a person was injured or killed during the crime, the trafficker can receive 5 to 20 years in prison and a fine not to exceed $10 million for the first offense. In addition to being a Schedule II drug itself, methamphetamine is made from chemicals that are regulated under the Comprehensive Methamphetamine Control Act of 1996. This act broadens controls on drugs such as ephedrine and pseudoephedrine, which are used in the manufacturing of methamphetamine. It also increases penalties for trafficking and possession of such chemicals without registration.