[MW Giles]

As a powerful stimulant, methamphetamine, even in small doses, can increase wakefulness and physical activity and decrease appetite. Methamphetamine can also cause a variety of cardiovascular problems, including rapid heart rate, irregular heartbeat, and increased blood pressure. Hyperthermia (elevated body temperature) and convulsions may occur with methamphetamine overdose, and if not treated immediately, can result in death.

The exact mechanisms whereby drugs like methamphetamine produce euphoria (the pleasurable high) are still poorly understood. But along with euphoria, methamphetamine use releases very high levels of the neurotransmitter dopamine in the reward circuit, which "teaches" the brain to repeat the pleasurable activity of taking the drug. Dopamine is involved in motivation and motor function and its release in the reward circuit is a defining feature of addictive drugs. The elevated release of dopamine produced by methamphetamine is also thought to contribute to the drug's deleterious effects on nerve terminals in the brain.


How long the effects last depends on so many things:
- what dose you take
- how soon you repeat the dose (has the first one worn off before you take the second)
- total intake before you stop
- have you taken it regularly before
- what other things you take with it
- general fitness
- body mass
- activity levels while affected
etc etc

If you were tired and took a reasonable dose, say towards midnight, then you would probably still be getting the benefit six or perhaps eight hours later. Some sources say you can see effects 12-14 hours after taking and even 24 hours later, but that does not account for taking several hits in a day

None of that was personal experience

Martin