Chronic users develop a tolerance and dose levels may escalate. This appears to be particularly true of methamfetamine.
[patient.info]
Typical Overdose Symptoms to Look for When people consistently take amphetamines for a long time, they typically develop a tolerance to the drug, which, in turn, results in
[projectknow.com]
However, patients who chronically abuse amphetamines develop tolerance.
[brainprotips.com]