Wearing-off is when Parkinson's symptoms begin to reappear or become noticeably worse before it is time to take the next scheduled dose of medication. As wearing- off becomes more obvious, it may be harder to control the time when levodopa results in a good response ("on" time) and the time when there is a poor response to levodopa ("off" time).

It is important to be aware of the changes in symptoms that may indicate wearing-off. In this way, it may be possible to adjust therapy to provide better control of symptoms. As these changes take place, other unwanted drug-induced effects may also occur. These include involuntary movements such as dyskinesia (twisting, turning movements) or dystonia (abnormal positions and postures).