If you take medication, work out when it actually comes on and when it fades, then put the demanding work inside that window. Spending your best hours on email is a waste of something limited.

What the research says

A study of 124 adults with ADHD doing twelve weeks of a manualised programme compared those also taking medication with those who were not, across core symptoms, emotional symptoms, self esteem and functioning. It treats medication and structured skills work as things that sit alongside each other, which is the assumption behind planning a day around a dose. The timing question itself was not tested, so this stays sensible practice rather than a finding.

Strength of evidence: one line of research. A single study, or a theoretical account.