Why do some people feel more tired or low-energy on ADHD medication instead of more focused?

Mine turned out to be the appetite thing, wasn't eating lunch most days without realizing it because I just... forgot, once I started forcing a proper lunch the 2pm fog mostly went away. Worth ruling that out before assuming it's the medication itself.

Could genuinely be either, and the honest answer is it's worth flagging to your provider rather than guessing, but there are a few common, non-alarming explanations worth knowing about first. Some people do get an initial paradoxical tired/foggy response in the first days to weeks of starting a stimulant, especially if the dose is on the higher end of a starting range for their body, this often settles as your system adjusts. Another common cause: stimulants can suppress appetite, and if you're eating less or eating later in the day than usual without noticing, that alone can produce a foggy, low-energy feeling that gets misattributed entirely to the medication itself rather than to skipped meals or dehydration. Sleep is the other big variable, some ADHD medications can affect sleep quality or timing even if you don't consciously notice trouble falling asleep, and a few nights of subtly worse sleep compounds into exactly the kind of afternoon fog you're describing. If it's persistent past the first couple weeks and not explained by eating or sleep changes, that's a real signal for your provider that the dose, timing, or even the specific medication might not be the right fit for you, tired instead of focused isn't the expected response and isn't something you should just push through indefinitely.