I’m a nurse. We usually recommend at least 350 calories, but ideally with a meal, but it also depends on the medication. For some, it’s to slow how quickly the medication is absorbed and/or reduce side effects, and isn’t necessary for the medication to work (e.g., stimulants, some antidepressants). For others, taking with food is necessary for the medication to be absorbed effectively so that it works (e.g., Latuda, used to treat mood and psychotic disorders).