Most medicines are taken with breakfast which is usually unproblematic and has the advantage of improving adherence through establishment of a daily routine. However, due to alterations in absorption from the gastrointestinal tract, there are a number of medicines that either lose (such as bisphosphonates) or gain (such as albendazole) efficacy if taken together with food. Food components can also affect drug-metabolising enzymes and even cause drug toxicity (alcohol and grapefruit juice are notable examples). Conversely, drugs such as monoamine oxidase inhibitors can inhibit the metabolism of tyramine in tyramine-rich foods and lead to adverse circulatory reactions. These and other examples of when the ingestion of medication together with food can cause clinically relevant problems are discussed in this article.