A long-established approach to the pharmacological treatment of disease has been to start low and go slow. However, clinicians often prescribe up to maximum tolerated dose (MTD), especially when treating acute and more severe disease, without evidence to show that MTD is more likely to improve outcomes. Cardiovascular guidelines for some indications advocate MTD even in prevention, for example hypercholesterolaemia, without compelling evidence of better outcomes. This review explores the origins and potential problems of prescribing medications at MTD. Oral effective dose 50 (ED50) may be a useful guide for balancing efficacy and safety.