Nicotinamide adenine dinucleotide (NAD⁺) is a ubiquitous metabolite that serves an essential role in the catabolism of nutrients. Recently, there has been a surge of interest in NAD⁺ biology, with the recognition that NAD⁺ influences many biological processes beyond metabolism, including transcription, signalling and cell survival. There are a multitude of pathways involved in the synthesis and breakdown of NAD⁺, and alterations in NAD⁺ homeostasis have emerged as a common feature of a range of disease states. Here, we provide an overview of NAD⁺ metabolism and summarise progress on the development of NAD⁺-related therapeutics.