Emerging research has identified metabolic pathways that are crucial for the proper regulation of immune cells and how, when deranged, they can cause immune dysfunction and disease progression. However, due to technical limitations such insights have relied heavily on bulk measurements in immune cells, often activated in vitro. But with the emergence of single-cell applications, researchers can now estimate the metabolic state of individual immune cells in clinical samples. Here, we review these single-cell techniques and their ability to validate common principles in immunometabolism, while also revealing context-dependent metabolic heterogeneity within the immune cell compartment. We also discuss current gaps and limitations, as well as identify future opportunities to move the field forward toward the development of therapeutic targets and improved diagnostic capabilities.