Cachexia is a systemic wasting syndrome prevalent in patients with cancer that significantly affects quality of life, health care costs, and therapeutic outcomes. Despite its clinical importance, cachexia is rarely formally diagnosed. This deficiency presents a challenge for effective patient management and care, health care resource allocation, and the advancement of therapeutic approaches. Here, we highlight impedances to the diagnosis and coding of cachexia, including the absence of standardized therapy, a lack of incentives for accurate coding, and overlapping clinical features with other conditions. We differentiate cachexia from related conditions like unintentional weight loss, sarcopenia, frailty, and protein-calorie malnutrition, outlining their distinct clinical features and inter-relations. We propose an approach to enhance diagnostic accuracy and coding for cachexia. This effort will enable better prevalence data, translation of mechanism-based therapy development, patient identification and stratification, and ultimately advanced diagnostics and US Food and Drug Administration-approved treatments for cachexia.