Context:Patients with adrenal insufficiency (AI) (primary AI [PAI], secondary AI due to a pituitary disorder [PIT] and congenital adrenal hyperplasia [CAH]) have reduced life expectancy; however, the underlying explanation remains unknown.Objective:To evaluate characteristics, comorbidities, and hospitalizations in AI patients.Design:Retrospective observational.Setting and Population:Using a United States-based national payer database comprising of more than 108 million members, strict inclusion criteria including diagnostic codes and steroid prescription records were used to identify 10 383 adults with AI; 1014 with PAI, 8818 with PIT, and 551 with CAH. Patients were matched 1:1 to controls, based on age (±5 y), gender, insurance, and region and followed for more than 12 months.Intervention:None.Main Outcome Measures:Demographic variables, comorbidities (diabetes mellitus [DM] types 1 and 2, depression, anxiety, hyperlipidemia, hypertension) and hospitalization incidence.Results:Compared with controls, patients with AI had higher odds of DM, hypertension, hyperlipidaemia, depression, and anxiety, ranging from an odds ratio (OR) of 1.51 for hyperlipidaemia in PAI to 3.85 for DM in CAH. Odds of having DM (OR, 3.85; 95% confidence interval, 2.52–5.90) or anxiety (OR, 2.99; 95% confidence interval, 2.02–4.42) compared with controls were highest in CAH, whereas depression was highest in PAI and PIT (OR, 2.40 and 2.55). ORs of hyperlipidaemia and hypertension (OR, 1.98 and 2.24) were highest in the PIT cohort. Inpatient admissions were more frequent in PAI (4.64:1; P < .0001) and PIT (4.00:1; P < .0001) than controls; infection was the most common cause for admission.Conclusion:Patients with AI carry a significant metabolic and psychiatric burden, with higher risk of comorbidities and hospital admissions than matched controls.