BACKGROUND: Intranasal insulin is a potential treatment for neurodegenerative disease shown to increase cerebral glucose uptake, reduce amyloid plaques, and improve verbal memory in cognitively impaired as well as healthy adults. Investigations have suggested rapid-acting insulins such as glulisine may result in superior cognitive benefits compared with regular insulin. OBJECTIVE: The aim of this study was to evaluate the safety and efficacy of rapid-acting intranasal glulisine in subjects with amnestic mild cognitive impairment (MCI) or mild probable Alzheimer's disease (AD). METHODS: We performed a single-center, randomized, double-blind, placebo-controlled study to evaluate the efficacy of intranasal glulisine 20 IU twice daily versus saline placebo in 35 memory-impaired (MCI/AD) subjects using the Impel NeuroPharma I109 Precision Olfactory Delivery (POD(®)) device. The 13-item Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog13), Clinical Dementia Rating (CDR) global score, and Functional Assessment Questionnaire (FAQ) were measured at baseline and 3 and 6 months. Secondary outcome measures included digit span forward/backwards, Trail Making Test Parts A/B, Controlled Oral Word Association Test (COWAT), and Weschler Memory Scale (WMS)-IV logical memory. Adverse effects (AEs) and serious adverse effects (SAEs) were measured along with blood glucose/insulin levels. RESULTS: No significant difference in ADAS-Cog13, CDR Sum of Boxes (CDR-SOB), or FAQ scores were found between treatment groups at 3 and 6 months. Subjects in the saline group were significantly older than those in the glulisine group (p = 0.022). No significant differences in sex, education, apolipoprotein E4 (ApoE4) status, and Montreal Cognitive Assessment (MoCA) score existed between treatment groups. Overall, the number of adverse events per person was similar between groups (2.32 vs. 2.24; p = 0.824), although subjects receiving intranasal glulisine had higher rates of nasal irritation (25.0% vs. 13.9%) and respiratory symptoms (15.9% vs. 8.3%) compared with placebo. There were no differences in blood sugar or rate of hypoglycemia between the treatment and placebo groups. CONCLUSIONS: Intranasal glulisine was relatively safe and well-tolerated and did not consistently impact peripheral glucose or insulin levels. There were no enhancing effects of intranasal glulisine on cognition, function, or mood, but the ability to detect significance was limited by the number of subjects successfully enrolled and the study duration. CLINICALTRIALS. GOV REGISTRATION: NCT02503501.