Introduction: Alzheimer’s disease (AD) is characterized by a progressive and persistent deterioration of the whole cognitive function, which results in an impaired cortical function. Some years ago, the connection between AD and type 2 diabetes has been studied, resulting in the term type 3 diabetes (T3D). Methods: This is a literature review, a search for articles published in the last 5 years in the Medline and PubMed databases was performed, using the descriptor: Alzheimer disease, diabetes, insulin resistance. Results: For analysis, 12 articles were selected, with 10 literature reviews and 2 original studies. Among those who explored the cellular and molecular relationship between AD and insulin resistance, possible pathogenic mechanisms, the role of insulin in the brain, environmental factors linked to AD and dietary interventions to prevent neurodegeneration. Conclusion: The relation between AD and type 2 diabetes is due several mechanisms such as lipid metabolism, insulin metabolism and agents related to its functioning, like the ApoEε4, C-peptide, the glycogen synthase kinase 3β (GSK-3β) and the amyloid-beta (Aβ). It is suggested that several changes, mainly in insulin metabolism, can impair neurocognitive function and trigger AD. Future studies are needed to analyze the context of T3D and find possible treatments that attenuate the AD progression and promote quality of life for the patients.