Cinnamon is a spice that has been used in various cultures for centuries for its potential health benefits. While there are health claims for a variety of health conditions, it has continuously been explored for its ability to improve glucose handling in diabetes. Cinnamon is a very popular supplement used by patients with diabetes to help normalize blood glucose levels. A systematic review of the literature was conducted to assess the available evidence evaluating effects on diabetes and glucose handling with the use of various species of cinnamon. The intention was to summarize the existing evidence for cinnamon's effects on blood glucose, both for safety and efficacy, to help guide providers and consumers alike. Reviewing the available literature for the different types of cinnamon and their effects on the diabetes disease process, there are multiple proposed mechanisms for how cinnamon could improve diabetes, including increasing insulin sensitivity by multiple receptor signaling pathways, reducing inflammation, enhancing glucose uptake by effects on glucose transporter proteins, and effects on gastric emptying, and blocking glucose absorption. There appears to be conflicting evidence on whether cinnamon produces any significant effect on glucose parameters, and the extent of these effects. There are several variables that could explain these conflicting data, such as patient sample size, doses and formulations of cinnamon used, baseline patient characteristics, and study duration. A more in-depth evaluation and rating of the available evidence could help clarify this, but data suggest that in some circumstances, cinnamon may have modest effects on improving glucose handling in adults. The safety profile also has been demonstrated to be extremely favorable, with very few adverse events reported in the active treatment groups across all studies. Based upon these data, clinicians should consider cinnamon to be a potential adjunctive therapy to traditional diabetes treatments, and should be open to discussing this with patients expressing interest in the supplement.