The hippocampus plays an important role in human memory and is known to be vulnerable to extreme hyperglycemia and hypoglycemia in animal models of type 1 diabetes. Within humans with type 1 diabetes, exposure to glycemic extremes has been associated with alterations in hippocampal structure and in memory function, but results are inconsistent. It has been hypothesized that the effects of hypoglycemia and hyperglycemia on the hippocampus may depend on when during neurodevelopment these extremes occur, possibly explaining some of these inconsistencies. However, data addressing this concept are limited. We review here the existing literature on this complex topic and suggest future avenues of required research.