jats:pHyperglycemia is due to a dysregulation in the complex mechanisms implicated in glucose homeostasis. Chronic hyperglycemia, as measured by hemoglobin A1c (HbA1c), is a key risk factor for the development of microvascular and macrovascular complications, which in turn negatively influence the prognosis of patients with diabetes. Several studies have shown that acute hyperglycemia can add to the effect of chronic hyperglycemia in inducing tissue damage. Acute hyperglycemia can manifest as high fasting plasma glucose (FPG) or high postprandial plasma glucose (PPG) and can activate the same metabolic and hemodynamic pathways as chronic hyperglycemia. Glucose variability, as expressed by the intraday glucose fluctuations from peaks to nadirs, is another important parameter, which has emerged as an HbA1c-independent risk factor for the development of vascular complications, mainly in the context of type 2 diabetes. Treatments able to decrease HbA1c have been associated with positive effects in terms of reducing risk for the development and progression of complications. Further studies are required to clarify the impact of strategies more specifically targeting components of acute hyperglycemia, to improve outcomes in patients with diabetes.</jats:p>