Diabetes mellitus (DM) increases the risk of infections due to hyperglycemia, immune dysfunction, and complications like micro- and macroangiopathies. Infections are more frequent and severe in diabetic patients, affecting various organs. Key infections include foot infections, malignant external otitis, rhinocerebral mucormycosis, and gangrenous cholecystitis. Infections may also be the first sign of DM or a trigger for complications like ketoacidosis and hypoglycemia. Vaccination against pneumococcal and influenza is recommended to reduce hospitalizations, deaths, and medical costs. Hyperglycemia impairs immune function, including neutrophil activity, antioxidant systems, and humoral immunity. Complement system dysfunction and reduced cytokine production contribute to increased susceptibility. Inflammatory cytokines are also affected, with lower production of IL-1 and IL-6 in diabetic patients. Glycation of immunoglobulins may impair antibody function, though clinical responses to vaccination remain adequate. Respiratory infections are common in diabetic patients, with Streptococcus pneumoniae and influenza virus being major causes. Diabetic patients are six times more likely to require hospitalization during influenza epidemics. Vaccination against pneumococcal and influenza is recommended by major health organizations. Tuberculosis is more prevalent in diabetic patients, with higher risk of multi-resistant TB and treatment complications. Diabetic patients are also more susceptible to urinary tract infections, with risk factors including poor glycemic control and anatomical abnormalities. Asymptomatic bacteriuria is common but its clinical significance is debated. Gastrointestinal infections are more frequent in diabetic patients due to altered motility and increased risk of infections. Helicobacter pylori infection is associated with diabetes, though the relationship is not fully understood. Oral and esophageal candidiasis are more common in diabetic patients, with Candida being a major pathogen. Foot infections are a major complication of DM, often leading to amputation and mortality. Infections are classified as moderate or severe based on ulcer depth and extent. Necrotizing fasciitis and Fournier's gangrene are severe infections more common in diabetic patients. Invasive external otitis and rhinocerebral mucormycosis are also more prevalent in diabetic individuals. Periodontitis is more common in diabetic patients and worsens glycemic control. Other infections include hepatitis C and HIV, which are more prevalent in diabetic patients. HIV patients are at higher risk of developing diabetes, with insulin resistance being a key factor. In conclusion, infections are more common in diabetic patients due to hyperglycemia and immune dysfunction. Vaccination is crucial for prevention, and further research is needed to understand the mechanisms and improve vaccination coverage.Diabetes mellitus (DM) increases the risk of infections due to hyperglycemia, immune dysfunction, and complications like micro- and macroangiopathies. Infections are more frequent and severe in diabetic patients, affecting various organs. Key infections include foot infections, malignant external otitis, rhinocerebral mucormycosis, and gangrenous cholecystitis. Infections may also be the first sign of DM or a trigger for complications like ketoacidosis and hypoglycemia. Vaccination against pneumococcal and influenza is recommended to reduce hospitalizations, deaths, and medical costs. Hyperglycemia impairs immune function, including neutrophil activity, antioxidant systems, and humoral immunity. Complement system dysfunction and reduced cytokine production contribute to increased susceptibility. Inflammatory cytokines are also affected, with lower production of IL-1 and IL-6 in diabetic patients. Glycation of immunoglobulins may impair antibody function, though clinical responses to vaccination remain adequate. Respiratory infections are common in diabetic patients, with Streptococcus pneumoniae and influenza virus being major causes. Diabetic patients are six times more likely to require hospitalization during influenza epidemics. Vaccination against pneumococcal and influenza is recommended by major health organizations. Tuberculosis is more prevalent in diabetic patients, with higher risk of multi-resistant TB and treatment complications. Diabetic patients are also more susceptible to urinary tract infections, with risk factors including poor glycemic control and anatomical abnormalities. Asymptomatic bacteriuria is common but its clinical significance is debated. Gastrointestinal infections are more frequent in diabetic patients due to altered motility and increased risk of infections. Helicobacter pylori infection is associated with diabetes, though the relationship is not fully understood. Oral and esophageal candidiasis are more common in diabetic patients, with Candida being a major pathogen. Foot infections are a major complication of DM, often leading to amputation and mortality. Infections are classified as moderate or severe based on ulcer depth and extent. Necrotizing fasciitis and Fournier's gangrene are severe infections more common in diabetic patients. Invasive external otitis and rhinocerebral mucormycosis are also more prevalent in diabetic individuals. Periodontitis is more common in diabetic patients and worsens glycemic control. Other infections include hepatitis C and HIV, which are more prevalent in diabetic patients. HIV patients are at higher risk of developing diabetes, with insulin resistance being a key factor. In conclusion, infections are more common in diabetic patients due to hyperglycemia and immune dysfunction. Vaccination is crucial for prevention, and further research is needed to understand the mechanisms and improve vaccination coverage.