Many factors can alter glucose (blood sugar) levels in people with diabetes. Common triggers of high blood glucose (hyperglycemia) include:

• Skipping or taking too little insulin or oral diabetes medication (antidiabetic agents), taking insulin or antidiabetic agents at the wrong time, or using expired or spoiled insulin.
  
  
• Malfunction of an insulin pump, such as an obstruction in tubing.

• Increased emotional stress.
  
  
• Illness, infection or other physical stress.
  
  
• Lack of exercise.
  
  
• Overeating or eating the wrong type of food.
  
  
• Dawn phenomenon and the Somogyi effect (rebound hyperglycemia in the morning after an overnight bout of hypoglycemia).
  
  
• Certain medications, such as corticosteroids (an anti-inflammatory class of immunosuppressives), diuretics, beta blockers (a class of antihypertensives), antipsychotics, some antidepressants and certain antibiotics.

In some cases nondiabetics can experience hyperglycemia due to causes such as medications, intravenous glucose, severe stress (e.g., from a heart attack or stroke), eating disorders, pancreatitis, pancreatic cancer, polycystic ovarian syndrome, Cushing's disease (overactive adrenal glands) or acromegaly (overactive pituitary gland). Where such factors are chronic, secondary diabetes may result.