Stress

• A patient's glucose levels may increase due to severely stressful events such as trauma, a stroke or a heart attack, according to the U.S. National Library of Medicine.
  
  

Drugs

• Glucose levels can increase when a patient takes drugs such as diuretics, corticosteroids and estrogens. Tricyclic antidepressants, lithium and salicylates can also raise glucose levels.
  
  

Food

• People can have high blood glucose levels when they consume too much food.
  
  

Insulin

• Individuals with insufficiently low levels of insulin can develop high levels of glucose.
  
  

Diseases

• Patients with hyperthyroidism, pancreatitis and pancreatic cancer can develop high blood glucose levels in addition to people with diabetes. Individuals with Cushing's syndrome, acromegaly or pheochromocytoma may have increased blood levels of glucose.