Patients should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications. Of particular concern to individuals taking insulin are:

• Alcohol. Patients should ask their physician for guidelines about how much is safe to drink, as alcohol increases glucose (blood sugar). Usually, smaller amounts of alcohol do not cause problems. But larger amounts taken in a single sitting or over long periods of time (especially without food) can enhance insulin’s effect in lowering glucose levels and keeping them low for longer periods of time.
  
  
• Beta blockers. These common blood pressure drugs (antihypertensives) can increase the likelihood of both high glucose levels (hyperglycemia) and low glucose levels (hypoglycemia). In addition, these medications sometimes mask symptoms of hypoglycemia, such as rapid heartbeat. They can also keep glucose levels low for longer periods of time. Other antihypertensives that may interact with insulin include ACE inhibitors and diuretics.
  
  
• Corticosteroids. These drugs often increase glucose levels. As a result, insulin dosages may have to be increased during corticosteroid treatments and for a while after treatment is completed.
  
  
• Pentamidine. This antiprotozoal pneumonia drug may cause the pancreas to release insulin too quickly. This causes blood glucose to first drop too low, then to become too high.
  
  
• Aspirin. Using aspirin can increase the action of insulin and may cause hypoglycemia.
  
  
• Oral contraceptives. Birth control pills may decrease the effect of insulin.

Other medications that may interact with insulin include some antidiabetic agents, diet pills, MAO inhibitors (class of antidepressants), niacin (a cholesterol-reducing drug), sulfa antibiotics, thyroid drugs, tranquilizers and anabolic steroids.

In addition, people who smoke or have quit smoking within the past six months should not use inhaled insulin, according to the U.S. Food and Drug Administration (FDA).