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Symptoms and Signs of Insulin Reaction

Doctor's Notes on Insulin Reaction

An insulin reaction occurs when a person with diabetes becomes confused or unconscious due to low blood sugar (hypoglycemia) caused by insulin or oral diabetic medications. In people with diabetes, the pancreas is unable to produce enough insulin to meet the body's demand and treatment may include oral hypoglycemics, insulin, or both. A common cause of an insulin reaction (or hypoglycemia) is a missed meal. Other causes for insulin reaction include exercise and medication error.

Mild symptoms of insulin reaction include dizziness, irritability, hunger, shakiness, sweating, and rapid heartbeat. Moderate symptoms of insulin reaction include confusion, headache, and poor coordination. Severe symptoms of insulin reaction include unconsciousness, seizures, coma, stroke-like symptoms, and hypothermia (low body temperature) if the hypoglycemia persists for a prolonged period of time.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/21/2019

Insulin Reaction Symptoms

The symptoms of an insulin reaction are due to decreased brain cell function because of lack of glucose within the bloodstream. The longer the hypoglycemia persists, the more severe the symptoms.

Mild Symptoms of Insulin Reaction

Moderate Symptoms of Insulin Reaction

Severe Symptoms of Insulin Reaction

  • unconsciousness
  • seizures
  • coma
  • stroke like symptoms
  • hypothermia (low body temperature) may occur if the hypoglycemia persists for a prolonged period of time

Insulin Reaction Causes

Insulin reactions occur when there is an imbalance of food intake and the amount of insulin in the body. Oral hypoglycemic medications can remain active in the body for more than 24 hours. The effects of Injectable insulin can be short or very long depending upon the type. Even in individuals whose diabetes is well controlled and regulated with medication, a variety of factors can cause the insulin/glucose levels to fluctuate from the normal range. Also, alcohol plays a role in causing hypoglycemia?

People who have had diabetes for 10-20 years and/or have been on long term or large doses of insulin are more prone to "insulin unawareness". They can suddenly become hypoglycemic without any warning and should check sugar before driving. They should consider Continuous Glucose Monitoring or a handheld reader with a 14-day patch that lets them read blood sugar at any time.

Perhaps the most common cause of an insulin reaction or hypoglycemia is a missed meal. Once insulin is injected or a diabetes medication is taken, its effect needs to be balanced by caloric intake from food (providing glucose to bind with the insulin). If the number of calories eaten decreases, blood glucose levels drop and the insulin acts unopposed, which causes the characteristic symptoms of an insulin reaction. An insulin reaction can also occur with exercise. When a person exercises the muscle cells need extra energy (glucose), and if food intake is decreased, the blood sugar levels will drop.

Another common cause of insulin reaction is medication error. If a person with diabetes injects too much insulin or takes too many diabetic drugs, the insulin levels in the blood rise because there is not enough glucose in the blood to bind to the insulin, and an insulin reaction occurs.

Disorders of these endocrine glands can also affect the balance between insulin and glucose in the body.

Type 2 Diabetes Diagnosis, Treatment, Medication Slideshow

Type 2 Diabetes Diagnosis, Treatment, Medication Slideshow

Type 2 diabetes can affect all people, regardless of age. Early symptoms of type 2 diabetes may be missed, so those affected may not even know they have the condition. An estimated one out of every three people within the early stages of type 2 diabetes are not aware they have it.

Diabetes interferes with the body's ability to metabolize carbohydrates for energy, leading to high levels of blood sugar. These chronically high blood sugar levels increase a person's risk of developing serious health problems.

Potential Consequences of High Blood Sugar

  • Nerve problems
  • Vision loss
  • Joint deformities
  • Cardiovascular disease
  • Diabetic coma (life-threatening)
  • Other diabetes complications from high blood pressure are listed further along in this slideshow


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.