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How is reactive hypoglycemia diagnosed?

Medically reviewed by Carmen Pope, BPharm. Last updated on Oct 30, 2023.

Official answer


Reactive hypoglycemia can be diagnosed by measuring the amount of glucose in a person's blood while they're having symptoms as well as by observing if their symptoms resolve once they eat and their blood glucose levels return to normal.

If the person’s results show a blood glucose level below 70 milligrams per deciliter (mg/dL) while they are having symptoms, a healthcare provider may order a mixed meal tolerance test (MMTT). For this test, a person drinks a high-calorie beverage that contains protein, carbohydrates, and fat such as Ensure or Boost.

Before taking the MMTT and every 30 minutes for five hours, your healthcare provider will test blood glucose levels as well as insulin, proinsulin (an insulin precursor), and another substance produced by the pancreas alongside insulin.

What is reactive hypoglycemia?

Reactive hypoglycemia is when blood glucose (blood sugar) levels drop within four hours of eating or when fasting and is not related to diabetes. Rarely, blood sugar levels may drop randomly unrelated to food intake or deprivation. Reactive hypoglycemia may also be called postprandial hypoglycemia.

What causes reactive hypoglycemia?

Usually, no cause is found, but reactive hypoglycemia is more common in some medical conditions such as noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS), gastric bypass surgery, tumors, ulcer treatment, metabolic disorders, and insulin autoimmune hypoglycemia. It is more common in people who are overweight.

It may occur in some people after a carbohydrate-heavy meal. In many cases, it appears the body continues to release extra insulin even after a meal has been digested. This added insulin makes your blood glucose level drop below normal.

Related questions

What are the symptoms of reactive hypoglycemia?

Symptoms usually start within 4 hours of a meal, or when a person has been fasting for some time and may include:

  • Anxiety
  • Blurred vision
  • Rapid heart rate
  • Confusion
  • Dizziness or feeling faint
  • Extreme tiredness
  • Irritability
  • Headache
  • Hunger
  • Light-headedness
  • Sweating
  • Tremor or shaking
  • Trouble sleeping
  • Weakness.

How do you treat reactive hypoglycemia?

Most people can manage their reactive hypoglycemia with lifestyle changes, for example:

  • Eat smaller meals and snacks about every 3 hours
  • Include a variety of foods in your diet, such as protein (meat and nonmeat), fruits and vegetables, dairy products, and whole grains
  • Avoid high sugar foods and highly refined carbohydrates, such as white bread
  • If you drink alcohol, eat food
  • Get regular exercise.

  • DiLonardo MJ. Dansinger M. What Is Reactive Hypoglycemia? January 03, 2020, WebMD.
  • Vella A, Nathan D, Mulder J. Postprandial (reactive) hypoglycemia. Up to Date.

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