What Is Reactive Hypoglycemia? (2024)

Reactive hypoglycemia, also called postprandial hypoglycemia, is when your blood sugar (blood glucose) drops after eating. This "sugar crash" usually occurs within a few hours of eating. Why it happens is still under study, but it typically resolves quickly with a small amount of food or drink, like orange juice, or with glucose gel.

People who don't have diabetes experience reactive hypoglycemia, but they may be more at risk of developing diabetes if factors like a family history are present. It can occur after bariatric (weight loss) surgery or, rarely, due to insulinoma (endocrine tumor). Sometimes, though, an episode of reactive hypoglycemiacan occur with diabetes due to exercise levels, or when too much insulin is taken before a meal.

Symptoms and Signs

Hypoglycemia is the medical term for low blood sugar, with symptoms that typically occur when glucose levels drop below 70 milligrams per deciliter of blood (mg/dL).

Common symptoms of reactive hypoglycemia include:

• Anxiety, sense of panic, shaking or tremors
• Sweating or clammy skin
• Irritability or restlessness
• Confusion
• Rapid heartbeat
• Dizziness
• Hunger
• Nausea

Reactive hypoglycemia occurs after a meal. Its causes are different from hypoglycemia that occurs due to fasting for long periods without food, or in most situations where people diagnosed with diabetes are working to manage their blood sugar levels.

The symptoms of reactive hypoglycemia are rarely life-threatening but may be a sign of an underlying medical condition such as Addison's disease. If severe symptoms occur, seek immediate medical care.

Causes

Triggers for reactive hypoglycemia can include eating high-carbohydrate meals or snacks. One theory as to why it occurs is that when a person eats carbs with a high glycemic index, the body produces enough insulin to combat hyperglycemia.

However, the body is not prepared for a crash because glucagon, which can counteract the action of insulin, is not adequately produced. Therefore, when blood sugar does go down, the body does not bring up the sugar by gluconeogenesis or glycogenolysis, which are processes that produce blood glucose from stored materials in the body.

Health conditions other than diabetes that are known to cause reactive hypoglycemia can include:

• Certain cancers: The deficiency of certain digestive enzymes or hormones can be due to chronic conditions like pancreatic cancer. These endocrine problems interfere with the body's ability to break down food. This, in turn, can reduce the amount of glucose available in the body.
• Addison's disease: People diagnosed with Addison's disease have a deficiency of hormones produced by the adrenal glands. This, in turn, can increase a person's sensitivity to insulin.
• Insulinomas: These rare, non-cancerous tumors in the pancreas can cause overproduction of insulin. The overproduction, in turn, causes a drop in blood sugar. Insulinoma usually causes fasting hypoglycemia, though postprandial hypoglycemia can occur.
• Stress: Although there isn't a definite link, stress may affect your blood sugar because it causes a rush of adrenaline. This releases glucose into the bloodstream from temporary storage sites in your body, thereby increasing blood sugar levels. Stress can also cause some people to overeat in response to increased cortisol, which can spike blood sugar levels.
• Bariatric surgery: Also called gastric bypass surgery, this treatment typically used for severe obesity can lead to reactive hypoglycemia as a complication. Food passes more quickly and changes how glucose is used. Some people can have similar responses due to early or late dumping syndromes caused by other digestive changes or surgeries.
• NIPHS: Non-insulinoma pancreatogenic hypoglycemia syndrome (NIPHS) is a rare condition that can lead to reactive hypoglycemia. It can occur after bariatric surgery, but that's not always the cause.
• Genetic changes: Research has identified genetic mutations that lead to reactive hypoglycemia with other symptoms, including long QT syndrome (a cardiac condition).

Diagnosis

Reactive hypoglycemia can be diagnosed using an oral glucose tolerance test (OGTT) or a mixed meal tolerance test (MMTT).

The OGTT includes only glucose. The MMTT is performed by feeding the person a beverage rich in protein, carbohydrates, and fat (such as Ensure or Boost). Glucose and insulin levels are then assessed.

The healthcare provider will look for results, often called the Whipple's Triad, that include:

• Symptoms known or likely to be caused by hypoglycemia
• Low plasma glucose measured at the time of the symptoms
• Relief of symptoms when glucose is raised to normal

Results from tests used to diagnose hypoglycemia also can help your healthcare provider to rule out other possible causes of the symptoms, including mental health concerns like anxiety.

Treatment

Treatment for reactive hypoglycemia will depend on the cause. In many cases, blood sugar can be corrected quickly and people don't need medical treatment. However, if the symptoms are recurring, they may be the result of an underlying condition that needs treatment.

If you have an episode of reactive hypoglycemia, you can use food to help restore normal blood sugar levels.

This is accomplished with the "15-15 Rule," which involves eating 15 grams of fast-acting carbohydrates and checking your blood sugar 15 minutes later to see if the levels have normalized. The American Diabetic Association recommends:

• Glucose tablets or a gel tube, administered per the directions
• 4 ounces of juice or regular soda
• 1 tablespoon of sugar, honey, or corn syrup
• Hard candies, jellybeans, or gumdrops
  

Once your symptoms have eased, have a snack if your next meal is more than an hour away to prevent your blood sugar from dropping again.

For an underlying medical condition, the treatment will focus on resolving or managing the condition. This may include the surgical removal of an insulinoma or, in the case of NIPHS, the partial removal of the pancreas.

Prevention

Certain dietary and lifestyle changes may reduce the odds of a reactive hypoglycemia episode, even where the cause is not yet known. You can try:

• Adopting a diet with lean protein, whole grains, vegetables, fruits, and low-fat dairy
• Eating smaller meals more often
• Avoiding alcohol and sugary mixers on an empty stomach
• Getting more exercise
• Managing stress

Talk to your healthcare provider about your symptoms and lifestyle changes, as it's possible that medication or other measures may be needed, too.

Summary

Reactive hypoglycemia is a drop in blood glucose (sugar) that occurs after eating. Symptoms usually develop within a few hours of consuming food and may include shakiness, dizziness, nausea, rapid heartbeat, and sweating. Severe cases can lead to fainting or seizures.

Reactive hypoglycemia can occur for other reasons beyond diabetes. The treatment typically involves eating fast-acting carbohydrates that can quickly bring blood sugar levels back to normal.

By Debra Manzella, RN
Debra Manzella, MS, RN, is a corporate clinical educator at Catholic Health System in New York with extensive experience in diabetes care.