Reactive Hypoglycemia Overview

Blood Sugar Drops After Eating

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Reactive hypoglycemia, also called postprandial hypoglycemia, is when your blood sugar (blood glucose) drops after eating. Sometimes referred to as a "sugar crash," reactive hypoglycemia usually occurs within four hours of eating.

Reactive hypoglycemia is one of two types of hypoglycemia unrelated to diabetes. The other is known as fasting hypoglycemia, which happens when you don't eat for a long time or have certain medical conditions.

The cause of reactive hypoglycemia is often unknown, although there are a handful of medical conditions associated with it. The treatment is typically focused on normalizing blood glucose levels by consuming a small amount of a sugary food or beverage.


Verywell / Alex Dos Diaz

This article explains what reactive hypoglycemia is and how it differs from hypoglycemia in people with diabetes. It also outlines the symptoms, causes, and methods of diagnosing and treating this uncommon form of hypoglycemia.

What Is Hypoglycemia?

Hypoglycemia is the medical term for low blood sugar, with the prefix hypo- meaning "low" and glycemia referring to the presence of glucose in the blood. Glucose is one of the main sources of energy for the body.

Hypoglycemia occurs when blood glucose levels drop below normal. Symptoms of hypoglycemia typically occur when glucose levels drop below 70 milligrams per deciliter of blood (mg/dL).

Hypoglycemia is common in people with diabetes, who may experience a drop in blood sugar due to high insulin doses, among other things. But, hypoglycemia can also affect people who don't have diabetes for entirely different reasons.

Reactive Hypoglycemia
  • Usually happens after eating high-carbohydrate meals

  • Could indicate pre-diabetes or being at risk for diabetes

  • May be caused by a history of stomach surgery

Fasting Hypoglycemia
  • Occurs after a long period of time without eating

  • Could be caused by certain medications, alcohol, or illnesses that cause low glucose

  • May be caused by low levels of hormones

Reactive Hypoglycemia

Reactive hypoglycemia is a type of non-diabetic hypoglycemia.

Reactive hypoglycemia occurs exclusively after eating food. By contrast, hypoglycemia in people with diabetes is often caused by postponing or skipping meals.

Hypoglycemia in people with diabetes can also occur if they take too much insulin or diabetes medications or if they exercise vigorously without adjusting their medications or eating more food.

Reactive Hypoglycemia Symptoms and Signs

Reactive hypoglycemia can cause symptoms ranging from mild to severe. It is rarely life-threatening but may be a sign of an underlying medical condition.

Common Symptoms

Symptoms of this condition vary by how rapidly or severely blood sugar levels drop. As such, what reactive hypoglycemia feels like can differ from person to person and even episode to episode in the same person.

Some symptoms of reactive hypoglycemia include:

  • Shaking or tremors
  • Hunger
  • Rapid heartbeat
  • Anxiety or panic
  • Tingling near the mouth
  • Sweating
  • Headache
  • Fatigue
  • Inability to concentrate
  • Dilated pupils
  • Irritability
  • Restlessness
  • Nausea
  • Dizziness
  • Weakness
  • Loss of muscle control

Severe Symptoms

If the drop in blood sugar is severe, it can cause profound and even debilitating symptoms. This is particularly true if the person is dehydrated.

Severe symptoms of reactive hypoglycemia include:

  • Confusion
  • Changes in behavior
  • Slurred speech
  • Clumsy movements
  • Blurry or double vision
  • Seizures
  • Loss of consciousness

When to See a Healthcare Provider

Generally speaking, a single episode of reactive hypoglycemia is not a cause for alarm unless the symptoms are severe, such as passing out or experiencing a seizure. Severe symptoms are most likely to occur if a person is dehydrated, which in itself may require treatment.

Recurrent episodes should never be overlooked. While it is possible that dietary habits are contributing to the episodes, the bigger concern is that a recurrent drop in blood sugar may be a sign of an undiagnosed medical condition, such as Addison's disease or pancreatitis.


Reactive hypoglycemia can be diagnosed by measuring the amount of glucose in a person's blood while they are having symptoms. If the blood glucose level is below 70 mg/dL, your healthcare provider may recommend a mixed meal tolerance test (MMTT).

The MMTT is performed by feeding the person a beverage rich in protein, carbohydrates, and fat (such as Ensure or Boost). After drinking the beverage, blood glucose levels are retested every 30 minutes for five hours.

In addition to glucose, the MMTT will monitor insulin levels in the blood. This is a hormone produced by the pancreas that helps regulate blood sugar.

Conditions That Can Mimic Hypoglycemia

Conditions other than hypoglycemia can have some of the same symptoms, including dizziness, weakness, sweating, and rapid heartbeat.

These include a wide variety of conditions, such as:

To decide if your symptoms are due to hypoglycemia, your healthcare provider will look for signs of the "Whipple Triad."

This includes:

  • Symptoms of hypoglycemia
  • Low plasma glucose measurements while you have symptoms
  • No symptoms when your glucose increases to normal levels

Without these three indications, your healthcare provider will likely evaluate you for other conditions that have similar symptoms.

Reactive Hypoglycemia 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 that 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.

There are several other conditions that are known to cause non-diabetic hypoglycemia.

Among them:

  • The deficiency of certain digestive enzymes can interfere with the body's ability to break down food. This, in turn, can reduce the amount of glucose available for absorption in the intestines. Causes include chronic pancreatitis, cystic fibrosis, and pancreatic cancer.
  • Late dumping syndrome can cause symptoms similar to those of reactive hypoglycemia after gastric bypass surgery. This complication of the surgery is when food passes through the digestive tract so quickly that not enough glucose is derived from food. Early dumping syndrome occurs when large amounts of food from your stomach move faster than normal into your duodenum, and it is unrelated to blood sugar levels.
  • Addison's disease causes a deficiency of hormones produced by the adrenal glands. This, in turn, can increase a person's sensitivity to insulin.
  • Insulinomas are rare, non-cancerous tumors in the pancreas that causes the overproduction of insulin. The overproduction, in turn, causes a drop in blood sugar. However, insulinoma usually causes more pronounced fasting hypoglycemia rather than in-between-meal hypoglycemia.
  • Non-insulinoma pancreatogenic hypoglycemia syndrome (NIPHS) is another rare condition that causes changes in the pancreas, leading to the overproduction of insulin.
Too much insulin intake can cause lower levels of glucose in the blood.

Reactive Hypoglycemia Treatment

If an underlying medical condition is causing reactive hypoglycemia, the treatment will be focused 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 itself.

For all other cases, there are two aspects of treatment. The first is knowing how to respond to hypoglycemic episodes. The second is making changes to prevent future episodes.

What to Eat During an Episode

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.

Carbohydrates ('carbs") are essentially sugar molecules. Fast-acting carbohydrates are certain types of foods or beverages that can quickly raise the blood sugar level. 

If the blood glucose level is still below 70 mg/dL after 15 minutes, you would eat another serving and check again in 15 minutes.

Recommended Fast-Acting Carbs

  • Banana (half)
  • Corn syrup (1 tablespoon)
  • Fruit juice (1/2 to 3/4 cup)
  • Glucose gel (1 small tube)
  • Glucose tablets (3 to 4 tablets)
  • Honey (1 tablespoon)
  • LifeSavers (6 to 8 candies)
  • Orange juice (1/2 cup)
  • Raisins (2 tablespoons)
  • Nonfat milk (1 cup)
  • Soda with sugar (1/2 cup)
  • Sugar (1 tablespoon or 5 sugar cubes)
  • Syrup (1 tablespoon)

Once your symptoms have eased, eat a small snack or meal to prevent your blood sugar from spiking and dropping again.

Some good options include:

  • Banana
  • Berries
  • Orange or clementine
  • Snack bar


The cause of reactive hypoglycemia in most cases is unknown. Even so, certain dietary and lifestyle changes may reduce the odds of it happening again.

Reactive Hypoglycemia Diet

Among the diet recommendations your healthcare provider may give you:

  • Eat a balanced diet that includes lean protein, whole grains, vegetables, fruits, and low-fat dairy.
  • Limit foods that have a high glycemic index (GI). These are foods that cause a rapid increase in blood sugar followed by a rapid decline.
  • Eat small, frequent meals that include fiber and protein.
  • Do not go longer than three hours without eating.
  • Avoid alcohol on an empty stomach, and avoid sugary mixers.

Physical Activity

In addition, you should exercise regularly. Physical activity increases the amount of glucose taken up from the blood. This, in turn, helps stabilize insulin levels.

If you're just starting to get active, remember to work your way up to increasing your activity. It's also worth consulting with your healthcare provider before beginning.


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

Reactive hypoglycemia is not related to diabetes, and the cause of most episodes is unknown. The treatment typically involves eating fast-acting carbohydrates that can quickly bring blood sugar levels back to normal.

A Word From Verywell

If you experience the symptoms of hypoglycemia after you eat, speak with your healthcare provider. This is particularly true if your symptoms are severe or recurrent.

Symptoms of hypoglycemia can mimic those of other diseases, including liver cirrhosis and anxiety. In the end, something that you may think is a "sugar crash" may end up being something entirely different.

Frequently Asked Questions

  • Is reactive hypoglycemia a type of diabetes?

    No. Reactive hypoglycemia is one of two types of non-diabetic hypoglycemia. Reactive hypoglycemia occurs after eating, while hypoglycemia in people with diabetes can occur when meals are skipped or delayed.

  • How do you test for reactive hypoglycemia?

    If reactive hypoglycemia is suspected based on blood glucose results, your healthcare provider can recommend a mixed meal tolerance test (MMTT). This involves feeding you a carbohydrate-rich drink and retesting the blood every half hour to see if glucose levels return to normal.

  • How long does reactive hypoglycemia last?

    It depends on how low the glucose levels have dropped. If the glucose levels are extremely low and left untreated, fainting and even seizures can occur. If treated with fast-acting carbohydrates, a person may recover within 15 minutes.

  • Does reactive hypoglycemia turn into diabetes?

    Generally, no. With reactive hypoglycemia, eating food triggers a drop in blood sugar. In people with diabetes, eating food is more likely to trigger an increase in blood sugar.

  • What foods should I avoid with reactive hypoglycemia?

    Limit high glycemic index (GI) foods that cause blood sugar levels to rise and then fall precipitously. These include white bread, white rice, cakes, cookies, potatoes, fast food, chips, and sweetened yogurt. It even includes certain fruit, like watermelon and pineapple.

  • Can stress cause reactive hypoglycemia?

    There isn't a definite link, but stress can 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 you to overeat in response to increased cortisol, a stress hormone, which can lead to a spike in blood sugar.

  • Is reactive hypoglycemia serious?

    In some cases, reactive hypoglycemia can cause severe symptoms, such as fainting or seizures. It isn't usually life-threatening, but it can be a sign of a serious medical condition, such as prediabetes.

  • Can reactive hypoglycemia go away on its own?

    Yes. Most of the time, you won't need medical treatment for reactive hypoglycemia. However, if the symptoms are recurring, they may be the result of an underlying condition that needs treatment.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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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.