Reactive Hypoglycemia: Causes, How It Feels, Triggers

Reactive hypoglycemia, also called postprandial hypoglycemia, is a drop in blood glucose (blood sugar) after eating.

There are two types of hypoglycemia that are unrelated to diabetes. Fasting hypoglycemia happens when you don't eat for a long time or have certain medical conditions. Reactive hypoglycemia usually happens within four hours of eating. It's sometimes referred to as a "sugar crash."

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.

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.

Hypoglycemia occurs when blood glucose levels drop below a certain level that you need to take action to bring them back to normal. Glucose is one of the main sources of energy for the body.

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

Reactive hypoglycemia is one of two types of non-diabetic hypoglycemia. The other non-diabetic type is called fasting hypoglycemia.

Reactive Hypoglycemia vs. Hypoglycemia

Reactive hypoglycemia differs from hypoglycemia in that 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

Diagnosis

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:

• Anxiety
• Migraine headache
• Heat exhaustion
• Pancreatitis
• Lyme disease
• Pulmonary hypertension

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. There are theories as to why it occurs, including the deficiency of certain hormones or enzymes, but there remains little consensus among researchers.

There are several 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.
• Dumping syndrome can cause 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.
• Addison's disease can reduce the amount 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.
• 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.

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:

• Glucose tablets (see instructions)
• Glucose gel tube (see instructions)
• Juice or non-diet soda (1/2 cup)
• Sugar, honey, or corn syrup (1 tablespoon)

Lifestyle Changes

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. Eat food with alcohol, and avoid sugary mixers.
  

Physical Activity

In addition, you should exercise regularly. Physical activity increases the amount of glucose taken up by 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.

When to See a Doctor

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

On the other hand, 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.

Summary

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 heart failure. In the end, something that you may think is a "sugar crash" may end up being something entirely different.