Reactive hypoglycemia is low blood sugar that occurs a few hours after eating a meal. It happens when a person has too much insulin in their blood at the wrong time.

Insulin is the hormone that enables sugar to enter cells from the bloodstream. Within cells, sugar serves as the primary source of energy.

Symptoms of reactive hypoglycemia may include confusion, shakiness, and anxiety. A person can reduce the risk of reactive hypoglycemia by taking dietary measures, such as eating small, frequent meals and limiting the intake of sugary foods.

Keep reading to learn more about reactive hypoglycemia, including the causes, symptoms, and treatment options available.

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Hypoglycemia is the term for when blood sugar, or glucose, falls below the normal, healthy range. Some factors that affect blood sugar include:

  • exercise
  • the intake of sugar and other carbohydrates through the diet
  • the amount of insulin in the body

When a person consumes carbohydrates, the body breaks them down to form glucose. In response, the pancreas secretes the hormone insulin, which helps glucose pass from the blood into cells in the muscles, liver, and brain. To function properly, these cells need glucose for fuel.

There are different types of hypoglycemia. One type occurs in people who have diabetes, and doctors classify this as diabetic hypoglycemia. It happens when the insulin injections or antidiabetic medication that a person takes removes too much sugar from the bloodstream.

Reactive hypoglycemia is a rare form of the condition, which doctors classify as nondiabetic hypoglycemia. It occurs when blood sugar levels are below 70 milligrams/deciliter. This often occurs approximately 2–4 hours after a meal. Symptoms subside quickly after eating or drinking carbohydrates.

Researchers have not yet fully identified the specific causes of reactive hypoglycemia. However, the condition stems from having too much insulin in the bloodstream at the wrong time.

Possible causes include:

  • having prediabetes, which can make it hard for the pancreas to produce the right amount of insulin
  • having rare enzyme deficiencies, which can make it difficult for the stomach and intestines to break down food
  • having had stomach surgery, which can cause food to pass through the stomach into the intestines too fast

People with reactive hypoglycemia may experience some or all of the following symptoms 2–4 hours after a meal:

  • hunger
  • shakiness
  • fatigue
  • sweating
  • weakness
  • nausea or vomiting
  • mood swings
  • anxiety
  • fast heart rate
  • irritability
  • headaches
  • confusion

Most people who have reactive hypoglycemia do not require treatment. Rather, doctors recommend dietary changes to manage the symptoms.

That said, if a person needs immediate treatment, doctors advise eating or drinking something that contains 15 grams of carbohydrates. Half a cup of juice contains this amount, but the juice should be the regular variety rather than a low calorie version that contains fewer carbohydrates.

One study reports that certain people with reactive hypoglycemia may also benefit from taking antidiabetic drugs, such as metformin. These individuals include those who doctors suspect may have prediabetes. Metformin may help reduce symptoms, as prediabetes is a possible cause of this type of hypoglycemia.

The dietary practices below may help prevent symptoms of reactive hypoglycemia:

  • Eating small meals throughout the day: Eating a small amount of food every few hours can keep blood sugar from spiking as high as it does after eating a large meal.
  • Limiting the intake of sugary foods and beverages, such as desserts, sweet tea, and fruit juices: These foods can trigger an excessive increase in insulin, which can result in a quick drop in blood sugar.
  • Including lean protein and healthful fats in the diet: Examples of lean protein include fish and skinless poultry, while examples of healthful fats include avocados and olive oil.
  • Eating high-fiber foods: These include fruits, vegetables, beans, and whole grains.
  • Limiting or avoiding alcohol: Alcohol can cause low blood sugar. If a person wishes to drink alcohol, it is best to do so in small amounts and to eat something alongside it.
  • Limiting or avoiding caffeine: Coffee, tea, and some sodas contain caffeine. This stimulant can cause the same symptoms of low blood sugar.

Learn more about what to eat for hypoglycemia here.

According to one study, certain people with reactive hypoglycemia may benefit from diabetes-prevention lifestyle practices. These people include individuals who have risk factors for diabetes, such as overweight and a family history of the disease.

In addition to helping prevent the onset of diabetes, these practices may reduce symptoms of hypoglycemia. Aside from eating a healthful diet, the Centers for Disease Control and Prevention (CDC) recommend:

  • increasing physical activity
  • managing stress
  • getting support from others with similar challenges

If a person is experiencing the symptoms of reactive hypoglycemia, they should consult a doctor.

This will enable them to find out whether they have the condition and, if so, to know its degree of severity. An examination and testing can rule out prediabetes or other conditions that may be causing the blood sugar to drop too much.

If necessary, a doctor may refer an individual to other healthcare professionals. These may include a registered dietitian or an endocrinologist, who is a specialist in hormone imbalances.

Reactive hypoglycemia is low blood sugar that occurs several hours after a meal. Doctors classify it as a nondiabetic variety of the condition.

When someone has symptoms of reactive hypoglycemia, the immediate treatment involves consuming a small amount of a sugary food or beverage, such as half a cup of fruit juice.

Following a healthful diet may help prevent the sugar spikes in the bloodstream that lead to sugar dips and symptoms of hypoglycemia.