Eating foods high in carbs can spike blood sugar levels. Rebound hypoglycemia occurs when blood sugar sharply drops as the body overcompensates for the spike. Severe symptoms and persistent episodes merit a visit to a doctor.

Rebound hypoglycemia is more commonly known as reactive hypoglycemia. It can cause symptoms like lightheadedness or shakiness within hours of consuming a high carb meal. It may be more common when exercising shortly after eating.

The condition can occur in people with or without diabetes and with no associated medical conditions. The underlying cause may not be as clear in people without diabetes, though it probably occurs due to the overproduction of insulin.

Rebound hypoglycemia usually resolves on its own without any long-term complications. Consuming sugary foods and beverages like orange juice can help raise your blood sugar levels again and improve your symptoms.

Rebound or reactive hypoglycemia is when your blood sugar rapidly drops after a period of hyperglycemia (high blood sugar).

  • Hyperglycemia is often defined as a blood sugar concentration over 7.8 millimoles per liter (mmol/L), or 140 milligrams per deciliter (mg/dL).
  • Hypoglycemia is often defined as a blood sugar concentration under 3.3 mmol/L, or 60 mg/dL. If your blood sugar levels drop below 3.9 mmol/L, or 70 mg/dL, you may develop symptoms.

Rebound hypoglycemia occurs within minutes to hours of consuming a food that raises your blood sugar levels. It’s particularly common after consuming sugar or a meal that contains a high amount of carbs.

No standard definition of rebound hypoglycemia exists. In a 2023 study, researchers defined it as low blood sugar that occurred within 120 minutes of blood sugar levels rising to over 10 mmol/L, or 180 mg/dL. They defined low blood sugar as below 3.9 mmol/L, or 70 mg/dL.

Reactive hypoglycemia can occur in people with no diabetes or associated health conditions. It also occurs in people with:

  • diabetes
  • prediabetes
  • gastrointestinal dysfunction, such as rapid gastric emptying
  • hormone imbalances

The underlying cause of reactive hypoglycemia in people without one of these conditions is often unclear. Delayed insulin secretion and increased insulin sensitivity may play a role.

Reactive hypoglycemia seems to commonly occur in people who do intense exercise shortly after consuming a high carb snack or meal or when prolonged and intense exercise depletes their blood sugar levels. People with higher insulin sensitivity may be more prone to exercise-induced reactive hypoglycemia.

Rebound hypoglycemia causes characteristic symptoms of low blood sugar in the minutes to hours after eating carbs.

Common symptoms of low blood sugar include:

If your blood sugar levels significantly drop, it’s possible to develop complications like seizures or coma. But it’s rare for your blood sugar to drop this low in the absence of an underlying medical condition.

You can usually manage rebound hypoglycemia by following the 15-15 rule. This rule says that you consume 15 grams (g) of carbs and check your blood sugar levels after 15 minutes. If you still have symptoms, you can try another 15-g serving.

Each item in the list below contains roughly 15 g of carbs:

  • 1/2 a cup of juice
  • a tablespoon of sugar or honey
  • three or four glucose tablets
  • a dose of glucose gel
  • hard candy, serving as per the label

Additionally, making some lifestyle changes may help you reduce and prevent symptoms. These may include:

  • eating smaller meals more frequently
  • minimizing your intake of sugary or high glycemic index foods
  • eating high carb foods together with:
    • protein
    • fat
    • fiber

Reactive hypoglycemia often doesn’t require long-term treatment. But if it’s a regular occurrence, you may benefit from a medical evaluation to screen for an underlying condition.

It’s also important to contact a healthcare professional if you develop:

  • low blood sugar levels that cause serious symptoms, like fainting or loss of consciousness
  • frequent bouts of low blood sugar levels
  • seizures

Here are some frequently asked questions that people have about reactive hypoglycemia.

What causes reactive hypoglycemia?

Reactive hypoglycemia may be due to your body’s overproduction of insulin in response to a high carb snack or meal that spikes your blood sugar levels. This overproduction of insulin causes your blood sugar levels to drop rapidly and significantly.

Can you reverse reactive hypoglycemia?

Usually, eating about 15 g of carbs and waiting 15 minutes balances your blood sugar levels.

Can you prevent nighttime hypoglycemia?

You may be able to prevent nighttime hypoglycemia by having a snack before you go to bed and regularly monitoring your blood sugar levels.

What is the Somogyi phenomenon?

The Somogyi phenomenon is the theory that when your blood sugar drops significantly while you’re sleeping, your body compensates by producing too many of the hormones that raise your blood sugar levels.

There’s still debate on the theory of the Somogyi effect, as recent continuous glucose monitoring studies have found conflicting evidence. Some researchers have noticed that people with high blood sugar levels in the morning tend to also have high blood sugar levels at night.

Rebound hypoglycemia, also called reactive hypoglycemia, occurs when your blood sugar levels drop within minutes to hours of eating a high carb snack or meal.

It seems to frequently occur in healthy individuals without a known underlying condition. It also seems to be particularly common when starting exercise shortly after eating a high carb meal.

Reactive hypoglycemia can also be a sign of some health conditions, such as diabetes, prediabetes, or gastrointestinal problems.