After bariatric surgery, a person might experience hypoglycemia. This may occur due to changes in how the body processes food following surgery. Often, making dietary changes can help manage the symptoms.

Hypoglycemia refers to low blood sugar levels. Health experts typically define hypoglycemia in people without diabetes as glucose levels falling below 55 milligrams per deciliter (mg/dL). However, healthy levels of glucose can vary from person to person, especially if a person has a condition such as diabetes.

A gastric bypass is a common operation that can help a person with weight loss. A surgeon will place surgical staples at the top of the stomach to create a pouch and then connect the pouch to the small intestine, which bypasses the stomach. This reduces the size of the stomach, meaning a person may feel full more quickly and absorb fewer calories.

In this article, we will discuss why hypoglycemia may occur after a gastric bypass, in addition to symptoms, treatment, and possible methods of prevention.

A person eating-2.Share on Pinterest
Ana Rocio Garcia Franco/Getty Images

Reactive hypoglycemia is a rare form of hypoglycemia, which doctors classify as nondiabetic hypoglycemia. It can happen following stomach surgery, as food may pass too quickly into the small intestine. It generally occurs when blood sugar levels fall below 55 mg/dL. Symptoms typically appear within 2–5 hours of eating a snack or a meal.

Although rare, reactive hypoglycemia is a potential complication of gastric bypass surgery. Studies suggest that reactive hypoglycemia occurs in 13.1% of people following gastric bypass surgery.

After a gastric bypass, the body may move the contents of the reduced stomach into the first section of the small intestine too quickly. This is also known as dumping syndrome or rapid gastric emptying. The gut may then release gut hormones that alter how the body digests glucose. This can cause glucose levels in the blood to fall.

Reactive hypoglycemia typically starts to occur 1–2 years after gastric bypass surgery but can happen at any time.

There is not much research into why some people develop reactive hypoglycemia after a gastric bypass. However, some studies suggest that a person may be more at risk of developing reactive hypoglycemia after a gastric bypass if any of the following are true:

  • They are female.
  • They are Caucasian.
  • They had symptoms of hypoglycemia before gastric bypass surgery.
  • They have lost an excessive amount of weight following gastric bypass surgery.
  • It has been over 3 years since their gastric bypass surgery.

A person may be experiencing reactive hypoglycemia if their blood glucose levels have dropped below 55 mg/dL, and it is 2–5 hours since they last ate a snack or a meal.

Other symptoms a person with reactive hypoglycemia may experience can include:

  • extreme tiredness or weakness
  • dizziness or light-headedness
  • excessive sweating
  • mood changes, such as irritability or anxiety
  • cravings for sugary foods
  • insatiable appetite
  • increase in heart rate
  • tingling lips
  • shaking or tremors
  • blurry vision

If a person experiences blood glucose levels of less than 55 mg/dL, they should follow the rule of 15. These guidelines suggest that a person consume a 15-gram portion of fast-acting glucose, such as half a cup of juice or soda or a glucose tablet. If after 15 minutes blood glucose levels are still low, a person can have another serving.

Once blood glucose levels have returned to a healthy level, a person can consume a snack containing slow-release carbohydrates, such as fruit or cereal. This may prevent blood glucose levels from dropping again.

Read more about treating a hypoglycemic episode.

Typically, changes in diet are the most effective way to help prevent reactive hypoglycemia. Changes a person can make to their diet can include:

  • Following a healthy, balanced diet: This can involve consuming the equivalent of 1.5 to 2 cups of fruits and 2 to 3 cups of vegetables per day; small amounts of unsaturated fats, such as olive oil and avocados; lean protein, such as meat, poultry, and eggs with every meal; and minimal sugar.
  • Eating small amounts regularly: Eating 5–6 small meals and snacks per day may help regulate the amount of glucose in the bloodstream.
  • Avoiding big portions of refined carbohydrates: Consuming smaller portions of foods such as potatoes, pasta, bread, and rice throughout the day can help reduce reactive hypoglycemia.
  • Consuming low glycemic foods: Foods such as oats, whole grains, beans, and pulses take longer to digest, so they can help release glucose more slowly.
  • Limiting caffeine and alcohol intake: A person can choose decaffeinated versions of tea, coffee, and soda, and limit alcohol intake to help reduce symptoms.

If a person is still experiencing symptoms after adjusting their diet, a doctor may prescribe antidiabetic drugs, such as metformin, to help a person manage their blood sugar levels.

Reactive hypoglycemia may occur after gastric bypass surgery due to changes in the way the body absorbs and digests glucose. Symptoms typically start to occur 1–3 years after the procedure, and symptoms may present 2–5 hours after consuming food.

The most effective strategy to help prevent reactive hypoglycemia after a gastric bypass is to make dietary changes. A person can discuss these modifications with their doctor.