April 2012 – Hypoglycemia: A Result of Gastric Bypass Surgery

Two studies were recently published in The New England Journal of Medicine. The findings caused a stir among lay, medical and media alike…that Type 2 diabetes, or “diabesity,” could be cured with gastric bypass surgery.

I am not here to post the pros and cons of what has been written, but I do have some important information for anyone who has had gastric bypass surgery or is contemplating doing so.

In the past 10 years, an increasing number of concerned patients contacted the HSF because they had gastric bypass surgery and were now experiencing hypoglycemia symptoms ranging from mild to severe. It was then that I approached Dr. Mark Lamet, a gastroenterologist who practices in Hollywood, Florida, and asked if he would write an article for our members. He wrote the following in 2005 and recently edited it again after I suggested we reprint it due to renewed interest and concern.

At the HSF, we believe it is imperative that, as a patient, you become involved in your own decisions concerning health care. We hope the information we provide empowers you with the knowledge to make informed choices.


Gastric bypass or bariatric surgery has over the last few years become a popular and usually successful therapy in the battle against obesity. The procedure is not, however, without the risk of serious side effects or complications. Investigators have recently noted a relationship between gastric bypass surgery and symptomatic hypoglycemia and in rare cases the development of nesidioblastosis, (a hypofunction of insulin producing cells) in patients who have undergone this surgical procedure.

Three theories have been proposed to explain the unheralded appearance of functional hypoglycemia and the patient who did not previously suffer from this disorder.


An intact stomach acts as a warehouse where food is stored, mixed with gastric juices, and slowly released through the pyloric channel into the small bowel where absorption of nutrients occurs. The pyloric channel (or pylorus) acts as a valve that controls the release of food into the small bowel. In gastric bypass surgery (and other types of gastric surgery) the pylorus is resected and its absence allows the food to exceed the stomach in a rapid and uncontrolled fashion (hence the term dumping). This leads to abnormally quick absorption of nutrients, triggering an excessive insulin release and resultant hypoglycemia.

Other causes of hypoglycemia postulated for the patients who have undergone gastric bypass surgery include:

a. Improved insulin sensitivity as a result of weight loss.

b. Obesity is associated with an increased number of insulin producing cells in the pancreas (beta cells). Some patients may not reverse this process after surgery and weight loss leaving them with an inappropriate high number of beta (insulin producing) cells.

c. Finally, the secretion of certain gastrointestinal hormones appears to be excessive in post-gastric bypass patients or GLP1 (Glucagon-Like Peptide-1) and other hormones are found in abnormal patterns in response to food intake since the intestinal tract has been altered. High levels of GLP1 may stimulate insulin secretion leading to hypoglycemia.

It has been recommended that all patients undergoing gastric bypass surgery be informed of the possibility of developing hypoglycemia and its resultant symptoms, which reportedly can be severe leading to profound confusion and even loss of consciousness. Should these symptoms develop, a consultation with an endocrinologist is imperative so that the etiology of the hypoglycemia can be determined and appropriate therapy recommended.

In contrast to functional hypoglycemia in patients who have not undergone gastric bypass surgery, the glucose tolerance test (GTT) is not helpful in confirming the diagnosis. Without the pyloric valve, introducing a large volume of glucose into the intestinal tract will surely induce hypoglycemia and in the majority of patients can induce severe reactions.

Additionally, in severe cases (i.e. nesidioblastosis), a cure for the hypoglycemia may require pancreatic resection.

For mild cases restriction of simple carbohydrates (sugar, white flour, alcohol) is usually adequate in curbing hypoglycemic events. Should symptoms not respond, an immediate consultation with the appropriate expert is recommended.

To summarize:

1. Postprandial (after eating) hypoglycemia has been recognized as a side effect of gastric bypass surgery.

2. The drop in blood sugar in rare patients can be severe and life threatening.

3. Numerous different mechanisms have been proposed as an etiology for this phenomenon and seeking appropriate medical consultation to determine the etiology is imperative.

4. Dietary restrictions (hypoglycemic diet) should be tried first, modified to include frequent small meals. A diet high in protein and fiber, which includes carbohydrates low on the glycemic index scale, should control the symptoms of functional hypoglycemia.

5. Should symptoms continue or be severe, then more definitive therapy might be indicated.

Mark Lamet, M.D., F.A.C.G.

ML: vas


I am sorry but due to the huge number of e-mails I receive, it is impossible for me to answer them all. If you e-mail me and don’t receive a quick response, please don’t wait. Seek medical attention . . . especially if you have severe symptoms!

Here’s to your health,




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