Severe hypoglycemia - complication of gastric bypass surgery

Physicians monitoring patients who have undergone gastric bypass surgery should be on the alert for a new, potentially dangerous hypoglycemia (low blood glucose) complication that, while rare, may require quick treatment, according to a new study by collaborating researchers at Joslin Diabetes Center, Beth Israel Deaconess Medical Center (BIDMC), and Brigham and Women's Hospital (BWH) and published in the October issue of the journal Diabetologia.

The paper follows on the heels of a Mayo Clinic report on six similar case studies published in July in the New England Journal of Medicine. About 160,000 people undergo gastric bypass surgery every year.

The study details the history of three patients, who did not have diabetes, who suffered such severe hypoglycemia following meals that they became confused and sometimes blacked out, in two cases causing automobile collisions. The immediate cause of hypoglycemia was exceptionally high levels of insulin following meals. All three patients in the collaborative study failed to respond to medication, and ultimately required partial or complete removal of the pancreas, the major source of insulin, to prevent dangerous declines in blood glucose.

"Severe hypoglycemia is a complication of gastric bypass surgery, and should be considered if the patient has symptoms such as confusion, lightheadedness, rapid heart rate, shaking, sweating, excessive hunger, bad headaches in the morning or bad nightmares," says Mary-Elizabeth Patti, M.D., Investigator in Joslin's Research Section on Cellular and Molecular Physiology and Assistant Professor of Medicine at Harvard Medical School. "If these symptoms don't respond to simple changes in diet, such as restricting intake of simple carbohydrates, patients should be evaluated hormonally, quickly," she adds. Dr. Patti and Allison B. Goldfine, M.D., also an Investigator at Joslin and Assistant Professor of Medicine at Harvard Medical School, were co-investigators of the study.

The study reported on three patients - a woman in her 20s, another in her 60s and a man in his 40s. All three lost significant amounts of weight through gastric bypass surgery, putting them in the normal Body Mass Index (BMI) range. Each, however, developed postprandial hypoglycemia (low blood glucose after meals) that failed to respond to dietary or medical intervention. As a result, all patients required removal of part or all of the pancreas. In all three cases, it was found that the insulin-producing islet cells in their pancreases had proliferated abnormally.

A potential cause of this severe hypoglycemia in these patients is "dumping syndrome," a constellation of symptoms including palpitations, lightheadedness, abdominal cramping and diarrhea, explains Dr. Patti. Dumping syndrome occurs when the small intestine fills too quickly with undigested food from the stomach, as can happen following gastric bypass surgery. But the failure to respond to dietary and medical therapy, and the conditions worsening over time suggested that additional pathology was needed to explain the symptoms' severity, Dr. Patti adds. "The magnitude of the problem was way beyond what doctors typically call dumping syndrome," she says.

Other causes of postprandial hypoglycemia can include overactive islet cells, sometimes caused by excess numbers of cells, a tumor in the pancreas that produces too much insulin, or familial hyperinsulinism (hereditary production of too much insulin), which in severe cases can necessitate removal of the pancreas.

In patients following bariatric surgery, additional mechanisms may contribute to overproduction of insulin. "First, insulin sensitivity (responsiveness to insulin) improves after weight loss of any kind, and can be quite significant after successful gastric surgery," says Dr. Patti. "Second, weight gain and obesity are associated with increased numbers of insulin producing cells in the pancreas, and so some patients may not reverse this process normally, leaving them with inappropriately high numbers of beta cells."

Finally, after gastric bypass surgery, GLP1 (glucagon-like peptide 1) and other hormones are secreted in abnormal patterns in response to food intake, since the intestinal tract has been altered. High levels of GLP1 may stimulate insulin secretion further and cause increased numbers of insulin-producing cells. "In our patients, the fact that the post-operative onset of hyperinsulinemia was not immediate suggests that active expansion of the beta cell mass contributed to the condition," Dr. Patti adds.

Other researchers participating in the study included S. Bonner-Weir, Ph.D., of Joslin; E.C. Mun, M.D., J.J. Holst, M.D., J. Goldsmith, M.D., D.W. Hanto, M.D., Ph.D., M. Callery, M.D., of Beth Israel Deaconess Medical Center. Collaborating investigators from the Brigham and Women's Hospital included R. Arky, M.D., who also is a Joslin Overseer, G.T. McMahon, M.D., M.M.Sc., A. Bitton, M.D., and V. Nose, M.D. All participants are on faculty at the Harvard Medical School. Funding for the study was provided by the National Institutes of Health, the Julie Henry Fund of BIDMC and the General Clinical Research Centers.

Besides helping afflicted gastric bypass patients, the research has hopeful implications for treating people with diabetes, says Dr. Patti. The gastric bypass patients have what many of those with diabetes lack - ample insulin - and perhaps an understanding of this phenomenon could be harnessed to help those with diabetes. "If we can understand what processes are responsible for too much insulin production and too many islet cells in these patients, we may be able to apply this information to stimulate insulin production in patients with diabetes, who lack sufficient insulin," Dr. Patti says.


  1. Larry W, Kyle Larry W, Kyle United States says:

    I had gastric bypass done in the end of 2004 and in 2005 starting passing out and haven't stop since. I think I finally found a answer to my problem. Now I need to talk to my doctor and see if the operation is what I need to get my life back. Thank-you.

  2. Lis acin Lis acin United States says:

    I had severe neurological damage because of Hypoglycemia after gastric bypass surgery. My pancreas was putting out 10X too much insulin every time I ate. A surgeon at the Mayo clinic told most people who have their pancreas removed have returning neurological issues with in 2-4 years. After reading an article from Stanford University by Dr Tracy McLaughlin about reversing symptoms by inserting a GTube in the remnant stomach and taking nutrition that way was successful. I had it done in May and am doing very well. I travel all over the world because of my job. I would highly recommend this option.


    • Connie Connie United States says:

      Hope this note finds you doing well. So nice to hear someone else has experience the same problems.  It took almost 7 years for me to find out what was going on.  I also have been to the Mayo Clinic (Jacksonville, Fla.)They said  no cure, did not recommend surgery (pancreas).   Can you tell me more about the GTube? Was an option for me because I was losing so much weight.

      Thanks for your help.

  3. pat pat United States says:

    Thank you for this information now maybe my doctor won't dismiss my symptoms this time as just something I have to deal with from my surgery. sitting here sweating in a 70 degree room 1 hr after eating now I know why1

  4. OMG
    Lauren Bell Lauren Bell United States says:

    I like Larry had bypass in March of 2004 and here it is in 2012 I have stopped losing weight even after being extremely active.  I in fact have gain weight which I knew something was wrong when I am spending 3 to 4 hours on the Tennis court and my weight is not moving dispite my gallons of sweat pouring off.  Just had a 2 hour glucose tolerance test and after one hour my BG was 50 after two hours I had dropped to 40.  this is a problem.  Thank you guys for sharing your stories.  I am relieved and have somewhere to go with this information.

    Internally Grateful.
    Lauren B.

    • Bonnie Sparks Bonnie Sparks United States says:

      I too had surgery in 2004--must have been a bad year.  About 5 years ago I began to have moments of tingling lips and tongue which I asked my doctors about.  They even ran a seizure test..could not figure out what I was referring to.  I asked my family doctor for Metformin to jump start some weight loss--since I was still 50 pounds from what I wanted to be.  She gave me a test set at the time also.  At that time my episode were about every 6 weeks.  Checked it one day for 'fun' when I was feeling my head thing.  My Blood reading was in the 50's...SURPRISE !!  And it has gone downhill since.  I now can get drops every day even watching the carb intake.  Last week I traveled to Indianapolis to see an endo DR who has many cases like this.  She ordered loads of blood work..waiting for results.  At least she was able to explain why this is happening--700 gut neuropeptides have been removed..which regulate tons of stuff--all now working aganist me.  I, unfortunately, am the only patient of my by-pass surgeon with this problem.  On restricted 15 gr of carb a meal (x 6).  Hoping it helps !!  She her again in 3 months.

  5. Jessica Elmore Jessica Elmore United States says:

    I'm so happy to have found others like me! I had gastric bypass in 6/06 went from 400lbs to 240lbs & got pregnant. I was feeling lightheaded, dizzy, lips tingling, tongue going numb, etc. 6/07 I got up in the middle of the night sweltering, disorinated & wanting a drink. I remember waking up on the ground which we all chalked up to being pregnant & the hot summer but it never happened again. When my daughter wasn't even a year old in 7/08 45mins after eating a wholesome meal my blood sugar plummeted while shopping with my daughter. It was caught on survailence I had a grandmal seizure; I am not epileptic. Paramedics tested my blood sugar it was 22! I was stripped on my license, had to battle with the department of motor vehicles, have countless test & see a neurologist. Life has continued to be one battle after another. My sugar drops almost on a daily occasion. About six months back I woke up to get a drink & use the restroom, I felt like I was spinning & falling. I yelled out to my fiance who got to me just as I fell delirious. Two weeks ago while on vacation in NYC less than an hour after eating a wholesome meal I felt "the symptoms" & told my fiance to hold on I needed to take some glucose tabs. I apparently got two in my mouth before having a seizure with my eyes in the back of my head, my limbs constricted & gurgling. Paramedics said the glucose tabs saved my life & I escaped with only a broken rib & mass bruising from falling. I'm trying to make it thru the days until I can see the endocrinologist now still dealing with low sugar (was just 41 after having soup & sandwich for lunch) while being a Mom to two autistic toddler children ages 3 & 5 & having panic attacks every time I feel the slightest sign. I cry all the time as secretly as I can not to alarm anyone but I'm terrified. I don't want my children to see their mother collapse, seize or die. I feel so alone, I'm getting afraid to go anywhere alone or even otherwise. It just sucks!

    • deby simpson deby simpson United States says:

      Lost 125 lbs and met my goal weight.  Had very few complications after surgery except belching.  Was told I needed a hysterectomy because enlarged uterus and large fibroids.  I guess it was enlarged cause I was told it is normal to have a 2 lb uterus and mine was 6 lbs.  Weird thing though,  never had any problems with low blood sugar until 3 days after the surgery.  They absolutely refuse to believe the surgery had anything to do with it.  I believe now there is lots of room for everything else so it has room to travel faster.  With uterus in, everything was bunched up and tight.  So now I have hypo with the perfect diet of high grains and complex carbs.  I can be great for weeks and then all of the sudden, I feel different but can't explain it.  No symptoms before it hits and then sweats come and its almost too late.  Comes in just minutes and blood level is around 40.  What works food wise for diabetics throws me into hypo within 15 minutes.  It scares the crude out of you because it hits without warning and hard and fast.  I carry nut bars and glucose tabs wherever I go.  I feel for you all.  It can be intimidating and make you paranoid.  Don't give up though, just become more self aware and slow down to recognize the symptoms and always, always carry extra food, juice and glocuse tablets wherever you go. Exercise is important for control.  Just make sure that you check before, 10 minutes after and keep rechecking.

  6. Sandra Davidson Sandra Davidson United States says:

    I am 8 months post surgery. Last month or so these too have been my symptoms. I have 4 docs with their irons in the fire. Don't know who to contact first. All of them.  Tomorrow. So glad I found this information tonight.

  7. Jessica Lopez Jessica Lopez United States says:

    Thank you all for the information. I was so relieved this morning to see that I was not alone.. I didn't understand why at 12 am. I was waking up to low levels.(42) I had tried to make sense of my eating habits and I attributed the levels to poor eating after 4 yrs of feeling fine. I had a 12 pound weight gain within the last year and I didn't understand how if I ate so little I could be GAINING weight again. I lost 156 bounds and found myself creeping up the scale in the last few months along with the bouts of low level readings. I have began to be fearful because I cannot predict when they are coming on? I understood that during the day it could be "what" I was eating but in the last week the 12 am wake ups to sweating, racing heart beat and confusion and the desperate need for food were becoming regular. I so scared now that I know I can pass out or have seizures. Glucose tabs and a low carb diet are my next move along with informing my doctor of what I read. I have seen her twice and of coarse in the moment my levels were always fine. uhg! Prayers please and I hope to get this under control with the few simple suggestions from here. THANK YOU!

  8. Deepak Shrivastava Deepak Shrivastava India says:

    I am 48 years and 1 year ago i had gastric bypass surgery. 1 year after the surgery  every thing is ok but after that i had a problem of low blood sugar so need a urgent answer that what should i do in this case ????

  9. Carol Buczek Carol Buczek United States says:

    I had bypass surgery in 2001.  In the last few years I have been diagnosed with anemia, which required iron infusions.   This is followed yearly by my hemotologist.  I have also discovered that I have osteoporosis and osteomalasia so taking double calcium citrate and can't wait for my next bone density.  I'm hoping for good news on this. I had some high numbers which indicated pancreatitis.   After a CAT scan the gastroenterologist said that nothing to do until I get horrible pain that won't go away.  I think I have had a few attacks more recently, one so bad I couldn't stand up and had a hard time breathing.  Scared the ----out of me.  I dont know if I passed out or the heating pad I had right there by my bed made it better.   I just remember laying there.

    Now I have a question... Has anyone, since having bypass surgery, found themselves waking during the night for food?  I never did that at all before surgery,   But now I will wake up, go to kitchen for something simple to eat (usually something sweet), then go back to bed and back to sleep.  This has become a real issue for me and I don't know how to stop it.   Never ever did that prior to my bypass surgery.  Any suggestions?  I'm not gaining weight, but it does interrupt sleep pattern.

  10. Vicky Holloway Parsons Rose Vicky Holloway Parsons Rose United Kingdom says:

    My symptoms are all from dumping syndrome and hypoglaciemia but my local gp don't know nothing about gastric bypas ut said I ain't got diebietas but I so sure I have hypoglaciemia as all hell he symto s are there pl are help any feed back will help v rose

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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