Bariatric Surgery FAQ

Gastric Bypass Surgery Risks

Gastric Bypass Surgery Risks - Bariatric Fusion

Are you thinking about gastric bypass surgery, or currently in the pre-op evaluation process? If so, it’s essential to understand all aspects of gastric bypass surgery, even the risks.

This article will help you prepare for the possible risks of gastric bypass surgery and how to address them.*

What This Article Covers:

Gastric Bypass Surgery Risks

Are you concerned about the potential risks of gastric bypass surgery? As with any surgery, it is important to weigh the possible downsides against the benefits.

The possible risks associated with gastric bypass surgery can vary in severity from minor inconveniences to potentially life-threatening complications.

Some of the potential risks and complications are short-term and resolve themselves, but others can cause gastric bypass complications years later.

Knowledge is power. It’s important to be fully prepared for any operation, including metabolic and bariatric surgery (MBS).

In this article, we will discuss the most common gastric bypass side effects to help you to make informed decisions as you prepare for the surgery.

The Mechanisms of Gastric Bypass Surgery

There are different types of weight loss surgeries currently available. It’s common to be confused about how they all work.

Gastric bypass surgery is a form of weight loss surgery that can enhance weight loss efforts in individuals suffering from obesity. As you probably already know, gastric bypass surgery is a weight loss surgery performed to help those who are obese.

Gastric bypass surgery aids in weight loss by altering the way your small intestine and stomach are able to process food.

First, the stomach is made into a smaller pouch so that food intake is restricted, resulting in less calorie consumption.

Next, the small intestine is re-routed and connected to the smaller stomach pouch. This bypasses part of the stomach and small intestine to prevent calories from being absorbed.

The mechanism of bariatric surgery procedures are important to understand so you can understand the risks and make the best decisions for you.

Potential Risks of Gastric Bypass Surgery

There are several risks involved with gastric bypass surgery. Here are a few of the most common ones, and ways you can help combat the likelihood of experiencing them.

Blood Clots

It’s possible for blood clots to form after laparoscopic gastric bypass. These blood clots most commonly appear in your lower legs as a deep vein thrombosis, but can also present as pulmonary embolisms.

Luckily, this risk can be mitigated by taking blood-thinning medications prescribed by your bariatric surgeon before and after your surgery. Discuss any known blood clotting conditions or concerns with your bariatric surgeon and healthcare team before surgery.


Gastric bypass surgery may also lead to certain types of infections, including wounds, pneumonia, bladder infections, and deep abdominal infections.

Wounds and abdominal infections are usually caused by bacteria and fluid build-up around the incision sites.

A bladder infection is possible when a urinary catheter is used to manage the build-up of urine during the bariatric procedure. It is usually left in place overnight and can lead to bacterial build-up and infection.

Fortunately, most of these health problems can be treated with the use of antibiotics. This is why follow-up appointments and consistent contact with your bariatric healthcare team are important.

Internal Bleeding

During surgery, it is necessary for surgeons to cut through blood vessels when making the “new” stomach and re-routing the small intestine.

Although these blood vessels are stitched up again afterward, some may continue to bleed around the abdomen. Internal bleeding is a rare occurrence, happening to roughly 3% of patients after surgery. (1)

Gastrointestinal bleeding is another risk after gastric bypass. This happens when bleeding occurs anywhere along the gastrointestinal tract and may lead to vomiting blood.

There’s nothing that can necessarily be done to avoid this risk, but it can be treated and managed through endoscopy or surgery in more serious cases.

Dumping Syndrome After Bariatric Surgery

There’s also a risk of a digestive issue called “dumping syndrome.” This happens when food passes too quickly from the stomach to the intestine without being properly digested.

As a result of this quickened digestion, you may experience side effects such as diarrhea, lightheadedness, abdominal pain, sweating, increased heart rate, and nausea.

Dumping syndrome often occurs when you eat high sugar and/or high-fat foods. To avoid this common gastric bypass problem, you can make small adjustments to your eating habits.

To lower your risk of dumping syndrome, focus on eating smaller meals, consuming protein first, avoiding high-sugar and high-fat foods, and refraining from drinking liquids during your meals.

Stomach Ulcers

Gastric bypass surgery may also cause stomach ulcers. Ulcers are painful sores that form in your stomach or intestinal lining.

Symptoms of a stomach ulcer include excessive pain after gastric bypass surgery, vomiting, nausea, or difficulty swallowing.

Most stomach ulcers are treated with medication prescribed by your healthcare provider.


Hernias occur when an organ or tissue protrudes through a weak spot in the surrounding muscle or tissue. Since gastric bypass consists of cutting through tissue and re-routing organs, weak spots can develop, and hernias can form as a result.

Internal hernias after gastric bypass are quite serious and can be a gastric bypass long-term side effect and risk.

There is nothing that can be done to prevent a hernia. Still, they can usually be managed and treated with a laparoscopic procedure, which allows for reduction and closure of the defect.

Anastomotic Stricture

An anastomotic stricture (also known as stenosis) is when the connection between the new stomach pouch and intestine starts to narrow.

The risk of anastomotic stricture or stenosis occurs in approximately 5 to 10% of people who have undergone roux-en-y gastric bypass surgery. (2)

With a laparoscopic gastric bypass, your stomach decreases in size, and anatomical changes are made. During the healing process, there are several factors that can cause stricture, like scarring.

The narrowing of the connection site between the stomach and the intestine results in decreased passage of food, nausea, reflux, and vomiting.

Since the formation of scar tissue after the operation is inevitable, anastomotic stricture is a high risk. However, it can be treated with endoscopy to dilate the stricture and increase the size of the passageway.

Anastomotic Leakage

An anastomotic leak can occur in 0.5 to 5% of people who have undergone gastric bypass surgery and can occur anywhere from 3 days to several weeks post-surgery. (3)

As explained earlier, the mechanism of a gastric bypass works by connecting part of the small intestine to the new stomach pouch.

This connection is called anastomosis, and there is a risk that this anastomosis could leak partially digested food and digestive juices into the abdominal cavity.

Anastomotic leakage is normally treated through antibiotics, an intravenous line, or surgical procedures.

Gastric Bypass Bowel Obstruction

After joining the stomach pouch and small intestine together in a gastric bypass, adhesions can occur.

Adhesions are bands of scar tissue that form where the connections have been created. This causes the bowel to become kinked around the adhesion, increasing the risk of blockage.

This doesn’t happen in all cases and is not a risk that can be preemptively prevented. However, this risk can be potentially life-threatening in severe cases and needs to be corrected through surgical procedures.

Mineral, Vitamin, and Protein Deficiencies

One of the most common risks after gastric bypass is vitamin, protein, and mineral deficiencies.

After gastric bypass surgery, your stomach cannot handle a large amount of food. This food restriction results in fewer nutrients being consumed, including protein, which becomes a priority after a bariatric procedure.

Malnutrition can also occur due to partial bypassing of the small intestine, further increasing the risk of vitamin and mineral deficiencies.

For this reason, it is crucial to choose nutrient-dense foods, to eat protein first, and adhere to any supplement recommendations made by your bariatric surgeon.*

It is generally recommended to supplement your post-surgery diet with a post-bariatric multivitamin and bariatric whey protein to keep your body nourished.* Be sure to discuss your supplement plan with your bariatric healthcare team.

bariatric multivitamin

Hair Loss

Hair loss after gastric bypass is another common risk following bariatric procedures.

This happens due to drinking less water, malabsorption of vitamins and proteins, and the stress of surgery itself.

You can mitigate this risk by ensuring that you are getting enough nutrients through a daily bariatric multivitamin, protein supplements, and adequate fluid intake.* (Just be sure not to drink fluids with your meals!)

Depression After Bariatric Surgery

There is a possible risk of depression after bariatric surgery. While this is not a surgical or nutritional risk, it can be just as serious.

Depression after gastric bypass or sleeve gastrectomy surgery can occur for various reasons, like not seeing the expected weight loss right away.

Many patients expect the journey after gastric bypass to be easy and for the weight to fall right off. However, you still have to put in the work to get results. Without exercise and proper nutrition, it’s easy to fall short of expected goals and to feel depressed as a result.

Even if you’re doing all the right things, it’s possible to experience depression as a result of bariatric surgery. Try working with a qualified healthcare provider to process your thoughts and feelings.

Another good reason to exercise: It releases endorphins, which improve your mood!

Kidney Stones

The risk of kidney stones after bariatric surgery is fairly high. This is related to a change in urine, which contains higher amounts of oxalates after gastric bypass.

Oxalates are a common cause of kidney stones and can be naturally absorbed by the GI tract. However, the GI tract changes that result from gastric bypass surgery can alter the absorption of these oxalates.

As a result, patients with gastric bypass are at a much higher risk for the formation of kidney stones.

Fortunately, there are ways to decrease this risk, including drinking lots of water, decreasing consumption of oxalate-containing foods (such as beetroot, spinach, chocolate, and nuts), and reducing your sodium intake.


Short-term and long-term dehydration is another risk of gastric bypass.

The risk of short-term dehydration is heightened by the swelling that occurs post-surgery. Swelling can further reduce the stomach size and cause pain when ingesting fluids. The combination of reduced stomach size due to surgery and swelling can lead to a deficient intake of water.

Dehydration can also be a long-term risk. The reduced stomach size plays a role, as well as the recommendation to not drink fluids 30 minutes before and after meals.

Side effects and symptoms of dehydration include excessive thirst, dark-colored urine, dry mouth, and lightheadedness.

The risk of dehydration post gastric bypass can be mitigated by slowly consuming adequate fluids throughout the day.

Weight Gain

Although it is not often discussed, it is possible to gain weight after gastric bypass.

For the first few months after surgery, the weight may come off fairly easily. However, after about six months or longer, weight loss starts to plateau.

Your body starts to find a “new normal” in terms of weight, and your portion sizes also start to become bigger than what they were immediately following surgery.

This can result in regaining some of the weight you lost from surgery. However, most people just gain a few pounds – they don’t return to their pre-surgery weight.

That being said, it is important to adhere to an exercise regimen, and to continue making smart dietary choices for the rest of your life.


While there are a number of risks associated with gastric bypass, simply being aware of potential side effects can help to avoid and manage most potential complications.

It is important to remember that bariatric surgery is only a tool to enhance weight loss, not the solution itself. It’s important to take good care of yourself to maintain health and achieve weight loss, like staying active, hydrated, and nourished.

Be sure to stay in contact with your healthcare provider, attend follow-up appointments, and undergo regular blood work to support your ongoing good health.

If you are looking for bariatric-specific supplements, check out Bariatric Fusion’s line of multivitamins, protein powders, and other supplements designed by our team of bariatric experts.*

Click here to shop Bariatric Supplements

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This blog is for information and education purposes only. This information is not intended to substitute professional medical advice, diagnosis, or treatment. Please consult with your healthcare provider with any questions in regards to a medical condition. A qualified healthcare professional can best assist you in deciding whether a dietary supplement is suitable based on your individual needs.

*These statements have not been evaluated by the Food and Drug Administration (FDA). These products are not intended to diagnose, treat, cure, or prevent any disease.

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