Infection, including in the stomach, abdomen (peritonitis), the cuts (incisions), the urinary tract or the lungs, as well as other locations

Leaks, blockage at a site where tissue is sewn or stapled together (anastomosis) or elsewhere due to adhesions, or bleeding. This will require more procedures or even another major surgery to fix.

Breathing problems, such as pneumonia or collapsed lung. This may require breathing help with a machine (ventilator) and other procedures, such as a chest tube.

Acid reflux, ulcers, or esophagitis 

Dumping syndrome (diarrhea, cramps, abdominal pain, and other gastrointestinal symptoms)

Kidney failure, possibly requiring dialysis on a short-term or long-term basis

Internal hernia, which needs surgery to fix

Small bowel blockage, which often requires surgery

Depressed mood or other psychological issues 

Blood clots in the legs that may travel to the lungs or heart and be life-threatening

Injury to the spleen. Sometimes the spleen needs to be removed, which can lead to problems with immunity.

Recurrent vomiting that needs a procedure to stop the problem

Development of a hernia at one of the incision sites (including internally) 

Problems from anesthesia, such as allergies and other reactions

Increased risk of fractures due to reduced bone mineral density

Stroke

Heart issues such as heart attacks and irregular heartbeats (arrhythmias)

Other rare but severe problems

Long-term nutritional issues, even when taking supplements. In some cases, supplements must be given by IV (intravenously) for absorption.

Fluid loss (dehydration) 

Death

After surgery, your body may not absorb all the nutrients it needs. This may make malnutrition, anemia, or vitamin and mineral deficiency more likely. Vitamin and mineral supplements are needed to prevent this.

Dehydration is more likely after surgery. You must drink enough liquids each day.

Gallstones may happen, and more surgery may be needed (for gallbladder removal and other procedures). 

You may fail to meet your weight-loss goals. Or you may gain weight after early weight loss.

Short-term hair loss is a common side effect of this surgery.

Lower tolerance of alcohol after surgery. For better healing, don't drink alcohol for the first 6 months after surgery. The surgery can also lead to metabolic changes. These can increase your sensitivity to even small amounts of alcohol.

Loose folds of skin are common after losing a lot of weight. Extra skin can be surgically removed when your weight has stabilized. But this may not be fully covered by your insurance. Also, many surgeries may be needed for the best results.

Depending on the specific bariatric procedure used, there is the potential for fertility and pregnancy issues. Pregnancy planning and contraception should be discussed before surgery. Oral contraceptives may be less effective in women who have had malabsorptive bariatric surgery.

It is recommended that pregnancy be postponed for 12 months following bariatric surgery. The purpose of this guideline is to optimize weight loss and decrease the risk of nutritional deficiencies for both the mother and the baby.

American Society for Metabolic and Bariatric Surgery at www.asmbs.org

National Heart, Lung, and Blood Institute Obesity Education Initiative at www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt