Most people experience at least a few side effects after bariatric surgery. Some are part of the normal healing process. Others are signs that something needs medical attention. Knowing the difference helps you recover faster and stay safe.
This page covers the most common side effects and how to manage them, with normal symptoms clearly separated from red flags. For a complete list of warning signs that require immediate medical attention, visit the Warning Signs That Require Medical Attention page.
Nausea and Vomiting
Nausea is one of the most common side effects in the first few weeks after surgery. It can be triggered by medications, anesthesia, drinking fluids too quickly, eating too much or too fast, and even strong smells. For most patients, nausea improves significantly within the first week.
How to manage it. Sip fluids slowly instead of gulping. Avoid strong cooking smells while your stomach is sensitive. Stick to your surgeon's dietary guidelines. If nausea continues, your surgeon may recommend an anti-nausea medication. Do not take any over-the-counter nausea medicine without checking with your care team.
Watch for: If you cannot keep any fluids down for more than a few hours, call your surgeon. Repeated vomiting, especially if the vomit is dark or contains blood, is not normal. Seek medical attention immediately.
Fatigue and Low Energy
Fatigue is nearly universal during the first two weeks. Your body is healing from a major procedure while taking in a fraction of the calories you are used to. It is normal to feel tired.
How to manage it. Rest is part of your recovery. Nap when you need to. Focus on hydration and hitting your protein goals, because dehydration and low protein both make fatigue worse. Short, gentle walks help with circulation. Your energy will return gradually over the first several weeks.
Watch for: Extreme fatigue that does not improve after two weeks, or fatigue that gets worse, should be discussed with your surgeon. It could be a sign of dehydration or a nutritional deficiency.
Shoulder Pain (Laparoscopic Gas)
If you had laparoscopic surgery, you may feel sharp pain in your shoulder or upper back. This is referred pain from the gas used to inflate your abdomen. The gas pushes against your diaphragm, which shares nerves with your shoulder.
How to manage it. Walking is the best remedy. Movement helps the gas dissipate more quickly. A heating pad on your shoulder can also help. The pain usually resolves within a few days.
Watch for: Shoulder pain that lasts longer than a week, or pain that comes with shortness of breath or chest pain, could be a sign of a blood clot. Go to the emergency room.
Constipation
Constipation is common after bariatric surgery. Pain medications slow down your digestive system. Dehydration makes it worse. Reduced food intake also reduces the bulk moving through your intestines.
How to manage it. Prioritize hydration. Sip water consistently throughout the day. If your surgeon has cleared you, a gentle stool softener like docusate can help. Do not use stimulant laxatives unless your surgeon tells you to. Walking and gentle movement also help.
Watch for: If you have not had a bowel movement in three or more days and are experiencing abdominal pain or bloating, call your surgeon.
Gas and Bloating
Gas and bloating are very common in the early weeks. Your digestive system is learning to process food in a new way. It usually improves as your body adjusts.
How to manage it. Do not use straws or chew gum. Both cause you to swallow air. Take small sips of fluids instead of gulping. When you advance to solid foods, chew thoroughly and eat slowly. Introduce new foods one at a time to identify what bothers you.
Watch for: Severe bloating with abdominal pain, nausea, or vomiting could be a sign of a blockage. Call your surgeon.
Body Temperature Changes
Many patients feel cold in the weeks after surgery. Others experience night sweats. Both are normal. Hormonal shifts, reduced calorie intake, and loss of insulating body fat all affect temperature regulation.
How to manage it. Dress in layers. For night sweats, use breathable cotton sheets. These symptoms usually resolve on their own as your body stabilizes.
Watch for: A fever over 101 degrees Fahrenheit is not temperature dysregulation. It is a potential sign of infection. Call your surgeon.
Emotional Ups and Downs
Bariatric surgery is not just a physical procedure. Hormonal changes affect your mood. Your body is under stress from healing. The reality of a new relationship with food can feel overwhelming. Many patients feel excited one day and tearful the next. This is normal.
How to manage it. Give yourself permission to feel what you feel. Talk to your support system. Many patients find bariatric support groups helpful because they are surrounded by people who understand. If you have a history of depression or anxiety, make sure your mental health provider is part of your care team.
Watch for: If your mood does not improve after the first few weeks, or if you feel hopeless, withdrawn, or have thoughts of hurting yourself, get help immediately. Call your surgeon, your doctor, or a mental health crisis line.
Hair Thinning
Hair thinning is one of the most distressing side effects for many patients, especially women. It usually starts around three to six months after surgery and can last several months. The cause is rapid weight loss, reduced calorie intake, and the physical stress of surgery. This type of hair loss, called telogen effluvium, is temporary.
How to manage it. Meet your protein and vitamin goals every day. Hair needs protein, iron, zinc, and biotin to grow. Take your supplements consistently. Avoid harsh chemical treatments and tight hairstyles. The hair will grow back once your weight stabilizes and your nutrition is adequate.
Watch for: If hair loss leaves bald patches or continues beyond a year, talk to your surgeon. You may need blood work to check for nutritional deficiencies.
Dumping Syndrome
Dumping syndrome is a reaction that can occur after gastric bypass and some other procedures. It happens when food, especially sugar or high-fat food, moves too quickly from your stomach into your small intestine. Symptoms include nausea, sweating, rapid heart rate, diarrhea, dizziness, and feeling faint.
Dumping syndrome is not a complication. It is a built-in deterrent. It is your body's way of telling you that you ate something you should not have. Many patients find it helpful because it reinforces the dietary rules.
How to manage it. The best treatment is prevention. Avoid sugary foods, high-fat foods, and liquid calories. Eat small meals. Do not drink with your meals. Wait 30 minutes after eating before drinking. If you experience dumping, lie down until the symptoms pass and sip water slowly. The episode usually resolves within 30 to 60 minutes.
Watch for: If dumping happens frequently, work with your dietitian to identify trigger foods. If an episode causes severe dehydration, call your surgeon.
Changes in Taste and Smell
Many patients report that their sense of taste changes after surgery. Foods they used to love may taste different or unappealing. Some develop an aversion to meat, eggs, or other high-protein foods. These changes are related to hormonal shifts and possible zinc deficiency.
How to manage it. Experiment with different protein sources. If meat does not appeal to you, try Greek yogurt, cottage cheese, tofu, fish, or plant-based protein shakes. Ask your surgeon to check your zinc levels if the problem persists.
Watch for: Taste changes that cause you to eat significantly less or avoid protein entirely. Talk to your dietitian for help finding protein sources you can tolerate.
Dizziness and Lightheadedness
Dizziness is common in the first few weeks. It is usually caused by dehydration, low blood sugar, or low blood pressure. Your body is adjusting to a much lower calorie intake, and your blood pressure may drop as you lose weight quickly.
How to manage it. Stay hydrated and sip water throughout the day. Do not skip meals. Stand up slowly, especially when getting out of bed. If you feel dizzy, sit or lie down until it passes.
Watch for: If dizziness comes with chest pain, shortness of breath, or a racing heart, seek medical attention. If you faint, call your surgeon.
Red Flags: When Normal Is Not Normal
Many of the side effects above are normal and expected. But some symptoms are never normal after bariatric surgery. They are red flags that require immediate medical attention. Knowing the difference can save your life.
These symptoms are not part of normal recovery:
- Severe abdominal pain that gets worse or does not improve with rest. Some soreness is normal. Sharp, stabbing, or persistent pain is not.
- Fever over 101 degrees Fahrenheit. A low-grade temperature can be normal. A fever above 101 is not.
- Inability to keep fluids down for more than a few hours. Dehydration is a leading cause of hospital readmission after bariatric surgery.
- Signs of infection at incision sites: redness, swelling, warmth, drainage, or a foul smell.
- Shortness of breath, chest pain, or a racing heart. These could be signs of a blood clot or pulmonary embolism. They are medical emergencies.
- Pain or swelling in one leg more than the other. This could be a deep vein thrombosis (DVT).
- Vomiting blood or material that looks like coffee grounds. This indicates bleeding in the digestive tract.
- Feeling confused, faint, or unable to stay awake.
If you experience any of these symptoms, do not wait. Call your surgeon or go to the nearest emergency room. It is always better to be checked and find out nothing is wrong than to delay treatment for a real problem.
For a complete guide to red flag symptoms, visit the Warning Signs That Require Medical Attention page.
When to Talk to Your Care Team
You do not need to wait for a red flag to call your surgeon. Your care team is there to help. Call if you are unsure whether a symptom is normal, cannot keep fluids down, have uncontrolled pain, show signs of dehydration (dark urine, dry mouth, dizziness), are struggling with protein or fluid goals, are concerned about emotional changes, or have questions about your diet stage.
Your bariatric team is your partner in recovery. They would rather you call 10 times with small questions than avoid calling until something becomes serious. For a deeper look at recovery timelines, see the What to Expect in the First Year of Weight Loss page.
Related Reading
- Warning Signs That Require Medical Attention: complete guide to red flag symptoms.
- Nutritional Changes After Surgery: how your body absorbs nutrients differently.
- Why Some Foods Are Off Limits After Surgery: dumping syndrome, sugar, and fat tolerance.
- What to Expect in the First Year of Weight Loss: recovery timeline and milestones.
- Managing Cravings and Emotional Eating: strategies for the emotional side of the journey.
- Hydration After Bariatric Surgery: why hydration matters and how to stay on track.
References
- Stenberg E, Szabo E, Agren G, et al. Early complications after laparoscopic gastric bypass surgery. Annals of Surgery. 2014;260(6):1040-1047.
- Chang SH, Stoll CR, Song J, et al. The effectiveness and risks of bariatric surgery: An updated systematic review and meta-analysis. JAMA Surgery. 2014;149(3):275-287.
- Mechanick JI, Apovian C, Brethauer S, et al. Clinical practice guidelines for the perioperative nutrition, metabolic, and nonsurgical support of patients undergoing bariatric procedures. Endocrine Practice. 2019;25(Suppl 1):1-75.
- Parrott J, Frank L, Rabena R, et al. American Society for Metabolic and Bariatric Surgery integrated health nutritional guidelines for the surgical weight loss patient. Surgery for Obesity and Related Diseases. 2017;13(5):727-741.
- Sherf Dagan S, Goldenshluger A, Globus I, et al. Nutritional recommendations for adult bariatric surgery patients: clinical practice. Advances in Nutrition. 2017;8(2):382-394.