Bariatric Surgery FAQ

Low Blood Sugar After Gastric Bypass Surgery

Low Blood Sugar After Gastric Bypass Surgery - Bariatric Fusion

Bariatric surgery results in weight loss and resolution or improvements in type 2 diabetes, high blood pressure and high cholesterol.1 So, why might low blood sugar still occur?

Low blood sugar can be a complication after gastric bypass surgery. Severe low blood sugar where hospitalization might be warranted is not as common in patients.

The good news is that it is possible to control and monitor this problem. There are signs and symptoms to look for so that you are prepared if you experience this complication.

This article covers what you need to be aware of as a bariatric patient regarding low blood glucose. We’ve included some helpful tips for dealing with and avoiding the problem. We discuss what causes hypoglycemia and some of the symptoms to watch out for.

What This Article Covers:

The Causes of Low Blood Sugar After Gastric Bypass Surgery

After a gastric bypass, also called Roux-en-Y bariatric surgery, there are quite a few alterations made to the digestive tract. The way your body digests food is also different. Low blood sugar or reactive hypoglycemia can develop for various reasons, including:

  • Drinking alcohol
  • Not eating regular meals
  • Eating food or beverages high in simple carbohydrates or sugar
  • Dumping syndrome

The changes of gastric bypass can cause excess insulin production. Eating certain foods can trigger the release of hormones to cause a rapid decline in glucose. Exercise can also have an effect on blood sugar levels.

When you skip meals, there is an imbalance in food intake and insulin production. You may feel light-headed, tired, dizzy, or your mood may change.

Reactive hypoglycemia is a little different. It can happen after you have eaten. It may happen after you’ve eaten something high in sugar or refined carbohydrates.

Refined carbohydrates can include added sugars and refined grains that are stripped of nutrients. These are foods like pastries, candy, soft drinks, fruit juices, muffins, pasta, and hidden sugar in many condiments we use, such as tomato sauce and salad dressings. These types of foods and beverages may be called high glycemic index options because they spike blood sugar and lead to a drop.

This can also be an effect of dumping syndrome when high sugar food sources are consumed and enter the small intestine too quickly. An excessive amount of insulin is secreted, leading to low blood sugar as well.

Symptoms of Low Blood Sugar After Gastric Bypass Surgery

The symptoms can include:

  • shaky
  • dizzy
  • weak
  • sweating
  • hunger
  • increased heart rate
  • confusion
  • mood swings
  • headache

Reactive hypoglycemia can happen within a few hours after a meal or snack. People can see symptoms of dumping syndrome anywhere from 10 minutes to 3 hours after eating.

If you feel you are having low blood sugar, you should check with a glucose monitor. If it is too low, you may need to treat it with 15 grams of a fast acting carbohydrate, or as directed by your healthcare provider.

This can be a very serious matter and bariatric patients should be cautious.

What Happens When You Have Low Blood Sugar Often?

It is extremely important to maintain normal blood sugar levels. If these health problems continue happening in the long-term, your body may no longer be able to provide signs and symptoms of altered blood sugar levels. This can lead to severe, life-threatening reactions.

You might have some unexpected symptoms of hypoglycemia that seem unrelated to your diet. This includes finding it difficult to sleep at night, slurred speech, clumsiness, bladder problems, and persistent infections.

These can be signs of a more serious problem. It is always recommended to consult with your healthcare provider about health concerns you might have.

Gastric bypass may resolve diabetes. If symptoms only improve, it is important to remember your glucose monitor and healthful maintenance of your blood sugar levels. Medications may be adjusted or even stopped. Even if bariatric surgery does not resolve type 2 diabetes, the improvements can still significantly change your life. Bariatric surgery and diabetes can be managed.

How to Prevent Hypoglycemia in Bariatric Patients

After bariatric surgery, lifestyle change will promote desired weight loss and maintain health in the long-run. Your healthcare provider will be able to best direct you in how to handle your specific case of low blood sugar. Some changes that may prevent low blood sugar and other related complications are listed below.

Follow a Meal Plan

meal plan

Having a planned healthy food schedule. Eating regular meals every 2-3 hours will help to control blood sugar levels.

After gastric bypass surgery, diet plans will usually have 3 healthy meals and 2 or 3 small healthy snacks. They will be spread over the whole day and spaced 2 to 3 hours apart. This should be provided to you by your dietitian or healthcare team.

Many patients are assigned a 1000-calorie bariatric diet plan by the time they are eating 6 months after a gastric bypass.

For example, you can split this up into 3 healthy meals of about 300 calories each. Then, add 2 snacks of 50 calories each.

Even if you do not have an appetite, make sure you are eating something at scheduled times. Don’t skip a meal. Instead, try something you can drink that is nutritious enough to count as a healthy snack or light meal. This would include something like a high protein meal replacement shake.

Make sure the foods you choose are all on the gastric bypass foods list and you don’t skip any of your meals.

Limit or Avoid Caffeine and Alcohol Intake

Limit or Avoid Caffeine and Alcohol Intake

Be careful when drinking alcohol after gastric bypass surgery. Alcoholic beverages can contain high sugar and can also decrease the liver's ability to release glucose. This can lead to unhealthy changes in blood sugar levels.

Caffeine can be associated with insulin resistance. This is when glucose and insulin build up in the blood. Looking at the bigger picture, insulin can play a role in weight control in regards to fat storage and appetite.

Find bariatric recipes that incorporate your favorite foods after weight loss surgery. Following a bariatric diet and lifestyle is the best way to maintain weight loss and health after bariatric surgery.

Eat Protein with Each Meal and Snack

Proteins and healthy fats should be a priority. You will pair protein and healthy fats with other macronutrients, like carbohydrates.

Instead of sugar and refined carbohydrates, choose complex carbohydrates. Pairing complex carbohydrates, such as whole grains, vegetables, and beans, with a protein will slow the release of glucose. These low glycemic index foods help release sugar into your system gradually.

Also, make sure to eat protein first at each meal. After, you can have a complex carb to protect your blood sugar levels until the next meal. Protein is of the highest importance after bariatric surgery in order to maintain and build muscle to support your metabolism.

For example, start with your skinless chicken breast and salad at lunchtime. Then, you would move on to your portion of steamed sweet potato. Remember to only consume portions and food options that are listed by your dietitian or doctor.

You can use specialized bariatric dinnerware to help you dish up the right portions, measure your food, and eat slowly.

Consume Nutrient-Dense Foods

For snacks and meals you should be consuming nutrient-dense foods that provide you with a wide variety of micro and macronutrients. You want to avoid options that provide empty calories.

This refers to foods and beverages that are high in calories, but provide little to no nutritional value. This would include foods like cookies and some snack bars/granola bars.

Nutrient-dense foods should also keep you fuller for a longer period of time. If you are hungry in between meals, choose a small snack of almonds or plain yogurt. When it is time for your next meal, you will be less likely to grab whatever is in your path because you are hungry. This will lead to healthier choices and better blood sugar control when you can plan and think about what you're eating.

Keep Track of Blood Sugar Levels

You may have experienced reactive hypoglycemia or dumping syndrome before. There may even be a history of diabetes in your family. In that case, you can purchase a glucometer to check your glucose levels daily.

You don’t have to have diabetes to use a glucose monitor. It can give you useful information about your body.

You can start testing yourself at any time, but it’s best to start testing about 2 hours after a meal. Also test after an overnight fast or 8-hour window.

The results can be life-saving when your blood sugar is high or low.

Using a Blood Glucose Monitor or Glucometer as a Bariatric Patient

Using a Blood Glucose Monitor or Glucometer as a Bariatric Patient

Normally, a blood sugar is about 140 mg/dL when tested 1-3 hours after eating something. This can be measured differently based on the meter you are using. After fasting, normal is about 99 mg/dL.2

Generally, a person wouldn’t want their blood sugar to vary significantly from these levels. However, as a bariatric patient, your normal glucose levels can be slightly different from this, especially if you have diabetes or are prediabetic.

Prediabetes means that you at a higher risk of developing type 2 diabetes if you do not make lifestyle changes. It has been shown that up to 70% of individuals with prediabetes develop type 2 diabetes.3 It is likely for those who qualify for bariatric surgery to be prediabetic secondary to obesity.

Consult with your healthcare provider regarding your blood sugar levels throughout the day. The blood glucose monitor will immediately tell you your blood levels and if you need to take action before things become serious.

Fixing the problem often just means having a healthy snack immediately and then making sure you have every meal on time for the rest of the day. It can also confirm that something you ate is what’s causing a problem.

Always reach out to your healthcare provider regarding medical advice on blood sugar levels and how to treat the issue in the moment.

Take Supplements

Take Supplements

Hypoglycemia can also be seen years after surgery. There hasn't been a correlation found between the severity of hypoglycemia and micronutrient supplementation. However, years after surgery, patients have been found to no longer take their bariatric supplements.

Supplements are essential for life after any bariatric surgery. If bariatric patients are self-treating hypoglycemia by limiting certain foods that might trigger a reaction, it is important to ensure you are continuing to take your bariatric supplements.4

Restricting, avoiding, and malabsorption of different foods can diminish a number of vitamins and minerals. It is extremely important to make sure you continue to take bariatric supplements for life to maintain good health.*

Did you find our blog helpful? Then consider checking:


1. Goldfine AB et al. Obesity (Silver Spring). 2016;24(6):1210–1211.

2. Centers for Disease Control and Prevention. 2023. Accessed from

3. Tabák AG et al. Lancet. 2012;379(9833):2279–2290.

4. Suhl E et al. Surg Obes Relat Dis. 2017;13(5):888–896.

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

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 physician or another qualified health 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.

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