Risks of Bariatric Surgery: Anemia

What is anemia after bariatric surgery?

Anemia is when your blood has lower levels of red blood cells. Or it may be that your red blood cells don’t have enough hemoglobin. Hemoglobin is a protein that carries oxygen through the body in the blood. Anemia may occur after weight-loss surgery (bariatric surgery).

What causes anemia after bariatric surgery?

Anemia can be caused by:

  • Getting too little iron. After bariatric surgery, your body may have trouble digesting red meat. This can make you more likely to have anemia. Red meat can be a big source of iron in a person’s diet. This problem is more likely to occur after a Roux-en-Y gastric bypass (RYGB).

  • Not absorbing enough iron. This can occur after bariatric surgery. Your body needs iron and specific nutrients to make hemoglobin and healthy red blood cells. Weight-loss surgery can also reduce the level of stomach acids that break down foods. That can also lead to nutrition-related anemia. With the gastric bypass, the intestines are rerouted to bypass the duodenum and upper jejunum. These are the parts of the small intestine where most of the iron and calcium in your food are absorbed. This makes it harder for your body to absorb iron and other nutrients.

  • Bleeding in your digestive system. Some people develop an ulcer after a gastric bypass. Chronic blood loss from the ulcer can cause anemia. 

  • Having low levels of other nutrients. Not getting enough folic acid and vitamin B-12 can also cause anemia. Vitamin and mineral problems are common in people after surgery. Weight-loss surgery limits the amount and the types of food you can eat.

Who is at risk for anemia after bariatric surgery?

Teens, women who still have their periods, and pregnant women are at higher risk for anemia after bariatric surgery. Some people may be anemic even before they have bariatric surgery. Chronic inflammation caused by obesity may lead to anemia by affecting the immune system. In these cases, the surgery alone may not have caused the anemia.

What are the symptoms of anemia?

Anemia can cause symptoms such as:

  • Tiredness (fatigue) or lack of energy

  • Trouble exercising

  • Chest pains, especially if you have heart disease

  • Cold feet and hands

  • Feeling short of breath

  • Headaches

  • Dizziness

  • Unusually pale skin

How is anemia diagnosed?

You will likely need tests to check for anemia. A blood test can check your red blood cell and hemoglobin levels. Your healthcare provider may want to check your stool for small amounts of hidden blood. If there is blood in your stool, you may need a colonoscopy, endoscopy, or other imaging tests. These are to check for bleeding in your digestive system that may be causing hidden blood loss.

How is anemia treated?

People with severe anemia may need a blood transfusion to replenish oxygen-rich red blood cells. You’ll also need to make sure your diet contains iron-rich foods and vitamins, and minerals. Your healthcare provider will check your blood every so often. You may also need supplemental iron or vitamin B-12. Your healthcare provider may prescribe them for you. 

Can anemia be prevented after bariatric surgery?

After bariatric surgery, your healthcare provider will need to check you for anemia for the rest of your life. This is because anemia may not develop until many years after the surgery. You’ll have regular blood tests 6 months after weight-loss surgery and at least once a year after that.

You may need to work with a nutritionist or registered dietitian to watch your diet after surgery. It's important to take daily vitamin and mineral supplements after bariatric surgery to prevent anemia and other nutritional problems. It's also important to eat iron-rich foods such as:

  • Meat, especially red meat, if possible

  • Lentils, peas, and beans

  • Dried prunes, apricots, raisins, and other fruits

  • Cereals and breads fortified with iron

  • Dark, leafy green vegetables like spinach

  • Tofu

  • Prune juice

Vitamin C from foods and supplements can help your body absorb iron. Make sure you take iron supplements with foods rich in vitamin C, such as citrus fruits. Calcium supplements and antacids can decrease iron absorption. Try to give a 1- to 2-hour period between taking calcium and iron supplements.

If you had a gastric bypass, the amount of iron in a standard multivitamin—about 18 mg—may not be enough to prevent anemia. Your healthcare provider may recommend you take more iron.

If you are a teen or are menstruating, you may need extra iron no matter what type of weight-loss surgery you had. Your healthcare provider will do blood tests to help figure out your iron supplement dose. This is important because too much iron can be as bad for you as too little iron.

Key points about anemia after bariatric surgery

  • Anemia is a common side effect of weight-loss surgery.

  • After bariatric surgery, your healthcare provider will need to check you for anemia for the rest of your life.

  • Weight-loss surgery changes the way your body absorbs vitamins and minerals from food.

  • Anemia can happen if you don't get enough iron or your body doesn't absorb enough of it.

  • Teens, women who still have their periods, and pregnant women are at higher risk of developing anemia after weight-loss surgery.

  • Your healthcare provider will most likely have you work with a nutritionist or registered dietitian to make sure you are getting enough vitamins, minerals, and iron-rich foods.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your healthcare provider tells you.

  • At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your healthcare provider gives you.

  • Know why a new medicine or treatment is prescribed and how it will help you. Also, know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your healthcare provider if you have questions.

Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Rajadurai Samnishanth
Online Medical Reviewer: Susan K. Dempsey-Walls RN
Date Last Reviewed: 2/1/2024
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