Iron Deficiency After Gastric Bypass Surgery

Iron deficiency and anemia are common after a gastric bypass or other weight-loss surgery, especially in women. In fact, iron deficiency can occur in more than half of women who are premenopausal who have this surgery.

Iron deficiency is a side effect that happens because of the changes made during the surgery. Most of the iron from foods like meats, legumes, and iron-fortified grains is absorbed in the first part of the small intestine called the duodenum. But after a gastric bypass procedure, food bypasses this part of the body before minerals and vitamins can be absorbed. This can lead to iron deficiency and other nutrition problems.

The Roux-en-Y gastric bypass, or RGBY, is the most common type of gastric bypass. Studies say that the amount of iron in a standard multivitamin (18 mg) may not be enough to prevent anemia if you have this kind of surgery.


Iron has many important roles in the body. It’s important for the health of your hair, skin, and nails. It also helps create hemoglobin, the substance inside red blood cells that carries oxygen throughout the body. When you are anemic because of iron deficiency, you may notice:

  • Lack of energy

  • Weakness

  • Headache

  • Rapid heartbeat

  • Hair loss

  • Brittle nails

  • Pale or yellow skin

  • Shortness of breath

  • Chest pain

  • Strange pounding sensation in your ears

  • Craving for ice or clay (known as pagophagia)


Your doctor will take note of any of the above symptoms. He or she will also order blood tests to find out if you have iron deficiency or anemia. In its early stages, iron deficiency begins to use up the stores of iron in your body. This can be seen by testing your levels of ferritin, a protein that stores iron in the body. If your ferritin levels are low, iron is likely low.

If the iron deficiency has advanced to iron deficiency anemia, a complete blood count will show some problems. These include low hemoglobin, lower numbers of red blood cells, and smaller red blood cell size.

For men or postmenopausal women, iron deficiency anemia is usually not related to the gastric bypass surgery. Your doctor will need to be certain that you are not anemic from blood loss elsewhere, such as from the intestine. He or she may suggest a colonoscopy to look for a source of blood loss from the large intestine. 


Many people can raise their iron levels by making some changes to their diet. If your iron deficiency is related to a gastric bypass procedure, your doctor probably will prescribe iron supplements. This extra iron should come from a prescription from your doctor, not from an over-the-counter (OTC) supplement you pick yourself. The exception to this is if your doctor recommends a specific OTC iron product for you.

If you are a teen boy or girl or a woman of childbearing age, you may need two multivitamins plus 50 to 100 mg of elemental iron each day, according to recent guidelines from the American Society for Metabolic and Bariatric Surgery. The organization also recommends vitamin C supplements, among others, to increase the amount of iron your body is able to absorb. Your doctor will determine the right amount of iron for you.

Iron supplement can cause side effects. Many people have constipation and nausea, among other problems.

For some people, usually women with heavy menstrual periods, supplements aren’t enough. They may need iron through an IV, blood transfusions, or even surgical revision of the bypass to raise the amount of iron absorbed.


You should have a thorough blood workup before weight-loss surgery to find out any existing vitamin or mineral deficiencies, such as iron, vitamin B12, and folate. Studies suggest that treating these deficiencies before your operation will improve your outcome and quality of life after surgery.

After gastric bypass surgery, you will need to monitor the level of iron and other nutrients for the rest of your life. You can develop iron deficiency and anemia years and even decades after your gastric bypass surgery. According to guidelines from the ASMBS, your doctor should measure your serum iron six months after weight-loss surgery and at least once a year after that, along with a complete blood count.

Red meat, poultry, seafood, leafy greens, legumes, iron-fortified grains, and other iron-fortified foods are all good sources of iron. Drinking more than 16 to 24 ounces of milk each day may decrease how much iron you absorb. But remember that dietary measures alone may not be enough to prevent or correct an iron deficiency related to a gastric bypass procedure. Work with your doctor to find the right iron supplement plan for you.