Colorectal cancer can cause bleeding from polyps in the digestive tract. This can lead to iron deficiency anemia. Oral and intravenous iron may help, but there may be some risks.

Persistent bleeding from polyps can lead to iron deficiency anemia in people with colorectal cancer.

Symptoms of anemia might not develop in mild cases. In cases of severe anemia, you may experience symptoms such as shortness of breath and chest pain.

If you have anemia with colorectal cancer, your doctor can provide you with information about the available treatments, including the possible benefits and risks.

Read on to learn more about the link between colorectal cancer and anemia, how to recognize symptoms, treatment options, and more.

Colorectal cancer may cause iron deficiency anemia because of bleeding from polyps in the digestive tract.

Colorectal cancer typically begins when polyps grow in the inner lining of the rectum or colon. Polyps are common and often benign. However, some types of polyps, such as adenomatous polyps, can develop into cancer.

In some cases, polyps can bleed in the digestive tract. You may notice blood in your stool, but this is not always the case.

If this bleeding happens often or persistently over time, it can lead to iron deficiency anemia. The body loses iron through bleeding, and it needs iron to make healthy red blood cells.

The iron deficiency means that the body cannot provide enough healthy red blood cells, and this can lead to symptoms of anemia.

A 2023 review suggests that anywhere from 30% to 75% of people with colorectal cancer.

The review also provides the following information:

  • 50% of people with colon cancer have anemia before surgery
  • 20% of people with rectal cancer have anemia before surgery.
  • 77% of people with colon cancer have anemia after surgery.
  • 66% of people with rectal cancer have anemia after surgery.

The occurrence of anemia after surgery may be due to blood loss during the procedure.

According to 2022 research, iron-deficient anemia may actually be underdiagnosed among people with colorectal cancer. This means that anemia with colorectal cancer may be more common than statistics currently suggest.

You may not experience symptoms of iron deficiency anemia if it’s mild or moderate. However, in severe cases, symptoms can include:

  • shortness of breath
  • tiredness
  • chest pain
  • fatigue
  • lightheadedness
  • dizziness
  • pale skin
  • cold hands and feet

If colon polyps are bleeding, you may experience rectal bleeding with bright red blood, or stool may look red or black. However, you may not notice any stool changes.

If you have colorectal cancer and your doctor suspects anemia, they will likely order a blood test.

This can include a complete blood count, as well as checking levels of hemoglobin and ferritin.

Oral or intravenous (IV) iron are possible treatments for people with anemia and colorectal cancer.

However, a 2018 article explains that iron may worsen the outlook for a person with a colorectal tumor. The article also suggests that oral iron does not absorb properly for people with colorectal cancer.

Your doctor will be able to provide more information about the possible benefits and risks of iron therapy to help manage anemia, as well as what dosage they recommend.

In general, without proper treatment, iron deficiency anemia can cause complications such as:

  • headache
  • fatigue
  • heart problems
  • restless legs syndrome (RLS)
  • complications during pregnancy
  • developmental delays during childhood
  • worsening of existing medical conditions

According to a 2021 review, iron deficiency anemia is independently associated with an increased risk of colorectal cancer recurrence and mortality.

Receiving treatment for anemia may help to reduce this risk. Your doctor can provide more information about the type of treatment they recommend and the possible benefits.

Iron deficiency anemia may develop with colorectal cancer due to colon polyps bleeding in the digestive tract. In severe cases, this can cause symptoms such as shortness of breath, tiredness, and chest pain.

Your doctor may order blood tests if they suspect anemia. After confirming the diagnosis, they can advise on a suitable treatment plan, which may include oral or IV iron.