Research shows that anemia and cancer are strongly connected. A significant number of people with cancer — between 30 and 90 percent — also have anemia.

Cancer occurs when cells mutate and multiply uncontrollably. It is a large group of diseases that affect different parts of the body and vary in severity. Among the most common types of cancer are lung, breast, and colorectal.

Anemia refers to a blood disorder that causes a low red blood cell count, making it hard for your blood to carry enough oxygen to support bodily functions. Anemia has been found to be both a risk factor for developing cancer and a side effect of cancer or its treatments.

Read on to learn more about the anemia-cancer connection.

While there are several types of anemia, iron deficiency anemia is the type that is most often linked to cancer. Iron deficiency anemia is caused by a lack of healthy red blood cells in the body.

There are several cancers that can attack blood cells, causing anemia. Chemotherapy cancer treatment can also cause anemia by slowing down the production of new blood cells.

Ultimately, researchers consider the link between cancer and anemia “multifactorial,” meaning that there’s more than just one reason someone with cancer may develop anemia.

Iron deficiency anemia is caused by a lack of a sufficient amount of the mineral iron to make healthy red blood cells. Your body makes red blood cells in bone marrow, a spongy material inside your body’s largest bones.

Red blood cells carry oxygen from the lungs to the rest of your body. A low red blood cell count or anemia occurs when:

  • the body does not make enough
  • red blood cells are lost through bleeding
  • the body starts to destroy its own red blood cells

When red blood cells are damaged or not numerous enough, they cannot carry oxygen efficiently throughout your body. This leads to symptoms including weakness and fatigue. Anemia can cause serious health complications if left untreated.

Iron deficiency anemia is most commonly caused by:

People most at risk for anemia include older adults, people who menstruate, people with alcohol use disorder, and those who experience neglect, or those who are unable to access enough nutrients.

While several types of cancer are linked to anemia, this is often due to different causes. We’ll overview some of the common cancer types associated with developing anemia and how this occurs.

Anemia and blood cancer

Blood cancer is one type of cancer commonly linked to anemia. That’s because blood cancer affects how your body produces and uses red blood cells.

Most of the time, blood cancers start in the bone marrow, causing abnormal blood cell growth. These abnormal blood cells push out healthy bone marrow cells, interfering with the production of red blood cells. This reduces your body’s ability to function normally and can cause bleeding or infection.

Anemia and bone cancer

Bone cancer is rare in adults. It begins when abnormal cells begin to grow in the bones into masses, or tumors, called sarcoma.

Experts don’t know exactly what causes most cases of bone cancer. However, some bone cancers appear to be linked to genetics, while others are related to previous exposure to radiation, such as radiation therapy for other, previous cancers.

Anemia and cervical cancer

Cervical cancer is caused by abnormal cell growth in the cervix, the lower part of the uterus that connects to the vagina.

The sexually transmitted infection human papillomavirus (HPV) is thought to cause most cases of cervical cancer. Abnormal growth of cells in the cervix often causes bleeding and iron deficiency, which can lead to anemia.

Anemia and colon cancer

Colon cancer is caused by abnormal growth of cells in the large intestine (the colon, also called the bowel). These cells can form tumors on or inside blood vessels in the colon that carry red blood cells.

Decades of research, including this 2018 study, suggests that these tumors can lead to bleeding and a loss of healthy red blood cells, common causes of anemia.

Many people with colon cancer experience rectal bleeding and bloody stool, as well as weakness and fatigue linked to their anemia. Iron deficiency anemia may be the first sign of colon cancer in some patients.

Anemia and prostate cancer

Prostate cancer is the abnormal growth of cells in the prostate, a small gland that produces and transports semen. People with prostate cancer sometime experience bleeding from their prostate, which can appear as blood in their semen.

A 2018 study suggests that bones are the most common site for prostate cancer to spread in men, and this can affect production of red blood cells. The bleeding and blood cell abnormalities can cause anemia.

Anemia can be mild, moderate, or severe. Often, the longer anemia goes untreated, the worse your symptoms can become. In both anemia and types of cancer, many people experience few to no symptoms in the very early stages.

People with anemia may also experience pale nails, gums, and lips in addition to pale skin.

Left untreated, anemia can cause serious health problems. Contact your doctor if you’re experience one or more of these symptoms. Routine screening and blood tests can help identify if anemia or cancer may be involved.

Most cancers are separated into stages. Usually the higher the stage, the more noticeable symptoms are, and the more aggressive the cancer is.

Symptoms of cancer vary depending on type. Here’s a very basic rundown of some of the signs of cancers most commonly linked to anemia, according to the NCI. Not every person with these cancers will experience all of the signs. Often, symptoms appear in mid to later stages of cancer.

Blood cancer

  • chest pain
  • chills
  • coughing
  • fever
  • frequent infections
  • itchy skin or rashes
  • loss of appetite and nausea
  • night sweats
  • shortness of breath
  • swollen lymph nodes

Bone cancer

  • bone pain
  • fatigue
  • fever
  • swelling and tenderness near bones
  • weakened bones and bone fractures

Cervical cancer

Colon cancer

  • abdominal pain, gas, cramps, and general discomfort
  • change in bowel habits and stool consistency
  • blood in stool
  • rectal bleeding
  • trouble emptying bowel
  • fatigue
  • weight loss
  • vomiting

Prostate cancer

  • sudden need to urinate
  • increased need to urinate, especially at night
  • blood in urine or semen
  • pain while urinating
  • back, hip, or pelvis pain
  • difficulty starting urine flow or not emptying bladder completely
  • erectile dysfunction
Key point

Different cancers can cause anemia for different reasons.

These include:

  • a loss of healthy red blood cells
  • bleeding from tumors
  • damage to bone marrow

Since there are several different medical situations that could lead to anemia, the process of diagnosis varies. Let’s go over the factors that impact how a doctor may approach diagnosing and treating anemia in people without cancer, with cancer, and those being evaluated for cancer.

Anemia with no clear cause

If you have symptoms of anemia without a pre-existing cancer diagnosis, your doctor will order several blood tests to investigate. These include:

If you are iron deficient but not menstruating (which can cause this deficiency), you will likely need a colonoscopy and upper endoscopy to rule out colorectal or gastric cancer. If you are menstruating but don’t respond to iron replacement treatment, or if you’re experiencing any rectal bleeding, you will also need these procedures.

Anemia with existing cancer diagnosis

It’s important to rule out cancer when treating anemia. Identifying a tumor can help doctors understand why you’re anemic.

If you’re anemic but already have a cancer diagnosis, your doctor likely already knows what is causing your anemia due to the thorough tests (including imaging, biopsies, and lab work) involved in your cancer treatment. Treatment for anemia in this context will focus on treating the underlying disease. Blood transfusions can also help counteract the anemia caused by cancer and its therapies.

The importance of cancer screenings

Everyone should get age-appropriate cancer screenings, which can vary depending on your risk factors. Screenings are exams done on people with no symptoms. These tests can catch cancer in its early stages before it becomes severe and causes more widespread health issues.

Common CDC-recommended cancer screenings include:

For the best possible outcome, it’s important to treat anemia and cancer at the same time if you have both of these conditions.

Treating anemia

If you have iron deficiency anemia, treatment may involve:

  • eating a diet that includes more iron-rich foods
  • working with your healthcare team to identify and address any bleeding (other than menstruation) concerns that could be contributing to your anemia
  • taking iron supplements

Treating cancer

Cancer treatments vary depending on the type of cancer.

Some common cancer treatments include:

  • Chemotherapy. This treatment is the administration of anti-cancer drugs delivered through a vein to kill cancer cells.
  • Radiation therapy. This therapy involves using high-powered energy beams like X-rays to kill cancer cells. Radiation therapy is often used before surgery to shrink tumors.
  • Surgery. This procedure involves removing entire cancerous tumors so that they stop growing and affecting the body. Depending on where the tumor is located, this may or may not be possible.

Learn more about advances in cancer treatment.

Consequences of cancer treatment

If you have severe anemia, you may have to delay your cancer treatment or reduce your dose until your anemia is better managed. Anemia can cause weakness and also make some cancer treatments less effective.

Your doctor will evaluate your best course of treatment to minimize possible complications caused by cancer treatment while you have anemia.

Blood transfusions

Blood transfusions are done at a hospital or special transfusion center. They involve infusing someone else’s healthy blood into your body intravenously, or via an intravenous (IV) line in a vein.

There are several types of blood transfusions, but the one used for anemia is called a red blood cell transfusion. The goal of this transfusion is to get healthy red blood cells into your body since you aren’t producing enough of your own.

Blood transfusions for anemia are usually used only if someone hasn’t responded to other treatments, or if they have active bleeding, cancer, or another serious health condition. Some people with cancer may require another type of blood transfusion, such as a plasma or platelet transfusion, to treat other effects of cancer on blood cells.

A blood transfusion uses blood compatible with your blood type and can take several hours to complete. After the process is complete, you may feel sore, or be bruised, at the area of IV insertion.

Experts consider anemia in those with cancer to be multifactorial in origin. It can result from preexisting health conditions, nutrient deficiencies, symptoms of the cancer itself, or as a result of the cancer treatment.

Anemia may reduce a cancer patient’s overall ability to recover from their treatment and ultimately enter remission. A 2015 study found older adult cancer patients lost a significant amount of functionality (ability to do daily activities and tasks) when they had anemia, compared with those without it.

If you have a cancer diagnosis, talk with your doctor about your risk of developing anemia and what steps you can take to prevent it. Keep track of your symptoms and attend regular checkups to ensure your red blood cell count is within a healthy range.