Is Anemia a Sign of Cancer?

This page is for anyone told they have anemia, or a low blood count, who wonders if it could mean cancer. It explains what anemia is, the usual causes, where cancer fits in, and when to get help fast.

Anemia means your blood is short of healthy red cells. It is a result, not an illness in itself. The real work is finding out why.

MedlinePlus says iron deficiency anemia is the most common type of anemia. That single fact reframes the worry for most people who land here after a blood test.

Two questions drive everything that follows. Is your body losing blood or iron? Or is it failing to make enough red cells?

Mild anemia often causes nothing at all. As it deepens, MedlinePlus and the National Cancer Institute (NCI) list:

• tiredness.
• headaches.
• trouble concentrating.
• pale skin.
• a fast heartbeat.
• feeling lightheaded or dizzy.
• shortness of breath with mild activity or even at rest.

Some signs mean you need help right away.

Call 911 or go to an emergency department if you have:

• chest pain or pressure, or severe breathlessness at rest.
• fainting, or nearly fainting.
• skin or lips turning pale, blue or grey.
• sudden confusion.

These are signs of a possible emergency. When in doubt, call 911 rather than wait.

Slow anemia and fast anemia are different problems. If blood is leaving your body now, the clock speeds up.

Get emergency care if you vomit blood or coffee-ground material, pass black tarry stools, or the toilet water turns red.

Call your care team the same day if you have rectal bleeding, blood in your urine, or periods far heavier than usual, alongside a low blood count.

Once any urgent problem is ruled out, the next question is why your count is low. Most anemia has an ordinary explanation:

• iron loss from heavy periods or bleeding in the gut.
• a diet low in iron, vitamin B12 or folic acid.
• kidney disease and other long-term illnesses.
• inherited conditions such as sickle cell disease.
• problems absorbing iron, such as celiac disease or gastric bypass surgery.

MedlinePlus lists cancer among the possible causes of anemia. NCI says cancers that affect the bone marrow can cause anemia. It also says treatments such as chemotherapy and radiation therapy can cause it.

Cancer in the stomach or bowel can also cause blood loss, which is one reason clinicians look for the source of bleeding.

None of that makes cancer likely for any one person with a low count. It explains why your clinician wants a reason rather than just an iron tablet.

This is the part that surprises people. For iron deficiency anemia, MedlinePlus lists several ways to look for the source of blood loss. MedlinePlus says these may include colonoscopy, upper endoscopy and fecal occult blood testing, which checks stool for hidden blood.

The logic is simple. Iron can be lost through bleeding in the gut. A camera test looks where blood tests cannot.

Being offered endoscopy does not by itself mean your team suspects cancer. It means they want to find where the blood loss is coming from.

MedlinePlus says providers use blood tests such as a complete blood count and iron levels. They may then order tests to look for a bleeding source. Your team will choose the steps for you. Ask which step you are on and what the result would change.

Note your energy over the past few months, any bleeding you have seen, your period pattern, and your diet. List every medicine, including over-the-counter painkillers.

Bring old blood results if you have them. A count that has drifted down over two years tells a different story from one that dropped in a month. Lab Tests for Cancer explains what the numbers mean.

• MedlinePlus — Anemia
• MedlinePlus — Iron deficiency anemia
• National Cancer Institute — Anemia
• National Cancer Institute — Symptoms of Cancer