Is Your Fatigue a Symptom of Cancer?

Could your fatigue be the first symptom of cancer? At one point or another, we have all experienced fatigue. For most of us, it is temporary, usually caused by stress or being overworked.

For some people, however, fatigue can become persistent, occurring daily. When fatigue becomes frequent, it is natural to be concerned about what may be causing it.

One of the first things many people think maybe the culprit for their fatigue is cancer. When might feeling tired be a sign of cancer and how often is it?

woman relaxing on sofa
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We often hear about cancer patients who are extremely fatigued, but a lot of cancer-related fatigue is caused by the side effects of cancer treatment, not always cancer itself. In other words, for people with many cancers,​ the fatigue begins after diagnosis.

While fatigue alone without other symptoms is uncommon in many cancers, for people with leukemias and lymphomas fatigue may well be the first symptom.

Defining Cancer Fatigue

It's important to define the type of fatigue that could be the first symptom of cancer. Cancer fatigue isn't ordinary tiredness. It's not usually the kind of sleepiness that you can push through by getting a good night of sleep, or with a cup of coffee.

People describe this type of fatigue as "whole-body tiredness." It's also something that often disrupts life. People become frustrated at their inability to participate in normal activities and find that their tiredness is impacting their jobs and relationships.

Causes of Cancer Fatigue

Someone with cancer may experience fatigue for several reasons.

With leukemia and lymphoma, cancer cells in the bone marrow can interfere with the normal production of blood cells. This can lead to anemia, and anemia can then lead to fatigue.

Colon cancer and stomach cancer can cause anemia through blood loss in the bowels, likewise leading to fatigue.

The metabolic processes of tumors can also contribute to fatigue. Cancer cells aggressively compete for nourishment with normal cells. 

Some cancers lead to fatigue by disrupting normal hormone functioning. Others secrete substances known as cytokines, which in turn can cause fatigue.

Fatigue has many causes besides cancer, though. In that respect, fatigue accompanied by unintentional weight loss is more concerning than fatigue alone.

Seeing a Doctor for Fatigue

When your chief complaint is fatigue, cancer isn't likely to be the first thing on your doctor's mind. Fatigue is related to many other conditions, and your doctor will want to rule out the most common causes first.

This will be accomplished through a physical and routine blood work. Your doctor will likely order a few different blood tests, especially tests to check on your thyroid function.

During your visit, your doctor may ask several questions relating to your quality of life and what factors may contribute to your fatigue. Possible questions include:

  • How many hours do you work? Are you stressed at work?
  • Have you had any major life changes, such as marriage, birth, or death?
  • How often do you exercise?
  • Do you sleep well? How much sleep do you get?
  • How is your diet?
  • Do you have a family history of thyroid disease?

It is important to remember that fatigue is not exclusive to cancer. If you are experiencing fatigue, it may be related to a less serious condition or have a lifestyle cause.

A Word From Verywell

If you're living with cancer, you already know how cancer fatigue is different from other types of fatigue. Even though it's common and even expected, talk to your doctor if you are experiencing fatigue.

There are several causes of fatigue with cancer that don't have an easy solution, but there are also many treatable causes of fatigue.

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Article Sources
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  1. American Cancer Society. What is Cancer-Related Fatigue? Last Medical Review October 22, 2018.

  2. Dunlop RJ, Campbell CW. Cytokines and Advanced CancerJournal of Pain and Symptom Management. 2000;20(3):214-232.

  3. National Institute of Diabetes and Digestive and Kidney Diseases. Hypothyroidism (Underactive Thyroid). Published August, 2016.

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