ON THIS PAGE
Many people with colon and rectal cancers (known as colorectal cancer) don’t experience symptoms at all until the disease has reached a more advanced stage. When symptoms do occur, they affect the digestive system and can include bloody stool, abdominal pain, and changes in bowel patterns.
Though these symptoms can mimic other, more common conditions, it’s important not to ignore them and to see your doctor, especially if they persist.
Symptoms of Colon and Rectal Cancer
Colorectal cancer symptoms include:
- A change in bowel habits — such as persistent diarrhea, constipation, or stool narrowing — that lasts for more than a few days
- A feeling that you need to have a bowel movement that's not relieved by having one
- Rectal bleeding with bright red blood
- Blood in the stool, which may make it look dark
- Cramping or abdominal (belly) pain
- Weakness and fatigue
- Unintended weight loss
Although people with colorectal cancer may not have rectal bleeding or blood in the stool, these are, for many people, the most identifiable signs of the disease.
These symptoms occur when cancer bleeds into the digestive tract. This may occur very slowly over years, and as such, blood in the stool may not even be noticeable.
Over a period of time, this continuous blood loss can lead to a low red blood cell count, a condition called anemia.
Blood tests that diagnose anemia may be the first step in the process of getting a colon cancer diagnosis or a rectal cancer diagnosis.
Types of Colorectal Cancer
Colorectal cancer is cancer that starts in the colon or the rectum. There are several types of colorectal cancer, including:
- Adenocarcinomas The most common type of colorectal cancer, adenocarcinomas begin in the cells that line the surface of the colon.
- Carcinoid Tumors This type of cancer starts in the hormone-producing cells in the intestines.
- Gastrointestinal (GI) Stomal Tumors These tumors begin in the nerve cells of the wall of the GI tract. Sometimes these tumors are benign, but they can also be cancerous.
- Lymphomas While these cancers of the immune system typically occur in the lymph nodes, they can also start in other organs, such as the colon or rectum.
Symptoms of colon cancer may vary depending on which side of the organ it occurs:
- Left-sided colon cancer makes up the majority of colon cancer cases and causes digestive symptoms like changes in bowel habits and bloody stool.
- Right-sided colon cancer is less common and is more likely to cause symptoms like fatigue, weight loss, and anemia due to slow and ongoing bleeding.
Potential Complications of Colorectal Cancer
If colorectal cancer goes undiagnosed, it could lead to the following complications.
- Bowel Obstruction A tumor can partially or completely block the colon, which can lead to symptoms like pain, bloating, and nausea.
- Bowel Perforation This dangerous complication is a tear in the colon wall that can cause infection in the abdominal cavity and often requires emergency surgery.
- Bleeding Tumors can cause bleeding, potentially lead to anemia or, less commonly, a life-threatening hemorrhage.
- Metastasis The cancer can spread to distant organs like the liver, lungs, or lymph nodes, affecting their normal function.
There can also be complications in getting a colorectal cancer diagnosis. Even when symptoms develop, people with cancer and doctors may first think of common conditions, such as hemorrhoids or irritable bowel syndrome, which have similar symptoms.
What’s more, many younger people assume that colorectal cancer only affects the elderly, so they are liable to ignore symptoms. While the vast majority of colorectal cancer is still found in older people, rates in people younger than 50 are climbing sharply.
It’s estimated that by 2030, around 15 percent of all colorectal cancer cases will be diagnosed in younger adults.
In response to this trend, the American Cancer Society recommends that regular screening tests for people at average risk of colorectal cancer begin at age 45, rather than 50.
When to See a Doctor
If you notice any bleeding in your stool, see your doctor right away. Additionally, if you have ongoing digestive symptoms, don’t ignore them. Talk to a healthcare professional who can help you determine the cause.
Once you describe symptoms to your doctor, they will likely give you a medical exam.
The doctor will likely question you about your medical history and ask if you have any risk factors for colorectal cancer, including a family history of the disease, a history of colorectal cancer or precancerous polyps, inflammatory bowel disease such as Crohn’s disease or ulcerative colitis. Other risk factors may include obesity or excess weight, a low level of physical activity, heavy alcohol use, and smoking.
Once the doctor has your medical history, the next step might be a physical exam.
The doctor may also examine your rectum by placing a gloved and lubricated finger inside to feel for any abnormalities. They may order certain tests, including blood and fecal tests.
You may also leave the doctor’s office with a prescription for a diagnostic colonoscopy, during which a gastroenterologist examines the inside of the colon and rectum via a device inserted through the anus: a long, thin, and flexible lighted tube with a tiny video camera at the end.
If the exam reveals any suspicious growths, the gastroenterologist can remove tissue for a biopsy to determine whether or not there are any cancer cells.
Even if you don’t have symptoms, it’s important to get screened for colorectal cancer at the appropriate time. People who do not have risk factors for colon cancer should get screened regularly starting at age 45. This may be done through a variety of tests including, stool-based tests every one to three years, a colonoscopy every 10 years, or CT colonography or sigmoidology every five years.
People with a family or personal history of colorectal cancer, as well as those who are at an increased risk of the disease need to start screening earlier and should get tested more often. Your doctor will discuss testing options, as well as when you should start and how frequently you should get tested.
Resources We Trust
- Cleveland Clinic: Colon Cancer (Colorectal Cancer)
- American Cancer Society: What Is Colorectal Cancer?
- Mayo Clinic: Colon Cancer: Symptoms & Causes
- National Cancer Institute: Colorectal Cancer – Patient Version
- World Health Organization: Colorectal Cancer
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
- Colorectal Cancer Signs and Symptoms. American Cancer Society. January 29, 2024.
- Colon Cancer Symptoms. Johns Hopkins Medicine.
- What Is Colorectal Cancer? American Cancer Society. January 29, 2024.
- Colon Cancer Symptoms and Causes. Mayo Clinic. December 19, 2024.
- Stage 4 (Metastatic) Colon Cancer. Mayo Clinic. July 18, 2025.
- Sung H et al. Colorectal Cancer Trends in Younger Versus Older Adults: An Analysis of Population-Based Cancer Registry Date. The Lancet. January 2025.
- Matar S et al. The Role of the Pathologist in Renal Cell Carcinoma Management. Hematology/Oncology Clinics of North America. May 29, 2023.
- American Cancer Society Guideline for Colorectal Cancer Screening. American Cancer Society. January 29, 2024.
- Colon Cancer (Colorectal Cancer). Cleveland Clinic. October 28, 2025.
- Colon Cancer Diagnosis & Tests. Mayo Clinic. December 19, 2024.
Meet Our Experts
Yuying Luo, MD
Medical Reviewer
Yuying Luo, MD, is an assistant professor of medicine at Mount Sinai West and Morningside in New York City. She aims to deliver evidence-based, patient-centered, and holistic care ...
Pamela Kaufman
Author
Pamela Kaufman assigns and edits stories about infectious diseases and general health topics and strategizes on news coverage. She began her journalism career as a junior editor on...