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ACS

Know the Symptoms of Colorectal Cancer

Detecting colorectal cancer early can improve your prognosis. Learn what to expect when going through the screening process, conversations to have with your doctor, and how to approach treatment.

Know the Symptoms of Colorectal Cancer

Spot the Warning Signs

Colorectal cancer is the third most common (non-skin) cancer in the United States. It is also a leading cause of cancer deaths in people under the age of 50. Screening can prevent colorectal cancer by finding and removing any polyps that could become cancerous. Colorectal cancer can be more easily and successfully treated when found early. However, it also is important to know that early warning signs can help catch cancer before it spreads.  

We want to help you to: 

  • Know when to start screening  
  • Notice early symptoms of colorectal cancer 
  • Talk clearly with your healthcare provider about symptoms 
  • Understand treatment options 

Early Onset Colorectal Cancer

Early onset colorectal cancer is colorectal cancer diagnosed before age 50. Early onset colorectal cancer is increasing. Symptoms in younger adults are sometimes missed, which can lead to delays in diagnosis.1 A recent study found that nearly half of young adults with colorectal cancer reported seeing blood in the toilet before diagnosis.2 The average time between noticing symptoms and diagnosis was more than 6 months.

If you notice concerning symptoms—especially rectal bleeding—do not “wait it out.” Ask to be evaluated.
colonoscopy.jpg

When Should Screening Start?

Most guidelines recommend starting colorectal cancer screening at age 45. Some people may need to start earlier, including those who have:

  • A family history of colorectal cancer
  • Advanced polyps
  • Inflammatory bowel disease (e.g., Crohn’s disease or ulcerative colitis)
  • A hereditary syndrome (e.g., Lynch syndrome)

Talk with your doctor about the best age for you to begin screening.

Screening Tests

Experts recommend colorectal cancer screening using either a direct visual test, such as colonoscopy, or a stool-based test. Colonoscopy offers the greatest potential to prevent colorectal cancer and to find it early. Other screening options are available but may not be as reliable as a colonoscopy. What’s most important to remember is that any screening is better than no screening.

Colonoscopy—The Gold Standard

A colonoscopy looks at the entire colon and rectum using a flexible camera. During a colonoscopy, doctors can remove polyps and take biopsies. For many average-risk adults, a colonoscopy is done every 10 years (or sooner if results are abnormal).

Stool-Based Tests 

These screening tests check stool for blood or abnormal DNA. They include:

  • Fecal Immunochemical Test (FIT)
  • Fecal occult blood test
  • Cologuard®

They are done every 1–3 years. A positive result usually means a follow-up colonoscopy is needed.

Other Screening Options
  • CT colonography (virtual colonoscopy)
  • Flexible sigmoidoscopy (looks at the lower colon)

These tests are usually done every 5 years (intervals vary by test and personal risk).

Additional Screening Resources

Early Symptoms to Look For

Pay attention to changes in your body. If you notice any of these symptoms, do not ignore them. Make an appointment with your doctor.

  • Blood in stool or toilet water—Blood in the stool is not always cancer, but it is never normal.  Any blood in your stool could mean that there is blood in your digestive tract. If the toilet water looks pink, red, or has clots, this may be a sign of bleeding in the digestive system.
  • Thin stool shape—Very thin or pencil-shaped stool, especially if this is new for you, can be a warning sign. This may happen if something is narrowing the colon, such as a growing tumor. If you notice ongoing changes in stool shape or bowel habits, see your doctor.
  • Ongoing belly pain, cramping, or bloating
  • Unexplained weight loss
  • Unusual tiredness or weakness—sometimes from low iron/anemia
  • A blood test shows anemia

Colon Cancer Symptom Checklist

It is important to talk with your doctor about your symptoms and family history. This helps guide next steps.

We created a printable symptom checklist to help you prepare for your appointment.

Colon Cancer Symptom Checklist

Verificador de síntomas de cáncer de colon

Conversation with Your Doctor

What Could It Be?

Make an appointment with your primary care doctor or a gastroenterologist. Your doctor will first look for common causes of symptoms that are not cancer and then decide if cancer testing is needed. 

Hemorrhoids and Other Anal Problems

Hemorrhoids are swollen veins in or around the anus. They are common and can cause:

  • Bright red bleeding
  • Pain or itching
  • A painful lump near the anus

Other conditions with similar symptoms include:

  • Anal fissure—a small tear that causes pain and bleeding
  • Anal abscess or fistula—an infection that causes pain or drainage
  • Rectal inflammation (proctitis)—irritation from infection or bowel disease

Important: These problems usually are not serious, but the symptoms can look like colorectal cancer. New or ongoing bleeding should always be checked by a clinician.

Inflammatory Bowel Disease (IBD)

IBD includes two long-term conditions:

  • Crohn’s disease, which can affect any part of the digestive tract
  • Ulcerative colitis, which affects only the colon and rectum

Common symptoms include:

  • Ongoing diarrhea
  • Belly pain or cramping
  • Blood in stool
  • Tiredness and weight loss
  • Anal pain, skin tags, drainage

IBD is not the same as irritable bowel syndrome (IBS). IBS does not cause inflammation or bleeding. People with IBD have a higher risk of colon cancer and need regular checkups.

Infectious Diarrhea

Some infections can cause diarrhea and bleeding. These infections come from germs in food, water, or close contact with others.

Common causes include:

  • Bacteria (Salmonella, E. coli, Shigella)
  • Viruses (Norovirus, Rotavirus)
  • Parasites: (Giardia)
Colorectal Cancer

Colorectal cancer starts in the colon or rectum. It often begins as small growths called polyps. Polyps are not cancer at first, but some can turn into cancer over time. 

Screening can find and remove polyps early, before they become cancer.

Early cancer may not cause symptoms. Later cancer symptoms may include:

  • Blood in stool
  • Changes in bowel habits
  • Belly pain
  • Tiredness
  • Weight loss

False Alarms Can Happen

Sometimes red-colored stool is caused by foods like beets or red food coloring. Still, bleeding should not be assumed to be from food without an exam and medical guidance.

What’s Next

What Might a Medical Provider Do?

After talking with you, your provider may recommend one or more of these steps:

  • A focused history and exam (including reviewing family history and risk factors)
  • A digital rectal exam—Your doctor may examine the rectum to check for blood, tumors, or other problems.
  • Direct visual exam—A colonoscopy is the best test for finding colorectal cancer. A flexible tube with a camera looks at the entire colon and rectum. Most people aged 45 and older need a colonoscopy every 10 years (or sooner if results are abnormal). Doctors can:
    • Remove polyps
    • Take biopsies
  • Blood tests—A doctor may have blood tests done to check for anemia or low iron.
  • Imaging tests—Imaging tests may be needed based on symptoms and exam.

If you have rectal bleeding, especially with a change in bowel habits, unexplained weight loss, or persistent abdominal pain, ask your provider whether a colonoscopy is needed—even if you are younger than 45 years old.

patient-comforting-.jpg

If You Test Positive for Colon Cancer

Hearing you have cancer is scary. Remember, treatment works well for many people, especially when cancer is found early.

Treatment depends on:

  • Cancer stage
  • Tumor location
  • Your overall health

Options may include surgery, chemotherapy, radiation therapy, or immunotherapy. Newer treatments are showing promise, especially for younger patients. Your care team will recommend a plan based on your specific cancer and goals.

Choosing the right treatment center is important—especially for rectal cancer and complex cases.

Find CoC and NAPRC hospitals near you using the ACS Find a Hospital search tool.

How to Find Quality Cancer Care

There are many places to get care after a colorectal cancer diagnosis. Patients should consult with their doctor and seek high-quality care. The following programs meet high standards and provide team-based cancer care:

  • American College of Surgeons Commission on Cancer (CoC)-accredited hospitals and facilities
  • American College of Surgeons National Accreditation Program for Rectal Cancer (NAPRC)-accredited hospitals and facilities
  • National Cancer Institute (NCI)-designated cancer centers
Resources

The following leading colorectal cancer organizations offer education and support for patients. They focus on prevention, support, research, and awareness:

ACS Commission on Cancer, ACS National Accreditation Program for Rectal Cancer (NAPRC), and the ACS Patient Education Committee produced this guide in collaboration with:

References
  1. Siegel RL, Wagle NS, Jemal A. Leading cancer deaths in people younger than 50 years. JAMA. Published online January 22, 2026. doi:10.1001/jama.2025.25467
  2. Demb J, Kolb JM, Dounel J, et al. Red flag signs and symptoms for patients with early-onset colorectal cancer: a systematic review and meta-analysis. JAMA Netw Open. 2024;7(5):e2413157. doi:10.1001/jamanetworkopen.2024.13157
  3. Kavalukas S, et al. Rectal bleeding in young adults linked to 8.5 times higher risk of colorectal cancer. American College of Surgeons. Published October 3, 2025. https://www.facs.org/media-center/press-releases/2025/rectal-bleeding-in-young-adults-linked-to-85-times-higher-risk-of-colorectal-cancer/
  4. U.S. Preventive Services Task Force. Colorectal cancer: Screening. U.S. Preventive Services Task Force. Published May 18, 2021. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/colorectal-cancer-screening 
Early Onset Colorectal Cancer Task Force

Marylise Boutros, MD, FACS, FASCRS, FRCSC 
Regional Digestive Disease Institute Vice Chair of Research; Staff Colorectal Surgeon; Medical Director LARS Center; Department of Colorectal Surgery, Cleveland Clinic Florida 
Clinical Professor of Surgery, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University

Dionne S. Christopher, PMP
Director, Prevention, Colorectal Cancer Alliance

Gregory D. Kennedy, MD, PhD
Chief Medical Officer, Cancer Service Line, UnityPoint Health

Najjia N. Mahmoud, MD, FASCRS 
Chief, Division of Colon and Rectal Surgery and Emilie and Roland T. deHellebranth Professor of Surgery, Penn Medicine 

Molly McDonnell
Director, Advocacy, Fight Colorectal Cancer 

Emmanouil P. Pappou, MD, PhD, FACS, FASCRS
Colorectal Surgery Service, Memorial Sloan Kettering Cancer Center

Jennifer Paruch, MD, MS, FASCRS
Director of Research for Colorectal Surgery, Ochsner Medical Center

Margot L. Savoy, MD, MPH, FAAFP
Chief Medical Officer, American Academy of Family Physicians

Diego Schaps, MD, MPH
General Surgery Residency Program, Duke University Medical Center

Robert Smith, PhD
Senior Vice President, Early Cancer Detection Science, American Cancer Society

Giovanna da Silva Southwick, MD, FACS, FASCRS
Colorectal Surgeon Staff, Director Clinical Research, Department of Colorectal Surgery, Ellen Leifer Shulman and Steven Shulman Digestive Disease Center

Steven D. Wexner, MD, FACS, FRCS(Eng), FRCS(Ed)
Physician Executive Director; System Chief, Colorectal Surgery; and Professor of Surgery, MedStar Georgetown University Hospital

Kathleen Maruyama, MSN, RN
Senior Manager, Patient Education, American College of Surgeons

Mandy Bruggeman
Senior Administrator, Patient Education, American College of Surgeons

This information is published to educate you about preparing for your surgical procedures. It is not intended to take the place of a discussion with a qualified surgeon who is familiar with your situation. It is important to remember that each individual is different, and the reasons and outcomes of any operation depend upon the patient’s individual condition.

The American College of Surgeons is a scientific and educational organization that is dedicated to the ethical and competent practice of surgery; it was founded to raise the standards of surgical practice and to improve the quality of care for the surgical patient. The ACS has endeavored to present information for prospective surgical patients based on current scientific information; there is no warranty on the timeliness, accuracy, or usefulness of this content.