Learn About Colorectal Cancer Symptoms and Signs

Understanding Colorectal Cancer: What It Is and Why Awareness Matters

Colorectal cancer is a disease in which malignant cells form in the colon or rectum. The colon is the large intestine, and the rectum is the final section of the digestive tract. Together, they make up a roughly six-foot-long organ that absorbs water and nutrients from food before the body eliminates waste. When abnormal cells grow out of control in this area, they can develop into cancer that spreads to other parts of the body if left untreated.

According to the American Cancer Society, colorectal cancer is the third most common cancer diagnosis in both men and women in the United States. In 2024, the organization estimates there will be approximately 106,970 new cases of colon cancer and 46,050 new cases of rectal cancer. The good news is that colorectal cancer is often preventable and highly treatable when caught in early stages, making awareness of symptoms and signs critically important.

Risk factors vary from person to person. Age is one significant factor—the risk increases substantially after age 45, which is why screening recommendations often begin at this age. Family history of colorectal cancer, inherited genetic conditions like Lynch syndrome, inflammatory bowel diseases such as Crohn's disease or ulcerative colitis, and lifestyle factors including diet, physical activity level, smoking, and alcohol use all play roles in determining individual risk.

Understanding the difference between symptoms and signs is important. Symptoms are changes a person notices and feels in their body, such as pain or bloating. Signs are physical evidence that healthcare providers can observe or detect during an examination or test. Both matter when it comes to colorectal cancer because early detection through awareness of either can lead to better outcomes.

Practical Takeaway: Familiarize yourself with your personal risk factors. If you have a family history of colorectal cancer, inflammatory bowel disease, or are over age 45, discuss screening options with a healthcare provider. Knowing your risk level helps you understand why certain symptoms warrant medical attention.

Common Early Symptoms: Changes in Bowel Habits and Bleeding

Changes in bowel habits represent one of the most commonly reported early symptoms of colorectal cancer. These changes may include constipation, diarrhea, or alternating patterns between the two that last longer than a few weeks. A person might notice that their stools become narrower than usual or have a different texture. Some individuals report a feeling that the bowel has not completely emptied even after a bowel movement, a sensation sometimes called tenesmus. These changes should not be ignored, particularly if they persist for more than two weeks without an obvious cause like dietary changes or illness.

Rectal bleeding is another warning sign that warrants medical evaluation. This may appear as bright red blood in the stool or on toilet paper after bowel movements. While hemorrhoids are a common, non-cancerous cause of bleeding, colorectal cancer can also present this way. The distinction matters because a healthcare provider must determine the actual source. Blood in the stool can also be darker and less visible—sometimes the stool appears tarry or very dark, which may indicate bleeding higher up in the colon. Any persistent rectal bleeding, regardless of how minor it seems, should be reported to a healthcare provider.

Abdominal pain or cramping that does not go away is another early symptom some people experience. This pain may be localized to one area or feel general across the abdomen. It may be constant or come and go. Bloating or a persistent feeling of fullness can also occur, even after eating small amounts. Some individuals describe a sense of gas or pressure that does not resolve with typical remedies. These symptoms sometimes lead people to assume they have a temporary digestive issue, but when they persist beyond a few weeks, medical evaluation becomes important.

Fatigue and weakness can accompany early colorectal cancer, sometimes before other obvious symptoms appear. This fatigue differs from normal tiredness—it persists despite adequate rest and may interfere with daily activities. The fatigue can result from chronic bleeding that leads to anemia, a condition in which the body lacks enough healthy red blood cells to carry oxygen effectively. A person with anemia may notice they feel short of breath with minimal exertion or that their usual activities leave them unusually exhausted.

Practical Takeaway: Keep a brief record of any digestive changes that last more than two weeks. Note when they started, whether they improved or worsened, and any associated symptoms like bleeding or pain. This information helps healthcare providers make an accurate assessment. Do not assume symptoms are minor or will resolve on their own without evaluation.

Understanding Less Obvious Symptoms and Advanced Warning Signs

Not all colorectal cancer symptoms are obvious. Some people experience unexplained weight loss—losing 10 pounds or more without intentional dieting or increased exercise. This weight loss occurs because cancer cells consume nutrients and energy from the body, and sometimes because the cancer causes a decreased appetite or difficulty eating. Additionally, a person might feel full quickly when eating or experience nausea. These subtle changes sometimes go unnoticed or are attributed to stress or aging, but they warrant investigation when they occur without clear explanation.

Anemia-related symptoms sometimes appear before other signs. Because chronic bleeding from a colorectal tumor can cause iron-deficiency anemia, a person might experience shortness of breath, dizziness, pale skin, or a rapid heartbeat. Blood tests that reveal low iron levels or low hemoglobin counts can sometimes be the first objective sign that prompts further investigation. Healthcare providers who see these lab abnormalities in patients with digestive symptoms often recommend colorectal screening.

As colorectal cancer advances, symptoms may become more pronounced. A person might develop a complete or partial blockage in the colon, which causes severe constipation, inability to pass gas, severe abdominal pain and swelling, or vomiting. These signs represent a medical emergency because a blocked colon prevents normal waste passage and can damage the bowel. Additionally, if cancer spreads beyond the colon and rectum to other organs, symptoms specific to those locations may appear. For example, cancer that spreads to the liver can cause pain in the upper right abdomen, swelling, or jaundice (yellowing of the skin and eyes).

Some people have colorectal cancer with no symptoms at all—the disease is discovered only during routine screening procedures. This is actually one reason screening is so important. People aged 45 and older are now recommended to begin colorectal cancer screening, even without symptoms. Those with higher risk factors may need screening to begin earlier. The absence of symptoms does not mean absence of disease, particularly in early stages when treatment is most effective.

Practical Takeaway: Unexplained weight loss, persistent fatigue, or anemia symptoms deserve investigation. These are less frequently discussed symptoms of colorectal cancer but can be early indicators. Mention these changes to your healthcare provider, particularly if multiple symptoms occur together or persist for several weeks.

Who Should Be Concerned: Risk Factors and Screening Recommendations

The American Cancer Society updated its colorectal cancer screening recommendations in 2021, lowering the starting age from 50 to 45 for people at average risk. This change reflects increasing rates of colorectal cancer in younger adults. Anyone aged 45 and older should discuss screening options with their healthcare provider. Those aged 50 and older fall into a standard-risk category that should definitely pursue screening, and many insurance plans cover screening for this age group without cost-sharing.

Certain risk factors warrant earlier or more frequent screening. People with a personal history of colorectal cancer or polyps should follow their healthcare provider's recommendations, which typically involve more frequent screening intervals. Those with a family history of colorectal cancer in a first-degree relative (parent, sibling, or child) should discuss screening with a provider, potentially starting before age 45. If the family member was diagnosed before age 45, screening may begin even earlier. People with hereditary conditions like familial adenomatous polyposis (FAP) or Lynch syndrome have very high colorectal cancer risk and require specialized monitoring starting in childhood or early adulthood.

People with inflammatory bowel disease, including Crohn's disease or ulcerative colitis, face increased colorectal cancer risk, particularly if they have had the disease for many years or if it affects a large portion of the colon. Lifestyle factors also influence risk. Smoking, heavy alcohol consumption, a diet high in red and processed meats, obesity, and physical inactivity all increase colorectal cancer risk. People with diabetes also face