7 Warning Signs of Colon Cancer and Why Early Screening Saves Lives

Most people who develop colon cancer do not realise it is happening. The early signs are often subtle and easy to dismiss. A change in bowel habits may be blamed on diet, fatigue may be attributed to a busy schedule, and occasional abdominal discomfort may not seem serious enough to investigate. As a result, many people delay seeking medical advice until symptoms become more persistent or difficult to ignore.

This delay matters. Colon cancer often develops slowly over many years, creating a valuable window for early detection and treatment. When warning signs are overlooked or screening is delayed, the disease has more time to grow and spread, making treatment more complex.

In India, colon cancer is the fourth most commonly diagnosed cancer among both men and women, with 64,863 new cases and 38,367 deaths reported in 2022. While the number of cases is lower than in many Western countries, survival outcomes remain a concern. One of the biggest reasons is late diagnosis, with many patients reaching a specialist only after the disease has progressed to an advanced stage.

The good news is that colon cancer is one of the most preventable and treatable cancers when detected early. Recognising the warning signs and undergoing timely screening can lead to earlier diagnosis, more treatment options, and significantly better outcomes.

In this article, we’ll explain seven warning signs of colon cancer that should not be ignored and explain why early screening can save lives.

Key Takeaways

• Disease Burden: Colon cancer is the fourth most common cancer in India, with many cases detected at an advanced stage due to delayed diagnosis.
• Warning Signs: Persistent blood in the stool, a change in bowel habits, unexplained weight loss, or other ongoing symptoms should never be ignored.
• Early Detection Matters: Colon cancer is highly treatable when detected early, with significantly better outcomes than advanced-stage disease.
• Best Screening Tool: Colonoscopy remains the most effective method for screening, early detection, and removal of precancerous polyps.
• Who Should Get Screened: Adults over 45 years of age, as well as those with a family history or other risk factors, should discuss screening with a specialist even if they have no symptoms.

What is Colon Cancer?

The colon, also known as the large intestine, is the final part of the digestive system. Its main role is to absorb water from digested food and form stool before it passes into the rectum.

Colon cancer develops when cells in the lining of the colon begin to grow abnormally. In many cases, the disease starts as a small growth called a polyp. Over time, some polyps can become cancerous and grow into the deeper layers of the colon wall. If left untreated, the cancer may spread to nearby lymph nodes and other parts of the body. When cancers of the colon and rectum are discussed together, they are referred to as colorectal cancer.

One of the challenges with colon cancer is that it often develops slowly and may not cause noticeable symptoms in its early stages. This is why recognising warning signs and undergoing recommended screening are so important for early detection.

7 Warning Signs of Colon Cancer

Experiencing one of the symptoms mentioned below does not necessarily mean you have colon cancer. Many of these symptoms can also be caused by common conditions such as haemorrhoids, infections, irritable bowel syndrome, or dietary changes. What matters is persistent symptoms. If a symptom continues, keeps returning, worsens over time, or has no obvious explanation, it should be evaluated by a doctor. 

7 warning signs of colon cancer include:

1. Blood in or on the Stool

Blood in the stool is one of the most important warning signs of colon cancer and should never be ignored. It may appear as bright red blood on toilet paper or in the toilet bowl, or as dark, black, tarry stools when bleeding occurs higher up in the digestive tract.

Although haemorrhoids are a common cause of rectal bleeding, any unexplained blood in or around the stool should be medically evaluated. It is not possible to determine the cause based on appearance alone.

2. A Persistent Change in Bowel Habits

A lasting change in bowel habits, such as diarrhoea, constipation, or alternating between the two, may be a sign of colon cancer, particularly if it persists for more than a few weeks.

Some people also notice that their stools become consistently narrower than usual. Any unexplained change in bowel patterns that does not improve should be discussed with a doctor.

3. Persistent Abdominal Pain or Cramping

Ongoing abdominal discomfort, cramping, bloating, or pain that keeps recurring should not be ignored, especially when there is no clear cause.

As a tumour grows, it can affect the normal movement of stool through the colon and lead to discomfort, pressure, or pain.

4. A Feeling That the Bowel Does Not Empty Completely

Some people with colon cancer experience a persistent sensation that they still need to pass stool even after using the toilet.

This symptom, known as tenesmus, can occur when a tumour irritates the bowel or partially blocks the passage of stool.

5. Persistent Bloating or Excessive Gas

Frequent bloating or excessive gas that is not linked to specific foods and does not improve with dietary changes may sometimes be associated with colon cancer.

While these symptoms are common and often harmless, persistent bloating accompanied by other warning signs should be evaluated.

6. Unexplained Fatigue or Weakness

Feeling unusually tired for weeks or months without a clear reason can be a symptom of colon cancer.

Slow, ongoing blood loss from a tumour can lead to iron deficiency anaemia, causing fatigue, weakness, shortness of breath, and reduced energy levels. In some cases, unexplained anaemia may be the first clue that something is wrong.

7. Unexplained Weight Loss

Losing weight without intentionally changing your diet or exercise routine should always be taken seriously.

Unexplained weight loss can occur when cancer affects the body’s metabolism, appetite, or ability to absorb nutrients. When it occurs alongside other symptoms on this list, prompt medical evaluation is important.

Colon Cancer in Younger Adults 

Colon cancer is often considered a disease of older adults, but this is changing. Studies from India and around the world have reported a growing number of cases among adults under 50, including people in their 30s and 40s.

The exact reasons for this increase are still being studied. Researchers believe factors such as changing dietary patterns, obesity, physical inactivity, metabolic disorders, and alterations in the gut microbiome may play a role. However, no single cause has been identified, and many younger patients diagnosed with colon cancer do not have obvious risk factors.

One of the biggest concerns is that symptoms such as rectal bleeding, abdominal discomfort, or changes in bowel habits are often attributed to less serious conditions in younger adults. This can delay diagnosis and treatment.

If you are under 50 and experience any of these symptoms persistently, do not assume that your age protects you from colon cancer. Seeking medical advice early can help identify the cause and ensure timely treatment if needed.

What Causes Colon Cancer?

Colon cancer does not have a single cause. It usually develops as a result of several factors working together over time, including age, family history, medical conditions, and lifestyle habits. While having one or more risk factors does not mean you will develop colon cancer, it can increase your likelihood of developing the disease.

Age

The risk of colon cancer increases with age, particularly after 45 years. Although most cases are diagnosed in older adults, doctors are also seeing a growing number of cases in younger people, making awareness important for all age groups.

Family History and Inherited Conditions

Your risk is higher if a parent, sibling, or child has been diagnosed with colon cancer. Certain inherited conditions, such as Lynch syndrome and Familial Adenomatous Polyposis (FAP), can significantly increase the risk and may require earlier and more frequent screening.

Colon Polyps

Most colon cancers develop from polyps, which are abnormal growths that form in the lining of the colon. While many polyps are harmless, some can gradually turn into cancer over time. Detecting and removing polyps during a colonoscopy can help prevent colon cancer from developing.

Inflammatory Bowel Disease

People with long-standing inflammatory bowel diseases, such as ulcerative colitis and Crohn’s disease affecting the colon, have a higher risk of developing colon cancer. Regular monitoring is often recommended for these individuals.

Obesity and Physical Inactivity

Being overweight, particularly around the abdomen, and leading a sedentary lifestyle can increase the risk of colon cancer. Regular physical activity has been shown to support overall colon health and reduce cancer risk.

Diet

A diet high in red and processed meats, fried foods, and refined carbohydrates, and low in fibre, fruits, vegetables, and whole grains, may increase the risk of colon cancer. Adopting a balanced, fibre-rich diet can help support long-term digestive health.

Tobacco and Alcohol Use

Smoking and regular alcohol consumption are established risk factors for colon cancer. The risk may be even higher when both habits are present together.

Type 2 Diabetes

People with Type 2 diabetes have a higher risk of developing colon cancer. This may be linked to underlying metabolic and inflammatory changes that affect the body over time.

What are the Stages of Colon Cancer?

The stage of colon cancer describes how far the disease has spread at the time of diagnosis. Staging helps doctors determine the most appropriate treatment plan and provides important information about prognosis.

In general, the earlier colon cancer is detected, the more treatment options are available and the better the chances of successful treatment.

Survival rates and treatment outcomes generally improve when colon cancer is diagnosed at an earlier stage. This is why recognising symptoms promptly and undergoing recommended screening are so important.

Many cases of colon cancer can be detected before symptoms appear, and some precancerous polyps can even be removed during screening, helping prevent cancer from developing in the first place.

How is Colon Cancer Diagnosed and Screened?

Detecting colon cancer early often begins with recognising symptoms, but screening can identify cancer and precancerous polyps even before symptoms develop. If colon cancer is suspected, a combination of endoscopic procedures, imaging studies, and laboratory tests may be used to confirm the diagnosis, determine the stage of the disease, and guide treatment planning.

Colonoscopy

Colonoscopy is the most effective test for detecting colon cancer and identifying precancerous polyps. During the procedure, a thin, flexible tube with a camera is used to examine the inside of the colon.

If any suspicious areas are found, tissue samples (biopsies) can be collected for testing. Polyps can also be removed during the same procedure, helping prevent them from developing into cancer.

At RGCIRC, colonoscopy is performed using advanced high-definition endoscopy systems, including Narrow Band Imaging (NBI), which can help detect subtle or flat lesions that may be difficult to identify with conventional imaging.

Other Screening Tests

For individuals who are unable or unwilling to undergo a colonoscopy, other screening options may be considered. These include:

• Faecal Occult Blood Test (FOBT)
• Faecal Immunochemical Test (FIT)
• CT Colonography (Virtual Colonoscopy)

While these tests can help identify individuals who may require further evaluation, they do not replace the diagnostic and preventive benefits of a colonoscopy.

Imaging Tests for Staging

If colon cancer is confirmed on biopsy, additional imaging tests are performed to determine the stage of the disease and whether it has spread beyond the colon.

These may include contrast-enhanced CT scans of the chest, abdomen, and pelvis, as well as Digital PET-CT scans in selected cases. The information obtained helps doctors plan the most appropriate treatment strategy.

Molecular Testing for Personalised Treatment

For patients with advanced colon cancer, molecular testing can provide valuable information about the tumour’s genetic and biological characteristics.

At RGCIRC, advanced molecular profiling may include testing for RAS and RAF mutations, microsatellite instability (MSI), PD-L1 expression, and next-generation sequencing (NGS). These tests help identify patients who may benefit from targeted therapies or immunotherapy, allowing treatment to be tailored to the individual patient.

How is Colon Cancer Treated?

Colon cancer treatment is tailored to each patient and depends on several factors, including the stage of the disease, the location of the tumour, its molecular characteristics, and the patient’s overall health. At RGCIRC, every colon cancer case is reviewed by a dedicated GI and HPB Multidisciplinary Tumour Board to ensure that treatment decisions are personalised and evidence-based.

Polypectomy and Endoscopic Resection

When colon cancer is detected at a very early stage and remains confined to a polyp or the innermost lining of the colon, it may be possible to remove it completely during a colonoscopy. In selected cases, no additional surgery may be required.

Colectomy

Surgery is the primary treatment for most localised colon cancers. A colectomy involves removing the affected section of the colon along with nearby lymph nodes to reduce the risk of cancer spread.

At RGCIRC, colectomy can be performed using open, laparoscopic, or robotic techniques. Minimally invasive approaches, particularly robotic colorectal surgery, may offer benefits such as smaller incisions, less pain, and faster recovery in suitable patients.

Multivisceral Resection

In some cases, colon cancer may grow into nearby organs or structures. When this occurs, surgeons may need to remove the tumour along with the affected surrounding tissues or organs during the same operation to achieve the best possible outcome.

Chemotherapy, Targeted Therapy, and Immunotherapy

Some patients may require systemic treatment in addition to surgery. Depending on the stage and molecular profile of the cancer, treatment may be given before surgery to shrink the tumour, after surgery to reduce the risk of recurrence, or as the primary treatment for advanced disease.

Modern treatment options may include chemotherapy, targeted therapy, and immunotherapy, with the choice guided by detailed molecular testing and individual patient factors.

When Should You Consult a Doctor?

Do not wait for symptoms to become severe before seeking medical advice. Many of the warning signs of colon cancer appear early, when the disease is often more treatable. If a symptom persists, keeps returning, or has no obvious explanation, it is important to get it evaluated.

You should consult a specialist if you experience:

• Blood in or on the stool
• A change in bowel habits lasting more than two weeks
• Persistent abdominal pain, cramping, or bloating
• Unexplained weight loss
• Ongoing fatigue or weakness without a clear cause

Even if you do not have symptoms, you should discuss colon cancer screening with a specialist if you:

• Are 45 years of age or older
• Have a family history of colon cancer or colorectal polyps
• Have inflammatory bowel disease, such as ulcerative colitis or Crohn’s disease
• Have an inherited condition such as Lynch syndrome or Familial Adenomatous Polyposis (FAP)
• Have previously had colorectal polyps removed

Early evaluation and timely screening can help detect colon cancer at a stage when treatment is more effective and outcomes are generally better.

Why Choose RGCIRC for Colon Cancer Care?

Choosing where to receive colon cancer treatment can have a significant impact on diagnosis, treatment planning, and long-term outcomes. At RGCIRC, patients benefit from specialised expertise, advanced technology, and a multidisciplinary approach that ensures every treatment decision is tailored to the individual patient. Here’s why patients choose RGCIRC for colon cancer care:

Dedicated GI Oncosurgery Expertise

Colon cancer at RGCIRC is managed by a dedicated team of GI Oncosurgeons who specialise exclusively in cancer surgery. The department is recognised for its expertise in minimally invasive colorectal procedures, including laparoscopic and robotic surgery.

Treatment options span the full spectrum of disease, from endoscopic removal of early-stage cancers and polyps to complex procedures for advanced disease, including liver resection and HIPEC for selected patients with peritoneal metastases.

Multidisciplinary Tumour Board

Every colon cancer case is reviewed by the GI and HPB Multidisciplinary Tumour Board before treatment begins. The board brings together surgical oncologists, medical oncologists, radiation oncologists, gastroenterologists, radiologists, GI pathologists, and specialised support professionals to evaluate each case from multiple perspectives.

This collaborative approach helps ensure that treatment recommendations are evidence-based, personalised, and aligned with the patient’s specific clinical needs.

Molecular Testing and Precision Oncology

Advanced molecular testing plays an important role in modern colon cancer treatment. RGCIRC was among the early centres in India to establish a dedicated molecular oncology laboratory, enabling comprehensive tumour profiling for patients with advanced disease.

Testing may include:

• RAS and RAF mutation analysis
• Microsatellite instability (MSI) and mismatch repair (MMR) testing
• PD-L1 expression assessment
• Next-generation sequencing (NGS) for detailed molecular profiling

These insights help identify patients who may benefit from targeted therapies or immunotherapy and support more personalised treatment planning.

Accreditation and National Recognition

RGCIRC holds NABH and NABL accreditations, along with Green OT and Nursing Excellence certifications. These recognitions reflect the institute’s commitment to patient safety, quality care, and clinical excellence. RGCIRC has also been recognised among the World’s Best Specialised Hospitals by Newsweek and received leading national healthcare rankings.

Commitment to Accessible Cancer Care

As a not-for-profit cancer centre, RGCIRC is committed to making specialised cancer care accessible to a wider patient population. Through its Philanthropy Department, eligible patients may receive financial assistance and treatment support, helping reduce barriers to timely cancer care.

This commitment reflects the institute’s belief that access to quality cancer treatment should be guided by clinical need and not limited by financial circumstances.

Final Words

Colon cancer often develops slowly, and in many cases, the earliest warning signs are easy to overlook. However, recognising these symptoms and seeking timely medical advice can make a significant difference. Early detection not only increases the likelihood of successful treatment but can also help prevent cancer through the identification and removal of precancerous polyps.

If you have noticed persistent symptoms such as blood in the stool, changes in bowel habits, unexplained weight loss, abdominal discomfort, or ongoing fatigue, do not ignore them. Similarly, if you are over 45 years of age or have risk factors such as a family history of colon cancer, discussing screening with a specialist is an important step towards protecting your health.

To book a consultation or screening colonoscopy at RGCIRC | Call +91-11-4702 2222 (Rohini) / +91-11-4582 2222 (Niti Bagh, South Delhi) Book online or Download the RGCI Care app on iOS and Android 

OPD Hours: Monday to Saturday, 9:00 AM to 5:00 PM | Emergency Services: 24×7

Frequently Asked Questions (FAQs)

Can young adults get colon cancer?

Yes. Although colon cancer is more common in older adults, cases among people under 50 are increasing worldwide, including in India. Persistent symptoms such as rectal bleeding, changes in bowel habits, abdominal pain, or unexplained weight loss should never be ignored, regardless of age.

What are the common screening tests for colon cancer?

Colonoscopy is considered the gold standard for colon cancer screening because it allows doctors to examine the entire colon and remove polyps during the same procedure. Other screening options include the Faecal Immunochemical Test (FIT), Faecal Occult Blood Test (FOBT), and CT colonography.

At what age should colon cancer screening begin?

For adults at average risk, colon cancer screening is generally recommended from the age of 45. People with a family history of colon cancer, inflammatory bowel disease, or inherited genetic conditions may need to start screening earlier.

How often should I get a colonoscopy?

For most average-risk adults with a normal colonoscopy result, screening is typically repeated every 10 years. Individuals with polyps, a family history of colon cancer, or other risk factors may require more frequent surveillance based on their doctor’s recommendation.

Is colon cancer hereditary?

Some cases of colon cancer are linked to inherited genetic conditions such as Lynch syndrome and Familial Adenomatous Polyposis (FAP). In addition, having a close family member with colon cancer can increase your risk and may warrant earlier screening.

Can lifestyle changes reduce the risk of colon cancer?

Yes. Maintaining a healthy weight, staying physically active, eating a fibre-rich diet, limiting processed and red meat, avoiding tobacco, and reducing alcohol intake can help lower the risk of colon cancer.

Can colon cancer return after treatment?

Yes. Colon cancer can recur after treatment, which is why regular follow-up is important. Ongoing monitoring may include clinical examinations, blood tests, imaging studies, and surveillance colonoscopies to detect recurrence as early as possible.

How does colon cancer affect bowel habits?

Colon cancer can cause changes such as persistent constipation, diarrhoea, alternating bowel habits, thinner stools, a feeling of incomplete bowel emptying, or blood in the stool. Any unexplained change that lasts more than a few weeks should be evaluated by a doctor.

Where can I get screened for colon cancer near me?

If you are over 45 years of age, have a family history of colon cancer, or are experiencing symptoms such as blood in the stool or persistent changes in bowel habits, you should discuss screening with a specialist. RGCIRC offers comprehensive colon cancer screening services, including colonoscopy, advanced endoscopy, and diagnostic evaluation at its Rohini and Niti Bagh centres in Delhi.

Which hospital is best for colon cancer treatment in Delhi?

When choosing a hospital for colon cancer treatment, it is important to look for specialised GI oncology expertise, multidisciplinary care, advanced diagnostics, and access to the full range of treatment options. RGCIRC provides comprehensive colon cancer care, including screening, diagnosis, surgery, chemotherapy, targeted therapy, immunotherapy, and long-term follow-up under one roof.