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Colorectal cancer (colon or rectal cancer) (needs checking)

Also called: Colorectal cancer, colon cancer, rectal cancer, bowel cancer

Cancer of the colon or rectum, usually starting as a polyp. Screening from age 45 finds polyps before they become cancer.

ScreeningFrom age 45
TestsColonoscopy or stool tests
Rising inAdults under 50

Overview

Most colon cancers grow slowly from polyps over 10 or more years.

Blood in stool, a change in bowel habits, or low iron needs checking at any age.

Symptoms

Common signs:

  • Blood in stool or a change in bowel habits
  • Colon polyps, a rectal lump, or blood mixed into the stool
  • Change in bowel habits lasting weeks, or thin stools

Less common

  • Belly pain
  • Tiredness from low iron
  • Weight loss
  • Thin stools

Look up a symptom: Losing weight without trying · Stomach pain

When to get medical care

Call 911Heavy bleeding, trouble breathing, chest pain, or fainting: call 911.
Get care todayNew or quickly worsening symptoms.
See a doctor soonSymptoms lasting more than 2 to 3 weeks.

Causes

Changes in a cell's genes that make it grow out of control. Most happen by chance or with age; some come from smoking, infections, or inherited genes.

Does it spread or run in families?

  • Cancer isn't contagious. You can't catch it from someone.
  • It can run in families. Tell your doctor if a parent, brother, or sister has it.

Who is more likely to get it

  • Age over 45
  • Family history
  • Inflammatory bowel disease
  • Smoking, heavy alcohol, red and processed meat

Diagnosis

Tests look for the cause. Most people checked for these symptoms don't have cancer.

Questions you may be asked

  • How long you've had symptoms
  • Family history of cancer
  • Smoking and alcohol

The exam

A physical exam.

Tests

Tests, if needed:

  • Colonoscopy:
  • Blood count:
  • CT scan:

Treatment

Get the symptoms checked rather than waiting. If cancer is found, a cancer team makes a plan with you.

Self-care

  • Write down your symptoms and when they started
  • Bring someone with you to appointments
  • Ask for a copy of test results
  • Quit smoking: it helps at every stage

Surgery, chemotherapy, radiation, and targeted therapy.

Prevention

To lower your risk or find it early:

  • Start screening at 45
  • Stay active
  • Eat fiber, limit processed meat

Which doctor treats this

  • Start with your primary care provider (family doctor or internist).
  • They may send you to an oncologist (cancer doctor), often with a surgeon and a radiation doctor.

Living with it

  • Keep a simple diary of symptoms, triggers, and medicines to bring to visits.
  • Bring a list of your medicines and questions to each visit.
  • Ask for a survivorship care plan when treatment ends.
  • Gentle activity, like walking, can ease tiredness.
  • Long-term illness can affect mood. Tell your doctor if you feel down or anxious.

Support groups and helplines

Back to school, work, or sports

  • Most people can keep working or going to school.
  • Ask about changes that help, like extra breaks or a flexible schedule. Workers may be covered by the ADA. Students may get a 504 plan.

Pregnancy and breastfeeding

  • If you're pregnant or planning to be, tell your prenatal provider about this condition.
  • Some cancer treatments can harm a baby. Ask about saving eggs before treatment if you want children later.
  • Don't start or stop any medicine on your own. Some are safe in pregnancy and some need to be changed.
  • Ask before taking any pain reliever. The FDA advises avoiding ibuprofen and naproxen after 20 weeks unless your doctor says to.
  • Breastfeeding: Most medicines are fine, but ask. The NIH LactMed database lists what's known about each one.

For caregivers

  • Go to visits when you can and take notes.
  • Keep a list of medicines, allergies, and doctors in one place.
  • Learn the warning signs that need fast care.
  • Take breaks and ask for help. Caregivers need care too.

Outlook

Cancers found early are much easier to treat, and treatments keep improving.

Support is available: ask about social workers, nutrition help, and support groups.

Getting ready for your visit

Bring a list of your symptoms and medicines.

What to bring

  • A list of your medicines and supplements
  • Notes on when symptoms started and what makes them better or worse
  • Past test results

Questions to ask

  • What tests do I need?
  • If it's cancer, what stage is it and what are my options?
  • Are there clinical trials for me?

Research studies

Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.

Search ClinicalTrials.gov for studies on Colorectal cancer (colon or rectal cancer) (needs checking)

Sources

Last updated 2026-11-12.