The short answer
Cancer can cause many different signs and symptoms, but most of these symptoms are caused by something other than cancer. Knowing the common warning signs helps you notice changes early and decide when to see a doctor.
Cancer can cause many different signs and symptoms depending on where it is.
Most symptoms that could signal cancer are actually caused by something less serious.
Common warning signs include a lump, unexplained weight loss, fatigue, and unusual bleeding.
A symptom that is new, lasting, or unusual for you is the most important reason to get checked.
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The whole article, with every detail and caution.
The simple version
This page is for anyone who has noticed a change in their body and wonders if it could be cancer. Cancer can cause many different signs and symptoms. They depend on where the cancer is and how big it is. Most of these symptoms are caused by something other than cancer. But some can be warning signs, so it is worth getting new or lasting changes checked.
When to get help sooner
Most warning signs on this page are checked over weeks. A smaller set means today, or right now.
- Call 911 or go to an emergency department if… you have trouble breathing that comes on suddenly or makes it hard to talk, or you have chest pain. Do not drive yourself.
- Call 911 or go to the nearest emergency department if… you vomit blood or something that looks like coffee grounds, or your stool is black and tarry.
- Call 911 or go to the nearest emergency department if… you have substantial bleeding, or bleeding that will not stop after a few minutes.
- Call 911 or go to an emergency department if… you have a seizure, a sudden severe headache, sudden confusion, being hard to wake, or sudden weakness, numbness or slurred speech. Do not drive yourself.
- Call 911 or go to an emergency department if… a fever, shivering or feeling very cold comes with confusion, a fast heartbeat, shortness of breath, or clammy skin. These can be signs of sepsis, a life-threatening emergency (CDC).
- Call 911 or go to an emergency department if… new back pain comes with leg weakness, numbness, or loss of bladder or bowel control.
- Call your care team right away, day or night, if… you are getting cancer treatment and have a fever of 100.4°F (38°C) or higher, chills, a sore throat, mouth sores, burning when you urinate, or any other sign of infection. A normal temperature is not a reason to wait. If you cannot reach your team, go to the emergency department.
Everything else here can be booked. These cannot.
Common warning signs
Signs worth paying attention to include:
- A new lump or swelling anywhere on the body.
- Unexplained weight loss.
- Ongoing tiredness that rest does not fix.
- Unusual bleeding or bruising.
- A sore that does not heal.
- A change in bowel or bladder habits.
- A cough or hoarseness that will not go away.
- A change in a mole or patch of skin.
- Fever or night sweats with no clear cause.
- Trouble swallowing, or changes in the mouth.
- Headaches, vision changes or a drooping face.
The pattern to watch for
You do not need to memorize every symptom. The pattern that matters most is a change that:
- Is new.
- Lasts more than a couple of weeks.
- Keeps getting worse.
- Is unusual for you.
A new, lasting, or unusual change is the signal to get checked — not any single symptom.
For specific situations, see the deeper explainers on shortness of breath, bloating, jaundice, loss of appetite, breast pain, blood in urine, rectal bleeding, anemia, vaginal discharge, persistent indigestion, and loss of balance.
When in doubt, ask
Only a doctor can find the cause of a symptom. Getting new or lasting symptoms checked early gives you peace of mind if it is nothing. If it is something, it gives you the best chance to act early.
Common questions
What are common warning signs of cancer?
Common possible signs include a new lump, unexplained weight loss, ongoing fatigue, unusual bleeding, a sore that does not heal, a change in bowel or bladder habits, a nagging cough, or a change in a mole. Any of these can also be caused by other conditions.
Do these symptoms mean I have cancer?
Usually not. Most of these symptoms are caused by something other than cancer. But because they can be signs of cancer, new or lasting ones should be checked by a doctor.
Which symptoms matter most?
A symptom that is new, lasts more than a couple of weeks, keeps getting worse, or is unusual for you is the most important reason to see a doctor.
Why get symptoms checked early?
Finding cancer early, when it is small and has not spread, often makes it easier to treat. Getting new or lasting symptoms checked promptly gives you the best chance to act if something is wrong.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Talk with a trained specialist or navigator
Cancer Explained provides educational guidance, but does not replace trained specialists, social workers, or your medical team.
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Get urgent help
Fever of 100.4°F (38°C) or higher during chemo, severe pain, or trouble breathing: call your cancer care team right away, day or night. Call 911 for an emergency.
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Plain-language explanation of the published sources cited on this page. AI-assisted, source-checked, not clinician-reviewed.
Last updated: 2026-09-29Next planned review: 2027-07-07
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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