The short answer
Some cancer treatments, such as chemotherapy and targeted therapy, can lower the number of platelets—the cells that help blood clot. When platelets are low, you may bruise or bleed easily and see tiny purple or red spots on your skin. This is called thrombocytopenia. Tell your healthcare team about these changes, and call right away for serious bleeding.
Some treatments, such as chemotherapy and targeted therapy, can lower the number of platelets in the blood.
Platelets are the cells that help your blood clot and stop bleeding.
When platelets are low, you may bruise or bleed easily and have tiny purple or red spots on your skin.
A low platelet count is called thrombocytopenia.
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The full explanation.
Why bleeding and bruising can happen
Some cancer treatments, such as chemotherapy and targeted therapy, can increase your risk of bleeding and bruising. These treatments can lower the number of platelets in the blood. Platelets are the cells that help your blood clot and stop bleeding.
When your platelet count is low, you may bruise or bleed a lot or very easily and have tiny purple or red spots on your skin. This condition is called thrombocytopenia.
Tell your doctor or nurse if you notice any of these changes.
Ways to manage bleeding and bruising
If you are at increased risk of bleeding and bruising, these steps may help:
- Avoid certain medicines. Many over-the-counter medicines contain aspirin or ibuprofen, which can increase your risk of bleeding. When in doubt, check the label. Ask your healthcare team for a list of medicines and products to avoid. You may also be advised to limit or avoid alcohol if your platelet count is low.
- Take extra care to prevent bleeding. Brush your teeth gently with a very soft toothbrush. Wear shoes, even inside. Be extra careful with sharp objects, and use an electric shaver rather than a razor. Use lotion and lip balm to prevent dry, chapped skin and lips. Tell your doctor or nurse if you are constipated or notice bleeding from your rectum.
- Care for bleeding or bruising. If you start to bleed, press down firmly on the area with a clean cloth and keep pressing until the bleeding stops. If you bruise, put ice on the area.
Ask your team ahead of time how long you should wait for bleeding to stop before you call them or go to the emergency room. Knowing your own number is easier than deciding in the moment.
When to get help sooner
- Call 911 or go to an emergency department if you have a bad headache, changes in how well you see, confusion, or you feel very sleepy. These can be signs of bleeding in the head.
- Call 911 or go to an emergency department if bleeding is heavy and will not stop with firm pressure, or you are vomiting blood.
- Call your care team the same day if bleeding does not stop after a few minutes, you bleed from your mouth or nose, your urine is red or pink, or your stools are black or bloody.
- Call your care team the same day if you bleed from your vagina when you are not having your period, or your period is heavier or lasts longer than normal.
- Call your doctor immediately if you have a temperature of 100.4°F (38°C) or higher. Treatment that lowers platelets usually lowers infection-fighting white cells too. The CDC says a fever during chemotherapy is a medical emergency, so call right away rather than waiting for your next appointment (CDC).
- Call your care team within a day or two if you notice new bruises without an injury, or tiny purple or red spots on your skin.
Sources
Words to know
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Common questions
What is thrombocytopenia?
Thrombocytopenia is a condition in which the number of platelets in the blood is low. Platelets help your blood clot and stop bleeding. When your platelet count is low, you may bruise or bleed easily and have tiny purple or red spots on your skin.
Why do some cancer treatments cause bleeding and bruising?
Some cancer treatments, such as chemotherapy and targeted therapy, can lower the number of platelets in the blood. Because platelets help your blood clot, having fewer of them can lead to easier bleeding and bruising.
What bleeding problems should I call my doctor about?
Call for bleeding that doesn't stop after a few minutes; bleeding from your mouth or nose or when you vomit; vaginal bleeding outside your period; red or pink urine; black or bloody stools; or heavier or longer periods than normal. Also call for head or vision changes such as bad headaches, changes in how well you see, confusion, or feeling very sleepy.
Which medicines should I be careful about?
Many over-the-counter medicines contain aspirin or ibuprofen, which can increase the risk of bleeding, so check the label. Ask your healthcare team for a list of medicines and products to avoid. You may also be advised to limit or avoid alcohol if your platelet count is low.
What can I do at home to prevent bleeding?
Brush your teeth gently with a very soft toothbrush, wear shoes even inside, be careful with sharp objects, and use an electric shaver instead of a razor. Use lotion and lip balm to prevent dry, chapped skin. If you start to bleed, press firmly with a clean cloth until it stops; for a bruise, put ice on the area.
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Last updated: 2026-08-18Next planned review: 2027-01-02
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. We do not employ clinicians and do not intend to — our work 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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High-risk topic — talk to your care team. This topic can involve urgent, individual medical decisions. This page is general education only: it cannot tell you whether your situation is an emergency or what you personally should do. Follow your oncology team's instructions and contact them for individual guidance.
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.
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. We do not employ clinicians and do not intend to — our work 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 checked line by line against the sources listed on it. That confirms the sources support what the page says. 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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