Medical Oncologist
Urgent care
Blood in the motions during chemotherapy
It is never something to watch and wait on during chemotherapy. It often turns out to be minor, but that is a conclusion for your team after looking, not one to reach at home. Treatment lowers the cells that make blood clot, and the gut lining is more fragile, so bleeding that would have stopped on its own before may not stop now. This page covers what to note and when to go straight in.
NG
Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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The short answer
Is blood in the motions ever normal during chemotherapy?
No. It is never something to watch and wait on during chemotherapy. It may turn out to be something minor, and often it does, but that is a conclusion for your team to reach after looking, not one to reach at home. Report it the same day.
The reason is platelets. Chemotherapy lowers the cells that make blood clot, so bleeding that would have stopped on its own before treatment may not stop now. At the same time, the lining of the gut is more fragile and infection is more likely. Those three things together are why the threshold is set low.
What you are being asked to do
Not to panic, and not to ignore it. Look at what you are actually seeing, note it down, and call. If there is a fever, a lot of blood, black tarry motions, severe pain or dizziness with it, go straight to an emergency department rather than waiting for a call back.
If you can, take a photograph, or do not flush. It sounds unpleasant and it genuinely helps the doctor.
!
Go to the emergency department now, not in the morning
Black, sticky, tar-like motions · a large amount of fresh blood · a fever alongside the bleeding · severe stomach pain, or a swollen hard stomach · dizziness, fainting, a racing heart or breathlessness · vomiting blood or something that looks like coffee grounds · bleeding that will not stop. Go to the nearest emergency department and say clearly that the person is on chemotherapy. Do not take a painkiller from home first — several of them make bleeding worse.
Not sure whether this applies to you?
Ask an oncologistWhat it can be
The usual explanations, from minor to serious
All of these need reporting. The list is here so you know what your team is thinking about, not so you can decide between them.
Piles or a tear at the back passage
The commonest and least worrying cause. Usually bright red blood on the paper or on the surface of the motion, often with pain on passing it, and often after a stretch of constipation or loose motions.
Still report it because
- Low platelets make it bleed more
- A break in the skin is a route for infection
An irritated or inflamed gut lining
The drugs thin the gut lining the way they thin the mouth lining, and it can bleed. Usually comes with loose motions and cramping in the days after a cycle.
Low platelets
When the clotting cells fall far enough, bleeding can start without much provocation, and may show up in other places too — gums, nose or bruises. This is a blood test away from being answered.
Mention any nosebleeds, gum bleeding or new bruises when you call. They are part of the same picture.An infection in the gut
Blood with loose motions and a fever. This combination must not be treated at home with an anti-diarrhoeal, because slowing the gut keeps the infection in during the days when counts are lowest.
An ulcer or bleeding higher up
Bleeding from the stomach or upper gut turns the motion black and sticky rather than red. That is an emergency rather than a phone call, and it is made more likely by steroids and by some painkillers.
Something being treated, or something new
In bowel and some other cancers, bleeding can come from the disease itself. It can also come from something unrelated that would have needed investigating anyway. Either way it is assessed rather than assumed.
Before you call
What your team will ask, and what to have ready
The colour is the first question. Bright red usually means bleeding low down, near the back passage. Dark red or maroon mixed through the motion suggests higher up. Black and sticky suggests the stomach or upper gut and is the most urgent of the three.
The rest of the picture
How much — streaks on the paper, or the water coloured. How many times it has happened. Whether there is pain, and where. The temperature, taken properly with a thermometer. Whether there is bleeding anywhere else, such as gums or nose. When the last blood count was done and what it showed, if you have the report.
The medicine list matters here more than usual
Take everything, including blood thinners, painkillers bought over the counter, steroids and any traditional or ayurvedic preparations. Several ordinary painkillers both cause bleeding and make it harder to stop, and that is often the piece that explains the whole episode.
Do not start or stop a blood thinner on your own, even now. Tell the team you are on one and let them decide.Being straight with you
What this page cannot tell you
It cannot tell you where the bleeding is coming from. Colour is a guide, not a diagnosis, and the same appearance can have several causes. Working it out usually needs a blood count and sometimes a camera test or a scan.
It also cannot tell you whether it is serious. A small amount of bright red blood from a tear is usually minor in someone with normal counts, and the same amount can matter in someone whose platelets have dropped. The counts are the missing piece, and only a blood test supplies them.
What to do next
If any of the emergency signs are present, go in now. Otherwise call the helpline today rather than waiting for the next appointment, with the colour, the amount, the temperature and the medicine list ready. Keep fluids going in and avoid painkillers until you have been advised.
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Questions we are asked
Common questions about blood in the motions
It is only a streak on the paper. Do I really need to call?
Yes, the same day. It may well be a small tear or piles, and often it is. But during chemotherapy the platelets that stop bleeding may be low, and a break in the skin is a route for infection at the worst possible time. A phone call settles it quickly; waiting does not.
What do black motions mean?
Black, sticky, tar-like motions usually mean bleeding higher up in the stomach or upper gut, and that is an emergency rather than a phone call. One exception is iron tablets, which darken motions harmlessly. Do not rely on that explanation yourself — go in and tell them you take iron.
Could it be from the piles I have always had?
Quite possibly, and piles do flare during treatment because of constipation, loose motions and straining. It still needs reporting, because low platelets change how much they bleed and how long it takes to stop. Mention that you have a history of them when you call.
Should I stop my blood thinner?
Not on your own, and not without speaking to a doctor, even with bleeding. Stopping some blood thinners abruptly carries its own risk. Tell the team immediately that you are on one, and let them make the decision. Take the exact name and strength with you.
Will I need a blood transfusion?
Only if the counts or the amount of bleeding call for it, and that is decided from blood tests rather than appearances. Many people who report bleeding need no transfusion at all. If it is needed, it is a routine part of supportive care and is arranged quickly.
Can I take something to stop the bleeding at home?
No. Do not use leftover medicines, and in particular avoid painkillers from the drawer, because several of the common ones make bleeding more likely and harder to stop. Keep fluids going, note what you are seeing, and let the team decide what is needed.
Is it dangerous to have a camera test during chemotherapy?
It is done when needed, with the timing chosen around your blood counts. Your team will check platelets first and may wait for counts to recover or support them beforehand. If the bleeding is significant, the test happens sooner because finding the source matters more.
Will this delay my treatment?
It may, depending on what is found and what your counts are doing. A delay decided for this reason is a considered one, not a setback. Reporting early usually protects the schedule better than waiting, because a small problem dealt with quickly interrupts less than a large one dealt with late.
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Sources
- National Cancer Institute — Gastrointestinal Complications (PDQ)
- Cancer Research UK — Low platelets and bleeding problems
- Macmillan Cancer Support — Bleeding problems and cancer treatment
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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