Medical Oncologist
Emergency signs
Heavy Bleeding, Blood in Vomit — or Black Stools
Blood in your vomit or black, tarry stools during cancer treatment is not ordinary stomach trouble. It usually means active bleeding inside the gut, and bleeding on cancer treatment can escalate faster than it would otherwise. This needs emergency assessment today — not a wait-and-see approach.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed August 2026
- Go now, not tomorrow — Any blood in vomit or black tarry stools during cancer treatment is a reason to go to emergency today.
- Treatments affect clotting — Chemotherapy, targeted therapy and blood thinners all reduce your body's ability to stop bleeding on its own.
- Black stools are not always obvious — Black, tarry stools smell strongly and stick to the toilet bowl — this is blood from higher up in the gut, not a dietary effect.
- Tell the team everything you are taking — Blood thinners, aspirin and some herbal supplements all change how your team will manage you. Bring the full list.
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Blood in vomit or black, tarry stools during cancer treatment means active bleeding in the gut. NCCN and ESMO classify this as a medical emergency. Go to your nearest emergency department now — do not wait for a scheduled appointment or a callback.
If a symptom below applies to you, do not wait for a callback. Call 1800-202-8726 or go to your nearest emergency department.
Meet the Specialists
17+ senior cancer specialists. One panel for your case.
Trained at AIIMS, Tata Memorial, and leading international centres. Combined 150+ years of experience. Every complex case is reviewed by 3+ of them — together.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Surgical Oncologist
Surgical Oncologist
Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
Surgical Oncologist
Radiation Oncologist
Radiation Oncologist
Radiation Oncologist
Hematologist
Interventional Radiologist
Dr. Mohammed Imran
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
Surgical Oncologist
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Not sure whether this counts as an emergency?
Call the helpline. It is always better to check than to wait.
How do you tell a minor bleed from an emergency?
| Sign | Less urgent — still call your team today | Go to emergency now |
|---|---|---|
| Stool colour | Small streak of red on tissue after straining | Black, tarry, sticky stools or blood visible in the toilet bowl |
| Vomiting | No blood in vomit | Any blood present, or coffee-ground appearance |
| How you feel | Well, no dizziness or faintness | Dizzy, faint, short of breath, or racing heart |
| Bleeding from a wound or port | Oozing that stops with firm pressure | Bleeding that does not stop despite sustained firm pressure |
| Typically starts | Can appear at any point during treatment | Often soon after a dose change, a new blood thinner, or a low platelet result |
What to tell the emergency team when you arrive
Tell the triage nurse immediately that you are on cancer treatment. This changes how quickly they assess you and what tests they run first.
Bring your full medication list, or a photo of it on your phone. Blood thinners, aspirin, anti-inflammatory tablets and some herbal supplements all affect clotting, and the team needs to know about all of them.
If you know your most recent blood count result, mention it. A recent low platelet count tells the emergency team a great deal about why the bleeding started and how to manage it.
Do not eat or drink until the team has assessed you. Many causes of gut bleeding need a procedure, and an empty stomach is safer if that becomes necessary.
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- Protein in Urine (Proteinuria) During Treatment
- QT Prolongation: What It Means on Your ECG Report
- Raised Liver Enzymes (SGPT/SGOT) on Targeted Therapy
- Secondary Cancers After Long-Term PARP Inhibitor Use
- Severe Rash With Fever or Blistering: A Medical Emergency
- Skin Darkening, Depigmentation and Pigment Changes
- Slow Heart Rate and Dizziness on Certain TKIs
- Sun Sensitivity and Photosensitivity on Cancer Drugs
- Swallowing Difficulty and Reflux on Cancer Tablets
- Swelling of Face, Legs and Around the Eyes
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Common questions
Frequently asked questions
Is a small amount of blood in stool an emergency during cancer treatment?
A single small streak of red on tissue after straining is less likely to be immediately dangerous, but it still needs a call to your oncology team the same day. Any blood in the toilet bowl itself, black or tarry stool, or blood alongside dizziness or pain is an emergency. When you are on cancer treatment the threshold for acting is lower than usual, because treatments that affect your platelets or clotting can turn a small bleed into a significant one quickly.
Why are cancer patients at higher risk of serious bleeding?
Several things that are part of cancer treatment reduce your body's ability to form a clot and stop bleeding. Chemotherapy can lower your platelet count, and platelets are what seal a damaged blood vessel. Some targeted therapies affect blood vessel walls directly. Blood thinners, which many cancer patients take to reduce clot risk, slow clotting by design. And tumours can erode into nearby blood vessels. Any one of these makes a bleed harder to stop without medical help.
What does black tarry stool mean and how is it different from a dietary change?
Black, sticky, strongly smelling stool — called melaena — is blood that has been digested as it passed through the upper gut, from the stomach or upper small intestine. It does not look like fresh red blood, which is why it is sometimes mistaken for a change in diet or a supplement. Iron tablets can darken stools but do not produce a tarry, sticky texture with a strong smell. If you are unsure, treat it as a gut bleed and go to the emergency department — let the team confirm it is not.
Should I call my oncologist before going to the emergency department?
If any of the red-flag signs above apply to you, go to emergency first and call on the way, or ask someone with you to call. Do not delay leaving in order to reach your oncologist. Emergency departments are equipped to stabilise bleeding that cannot wait, and your oncology team can be contacted by the emergency team once you are there. If your symptoms are milder and you are genuinely unsure, call your oncology team or helpline first — they will tell you whether to go in immediately or be seen urgently at the clinic.