Medical Oncologist
Bevacizumab side effects
Bleeding and Bowel Perforation — Risks on Bevacizumab
Bevacizumab works by blocking blood vessel growth, which is how it fights cancer — but that same mechanism raises your risk of bleeding, slows wound healing, and rarely causes a tear in the bowel wall. Most bleeding is minor and manageable. Knowing which signs need urgent action could protect you from the rare event that does not wait.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed August 2026
- Most bleeding is minor — Nosebleeds and small bruises are common. They are manageable at home with simple pressure.
- Gut symptoms are never minor — Blood in your stool or vomit, or sudden severe abdominal pain, needs emergency care.
- Bowel perforation is rare but fast — A tear in the bowel wall is a surgical emergency that usually announces itself with sudden, severe pain.
- Wound healing is slowed — Tell any surgeon or dentist you are on bevacizumab before any planned procedure.
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Bevacizumab raises the risk of bleeding, poor wound healing, and — rarely — bowel perforation. Minor nosebleeds are common and manageable at home. Any heavy bleeding, blood in your vomit or stool, or sudden severe abdominal pain needs same-day or emergency assessment — not a wait-and-watch approach.
Managing minor bleeding at home
- Nosebleed: sit forward, pinch the soft part of your nose for 10 minutes without releasing. Do not tilt your head back.
- Small cuts: apply firm pressure with a clean cloth for at least 10 minutes before checking whether it has stopped.
- Avoid aspirin, ibuprofen, and anti-inflammatory painkillers unless your oncology team has approved them — they increase bleeding risk on top of what bevacizumab already causes.
- Tell your team about all supplements you take, including fish oil, garlic capsules, ginger, and turmeric, which can affect how your blood clots.
- Note any new bruising — photograph it and record the date so your team can track whether it is spreading.
- Use a soft-bristled toothbrush if your gums bleed easily, and tell your dentist you are on bevacizumab before any dental work is planned.
When should you call your team today rather than waiting?
Call the same day if a nosebleed takes more than 10 minutes to stop, if bruising is spreading or appeared after very minor contact, or if a wound looks the same or worse after a week of normal care.
Do not wait for your next scheduled appointment if you are seeing more bleeding than before. Same-day contact is the safe default whenever you are unsure — the risk is not in calling, it is in waiting.
If you have recently had surgery, tell your team immediately about any sign that your wound is opening or leaking. Bevacizumab slows the formation of new blood vessels that healing tissue depends on, and wound breakdown needs prompt assessment.
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How do you grade the bleeding you are seeing?
| Feature | Minor — manage at home | Moderate — call your team today | Severe — go to emergency now |
|---|---|---|---|
| Nosebleed | Stops within 10 minutes of firm pressure | Lasts longer than 10 minutes or keeps recurring through the day | Heavy and will not stop |
| Bruising | Small, on limbs, after clear impact | Spreading, unexplained, or after very minor contact | Large, growing quickly, or with significant pain |
| Stool or vomit | No change | Dark or unusual change in stool colour | Black tarry stool, bright red blood, or blood in vomit |
| Abdominal pain | Mild and familiar | Worsening or new discomfort — call the same day | Sudden and severe — go immediately |
| Wound or scar | Healing slowly but progressing | Not progressing, leaking, or reddening at the edges | Opening, actively bleeding, or deeply infected |
| Typically starts | Mild bleeding can appear from the first treatment cycle onward | Can occur at any point during treatment | Can occur at any point, including shortly after a dose or after treatment ends |
Questions families ask about bevacizumab and bleeding
Will bevacizumab affect surgery or a wound from a recent procedure?
Yes, and this is one of the most important things to plan ahead for. Bevacizumab blocks the growth of new blood vessels, which is exactly what healing tissue needs to close properly. Your oncologist will advise on holding the drug before and after any planned surgery or invasive procedure — the timing is a clinical decision that depends on the procedure and your treatment schedule. Tell any surgeon, dentist, or specialist who is planning a procedure that you are on this drug before anything is booked. Never let a procedure happen without both teams aware of your medication.
How would I know if my bowel has perforated?
Bowel perforation typically announces itself with sudden, severe abdominal pain that feels different from anything you have had before — often described as a tearing or stabbing sensation that comes on quickly. The abdomen may become hard and tender to touch, and you may develop a fever or stop passing wind and stool. It is a surgical emergency and does not wait. If you experience any combination of these symptoms, go directly to the emergency department and tell the team immediately that you are on bevacizumab.
Can I take painkillers while on bevacizumab?
Paracetamol is generally considered safer than anti-inflammatory painkillers on bevacizumab — your team will confirm what is right for you specifically. Aspirin, ibuprofen, naproxen, and other NSAIDs affect how platelets work and can increase bleeding risk on top of what bevacizumab already causes. Do not start or continue any painkiller, including over-the-counter ones, without checking with your oncology team first. This also applies to combination cold-and-flu tablets, many of which contain ibuprofen without it being obvious from the brand name.
Do Ayurvedic or herbal remedies affect bleeding risk on bevacizumab?
Some commonly used herbs and supplements affect how your blood clots, and this matters more on bevacizumab than in normal circumstances. Fish oil, high-dose ginger, garlic capsules, turmeric supplements, and aloe vera are among the ones your team will want to know about. This does not mean stopping them without advice — it means telling your treating team exactly what you are taking so they can assess the combination. Never stop a medicine a doctor has prescribed because of something you have read online, and never start a new supplement without asking your oncology team first.
What counts as a wound healing problem I should report?
Report a wound to your team if it looks the same or worse after a week of normal care — not healing, still weeping, reddening at the edges, or beginning to separate. A wound that opens fully, bleeds actively, or shows signs of deep infection needs same-day or emergency assessment. The threshold for reporting is lower on bevacizumab than it would be otherwise, because slow healing is an expected effect of the drug and your team needs to know if it is occurring so they can advise on timing of your next dose.
Did you know?
Bowel perforation is one of the most serious recognised risks of bevacizumab, and it can occur without a long build-up of milder symptoms — which is why sudden severe abdominal pain in a patient on this drug is always treated as an emergency rather than a wait-and-see symptom.
ASCO and NCCN guidance specifically identifies new or sudden abdominal pain in patients on bevacizumab as requiring urgent evaluation, not monitoring at home.
Source: ASCO Clinical Practice Guidelines; NCCN Guidelines for Management of Treatment-Related Toxicities
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Common questions
Frequently asked questions
Is bleeding on bevacizumab dangerous?
It depends on where the bleeding is and how much. Minor bleeding — nosebleeds, small bruises, gum bleeding — is common and manageable at home. Bleeding from the gut or lungs, or any heavy bleeding that will not stop, is a different matter entirely and needs emergency assessment. Bevacizumab works by disrupting blood vessel formation, which affects your body's normal ability to contain bleeding. The most important thing you can do is take any new or worsening bleeding seriously rather than assuming it is trivial until your next scheduled appointment.
Can bevacizumab cause bleeding in the brain?
Bleeding in the brain is a rare but recognised risk, particularly in patients with brain metastases or those taking anticoagulant medicines at the same time. NCCN guidance identifies central nervous system bleeding as one of the more serious potential complications of this drug. Sudden severe headache, confusion, difficulty speaking, weakness on one side of the body, or sudden changes in vision while on bevacizumab should all prompt an immediate call to emergency services — these are not symptoms to assess at home or wait out.
How soon after a dose can bleeding problems appear?
There is no safe window after a dose. Bevacizumab has a long half-life, meaning it stays active in your body for weeks after each infusion. Bleeding events and bowel perforation can occur at any point during treatment and for some weeks after it ends. This is why your team asks you to report symptoms between cycles, not only when you are due for the next infusion. If something new appears mid-cycle, call — do not hold the question until your appointment.
Can I have a dental procedure while on bevacizumab?
Tell your dentist you are on bevacizumab before any invasive procedure is planned, and tell your oncologist at the same time. Simple cleaning carries lower risk than extractions or surgery, but any procedure that cuts into tissue carries added risk because of bevacizumab's effect on wound healing and blood vessel formation. Your oncology team may advise on timing around your treatment cycle. The two teams need to coordinate — never let either proceed without the other knowing.
What should I tell the emergency department if I go in?
Tell them immediately that you are on bevacizumab (Avastin) for cancer treatment, the name of your oncologist and the hospital where you are being treated, and when your last dose was given. If you have a drug card or treatment summary document, bring it or have a family member photograph it on a phone before you leave home. This information helps the emergency team make the right decisions quickly — certain interventions carry added risk on bevacizumab, and the team needs to know before they act, not after.