Blood in Your Stool: What Can Cause It and When Should You Get It Checked?

What causes blood in your stool? 

Common causes include: 

• Haemorrhoids

• Anal fissures 

• Bowel polyps 

• Colorectal cancer 

• Bowel inflammation or inflammatory bowel disease 

Bright red blood often comes from the lower bowel, rectum or anus and may be caused by haemorrhoids or an anal fissure. However, new or persistent bleeding should be assessed rather than assumed to be haemorrhoids. 

What about dark or black stools? 

Bleeding higher in the digestive tract can make stools appear very dark or black. Foods, iron supplements and some medications can also change stool colour. 

Seek medical advice if your stool becomes unexpectedly black or tar-like without an obvious explanation. 

When should rectal bleeding be investigated? 

Speak with a healthcare professional if bleeding is persistent, recurring or unexplained, particularly if accompanied by: 

• Changes in bowel habits or stool appearance 

• Abdominal pain 

• Unexplained weight loss 

• Fatigue or iron deficiency anaemia 

Heavy bleeding, dizziness, fainting, or feeling acutely unwell requires urgent medical attention. 

Will I need a colonoscopy? 

Not everyone with rectal bleeding needs a colonoscopy. Your symptoms, age, family history,  and other risk factors will help determine the most appropriate investigation. 

If recommended, a colonoscopy allows a specialist to examine the large bowel, identify conditions such as inflammation, polyps and colorectal cancer, and remove polyps or take tissue samples where necessary. 

Intus provides specialist colorectal assessment and colonoscopy services, with referrals reviewed to ensure appropriate investigation and follow-up care.