GUT HEALTH
Why Is My Poop Yellow? Common Causes of Yellow Stool and Diarrhoea
By Georgia Barton-Hague, Registered Nutritionist
By Holly Caske, Registered Nutritionist (ANutr)
Reviewed by Holly Caske, Registered Nutritionist (ANutr)
Reviewed by Georgia Barton-Hague, Registered Nutritionist
Published on 24 September 2025
What does normal stool look like?
The colour of your stool is one of the clearest windows into your digestive health. Normal, healthy stool is typically some shade of brown. This colour comes from bile — a fluid produced by your liver to help digest fats — and from bilirubin, a pigment created as your body breaks down old red blood cells during digestion.
Yellow stool can appear when digestion moves too quickly for bile to fully break down, so the pigments don't have time to darken. It can also be caused by your diet, an infection, or an underlying digestive, liver, or pancreatic issue.
Common causes of yellow poop and diarrhoea
Diet and food colourings — certain foods like turmeric, carrots and yellow food dyes, along with high-fat meals, can tint your stool yellow.
Gut infections and parasites — infections such as giardia can speed up digestion and cause yellow, greasy diarrhoea.
Food intolerances and malabsorption — conditions like coeliac disease or lactose intolerance can prevent proper fat absorption, leading to pale yellow stool.
Gallbladder or bile problems — reduced bile flow, such as from gallstones, means fat isn't broken down properly, resulting in yellow, greasy stool.
Pancreatic conditions — pancreatic insufficiency reduces the digestive enzymes needed to break down fat.
Liver-related conditions — liver issues can affect bile production and cause pale or yellow stool, sometimes alongside jaundice.
The rainbow of poop: what different colours can mean
The colour of your stool can reveal a surprising amount about what's happening inside your digestive system. Here's a quick guide to what different shades might mean:
Brown (normal) — a sign of healthy digestion.
Green — often from fast transit or eating lots of leafy greens.
Yellow — may indicate fat malabsorption or fast transit.
Black or very dark — could indicate bleeding higher in the digestive tract, or simply iron supplements.
Red — could point to lower GI bleeding, or red foods and beetroot.
Pale, clay-coloured, or white — possible bile duct blockage.
If an unusual colour persists for more than a day or two, it's worth seeing a doctor to rule out an underlying issue.
Bright yellow diarrhoea vs. yellow poo: what's the difference?
Yellow poo that is solid or soft is often diet-related and rarely a cause for concern.
Bright yellow watery diarrhoea more often signals an infection, malabsorption, or a bile or gut issue, and tends to move through the gut quickly.
If your symptoms are persistent or severe, it's best to consult a healthcare provider to identify the underlying cause.
When to see a doctor
Persistent yellow watery diarrhoea
Unexplained weight loss
Severe abdominal pain or cramps
Blood in stool, or black, tarry stool
Yellowing of the skin or eyes (jaundice)
Signs of dehydration
Any of these symptoms warrant prompt medical care.
Everyday gut support
Supporting your digestion day to day goes a long way toward keeping your gut — and your stool — healthy. A few simple habits can make a real difference:
Eat a varied, fibre-rich diet
Stay hydrated
Limit high-fat and heavily processed foods
Pay attention to any food triggers
The bottom line
In most cases, yellow stool is temporary and closely tied to what you've eaten or how quickly your body is digesting it. It usually resolves on its own within a day or two. However, if the colour persists or is accompanied by other symptoms, it's worth seeking medical advice to rule out an underlying issue.
Your gut health is worth paying attention to. By listening to your body, eating well, and staying hydrated, you can support a happier, healthier digestive system — and feel your best from the inside out.
References
Smith, J. et al. (2021). "Effects of carbonated beverages on gut microbiota diversity." Journal of Nutrition Science, 12(3), 45-52.
Chen, L. & Patel, R. (2020). "Artificial sweeteners and their impact on the human microbiome." Gut Microbes Review, 8(2), 112-120.
World Health Organization (2022). "Sugar intake guidelines for adults and children."
Nguyen, T. et al. (2019). "Alcohol consumption and intestinal permeability: a systematic review." Alcohol Research, 40(1), 22-31.
Biomel Health Research Team (2023). "The role of fermented drinks in digestive wellness."
Tags
Gut Health
Nutrition
Healthy Swaps
Digestion
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