Chronic diarrhoea is common and mostly due to diarrhoea predominant irritable bowel syndrome (IBS-D). IBS-D affects about 11% of the population, however up to a third of these patients actually have bile acid diarrhoea (BAD). There are, therefore, more than one million sufferers of BAD in the UK. BAD is caused by small bowel malabsorption of bile acids and the increased bile acids in the large intestine cause diarrhoea. Once diagnosed, the treatment of BAD is simple and effective. BAD, however, is often not diagnosed because of a lack of easily available and reliable diagnostic methods. In the United Kingdom, the radiolabelled 23-seleno-25-homotaurocholic acid test (SeHCAT) is the gold-standard method of diagnosis. SeHCAT, however, is expensive, inconvenient to the patient, involves radiation exposure and has limited availability. As such, a laboratory biomarker is desirable. This review briefly discusses the pathophysiology and management of BAD and critically evaluates methods for its diagnosis, including serum 7α-hydroxy-4-cholesten-3-one, faecal bile acid measurement, serum fibroblast growth factor 19, urine-2-propanol, and the 14C-glycocholate breath and stool test.