Loose Stool: Causes in Adults and How It Differs from Diarrhea

Loose stool is a change in the consistency of stool that in itself does not equal a diagnosis. Below is reference information on the criteria for diarrhea, the causes of loose stool in adults, and the tests that help find the cause.

What counts as loose stool and how it differs from diarrhea

Diarrhea is loose, watery stool three or more times a day. In the clinical description the criteria are similar, but with volume: more than two bowel movements per day in which the stool is watery, with a volume of more than 200 milliliters, often with pain around the navel, urgency, and fecal incontinence.

The criteria for diarrhea are three or more times a day or more than two times a day with a volume of more than 200 milliliters; stool that does not meet these criteria is not considered a diagnosis of diarrhea. Frequency per day, volume, duration, and associated signs are taken into account. By duration, a distinction is made between acute diarrhea (up to two weeks), prolonged, and chronic — diarrhea lasting at least four weeks.

What causes loose stool in adults

The most common causes are intestinal infection and food poisoning. Diarrhea is also associated with medications (the side effect is stated in the instructions), irritable bowel syndrome, anxiety, appendicitis, inflammatory bowel diseases, celiac disease, diverticular disease, and radiation therapy in the pelvic area. Other causes are bacteria, viruses (norovirus, rotavirus), and parasites from contaminated food and water, antibiotics, anticancer drugs, magnesium-containing antacids, lactose intolerance, Crohn's disease, and stomach surgery after which food passes through the tract more quickly.

The character of the stool depends on the mechanism: in motor diarrhea, typical of IBS and functional diarrhea, the stool is semi-formed, in small portions, up to 300 milliliters; in exudative diarrhea (inflammation and ulceration of the colonic mucosa) it is loose and scanty, with blood, mucus, and pus.

Loose stool in the morning and once a day

No separate "morning" form of diarrhea is distinguished: time of day is not part of the criteria. What matters is the frequency per day, volume, consistency, and duration.

If loose stool recurs in the morning day after day, the question shifts to duration: diarrhea that persists for several days may be a sign of a more serious problem, and chronic diarrhea (at least four weeks) may be a symptom of a chronic disease. Chronic diarrhea occurs in 7–14% of the world's adult population.

Loose stool without other symptoms

With a viral or bacterial cause, fever, chills, and blood in the stool are possible. Sometimes the cause cannot be found, and if the diarrhea resolves within a few days, a search for the cause is usually not needed.

Diarrhea can lead to dehydration; it is more dangerous for children, older people, and people with weakened immunity.

How to find the cause: which tests are ordered

The scope of testing depends on duration. The doctor examines the patient, clarifies the medications being taken, and if necessary orders a stool or blood test to look for bacteria, parasites, and other signs of disease; if a food reaction is suspected, suggests eliminating certain foods. In chronic diarrhea, additional tests are performed.

• examination and history-taking, including medications being taken;
• stool and blood tests for bacteria, parasites, and other signs of infection;
• a trial elimination of certain foods to check for a food reaction.

When loose stool is a reason to see a doctor

For an adult, the time-based guideline is diarrhea lasting longer than two days. In adults and children, diarrhea usually stops within 5–7 days; persistence beyond seven days is a reason to seek care. Medical attention is sought for signs of dehydration, severe abdominal or rectal pain, a temperature of 38.9 °C or higher, blood or pus in the stool, or black tarry stool.

Loose stool in itself is not a reason to call an ambulance. The numbers 103 and 112 — if an adult has vomiting of blood or vomit that looks like coffee grounds, green vomiting, sudden severe abdominal pain, neck stiffness with pain when looking at bright light, sudden severe headache, gray-blue, pale, or mottled skin, severe difficulty breathing, or confusion.

This material is for reference: it describes signs and tests but does not replace a doctor's consultation — the approach is determined by the doctor after examination.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer