Giardiasis

It spreads by swallowing the parasite in contaminated drinking water, uncooked food washed in contaminated water, swimming water, or by contact with the stool of an infected person or animal, including through unwashed hands, nappy changing and close household contact. It is not caught from sharing a toilet seat alone but is spread when hands or objects carrying microscopic faecal matter reach the mouth.

Giardiasis is one of the more common intestinal parasite infections in the world, especially where water or sanitation is not safe and among young children, nurseries and families. Travellers and people who drink untreated water are also at risk. Some infected people never have symptoms but can still pass the parasite on.

When travelling, including for Hajj and Umrah or visiting rural areas, drink only bottled, boiled or properly treated water, and wash hands before eating. Wash raw vegetables and fruit with safe water.

The doctor asks about travel, water, contacts and symptoms. Diagnosis is usually made by testing a stool sample for the parasite or its proteins or genetic material. Because the parasite is not always passed every day, more than one sample may be needed. In unclear cases a sample of the small intestine lining may be taken during upper endoscopy. Your doctor decides which tests you need.

Good hygiene both helps recovery and stops the infection from spreading to others.

• Wash hands with soap and water after the toilet, after changing nappies, and before preparing or eating food

• Stay at home from work, school or nursery until diarrhoea has stopped, as your doctor advises

• Avoid swimming pools for at least two weeks after diarrhoea has stopped

• Clean toilets, changing areas and shared surfaces; wash soiled clothes and bedding on a hot wash

• Drink only safe water when travelling: bottled, boiled or properly treated

The most important thing is replacing the fluid you lose.

• Drink plenty of fluids; oral rehydration solutions are helpful, especially for children, as advised by a doctor or pharmacist

• Eat small, light meals as your appetite returns

• Some people find milk and fatty foods worsen symptoms for a few weeks after infection; reduce them if so

• Wash fruit and vegetables with safe water and eat food that is well cooked or peeled when travelling

• Breastfed babies should continue to be breastfed; ask a doctor about any other changes in feeding

Antiparasitic medicines clear the infection. Your doctor chooses the right medicine and decides whether the family needs treatment.

• Take the antiparasitic medicine exactly as prescribed and finish the course

• Some of these medicines interact with alcohol; follow the advice on the label and from your doctor

• Check with your doctor in pregnancy, as medicine choices and timing differ

• Children's doses are set by the doctor; never give an adult's medicine to a child

• Do not use anti-diarrhoea medicines without medical advice

Most people do not need any procedure.

• Stool tests to confirm the infection and later to check it has cleared if symptoms continue

• Upper endoscopy with a small bowel biopsy in uncertain or long-lasting cases

• Intravenous fluids in hospital if dehydration is severe

Most people recover completely with treatment, and some recover without it. Symptoms sometimes continue after the parasite has been cleared, such as lactose intolerance (difficulty digesting milk sugar) or irritable bowel symptoms, which usually improve with time. Re-infection is possible if the source is not removed.

• Do I need a stool test, and how will I know it has cleared?

• Which medicine is right for me or my child?

• Should my family or close contacts be tested or treated?

• When can I (or my child) return to work, school or nursery?

• Which signs of dehydration should make me seek urgent care?

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.