saudigastro.com/patients/giardiasis
Category
Common
Red flags
5
This article is educational and does not replace your doctor's advice. Seek urgent care for any red-flag symptoms.
What is it?
Giardiasis (say "jee-AR-dye-uh-sis") is an infection of the small intestine with a microscopic parasite called Giardia lamblia (also known as Giardia intestinalis or duodenalis). The parasite lives in the gut of people and animals and passes out in stool in a hardy form (a cyst) that can survive for a long time in water and the environment. When swallowed, it settles in the small intestine and irritates its lining, so absorption of fat and sugars is reduced.
How common is it?
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.
Why does it happen?
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.
Symptoms
- Watery or greasy, foul-smelling diarrhoea
- Gas, bloating and belching with a sulphur-like taste
- Stomach cramps and discomfort
- Nausea and loss of appetite
- Tiredness and weight loss if it lasts for weeks
- Symptoms usually start one to two weeks after infection and may last for weeks
- Poor growth in children if it continues for a long time
Red flags — seek urgent medical care
Signs of dehydration: very dry mouth, dizziness, passing very little urine, sunken eyes, or fainting
You may need fluids through a vein. Go to the emergency department.
A baby or young child with diarrhoea who is drowsy, feeding poorly, has no wet nappies for hours, a sunken soft spot on the head, vomiting, or a fever
Babies and young children can become dehydrated quickly. A baby or child needing urgent care must be seen immediately: go to the emergency department now. Do not give home remedies or anti-diarrhoea medicines unless a doctor says so.
Blood in the stool, high fever, or severe belly pain
This is not typical of giardiasis and suggests another infection or condition. See a doctor urgently.
Diarrhoea lasting more than about two weeks, or ongoing weight loss
Needs testing and treatment, and other causes should be ruled out. See a doctor.
Pregnancy, a weakened immune system, or illness such as HIV or immune deficiency with ongoing diarrhoea
Infection can last longer and treatment choices differ, so be seen early.
How is it diagnosed?
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.
Outlook — what to expect
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.
Treatment
Habits & Lifestyle
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
Diet
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
Medications
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
Procedures & Surgery
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
Living with the condition
- Wash hands and keep up hygiene for a while to avoid passing it on to family members
- If symptoms continue after treatment, see your doctor, as other causes or re-infection are possible
In the Saudi context
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.
Questions to ask your doctor
Save this list or print it before your appointment — doctors appreciate prepared patients.
- 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?
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Status: Approved for publication by SGA; individual clinician review is ongoing · Published 24/04/2026
For general education only; it does not replace your doctor’s advice. Individual clinician review of this guide is ongoing. SGA clinician? Review this guide