What are the first signs of giardiasis?

Giardiasis is an intestinal infection caused by a microscopic parasite. Symptoms may start after contaminated water, food or contact with infected stool, although the timing can vary. Diarrhoea may be foul-smelling or greasy, and abdominal discomfort, bloating and excess gas can accompany it. Some infected people have mild symptoms or none. These features can resemble other stomach infections, so the pattern and any exposure history help guide assessment.

Drink frequent small amounts of fluid and consider oral rehydration advice from a pharmacist if diarrhoea continues. Wash hands carefully after using the toilet and before preparing food, and avoid preparing food for others while unwell. Arrange a GP consultation if symptoms persist, recur after travel or affect hydration. A clinician may request a stool sample before recommending antibiotic treatment.

Seek prompt medical advice for signs of dehydration such as very little urine, marked dizziness or unusual drowsiness, or for severe abdominal pain, blood in stool, persistent vomiting or a high fever. Young children, older adults, pregnant people and those with weakened immunity may need earlier review. Emergency care is appropriate if someone becomes confused or cannot keep fluids down.

Ask whether stool testing is needed, how to replace lost fluids, when it is safe to return to work or school, and whether household contacts need advice. If treatment is prescribed, ask how to take it and what symptoms should prompt reassessment.