Giardia can cause acute, chronic, or asymptomatic infections. Acute Giardia causes watery diarrhea usually within 1-2 weeks of acquiring the parasite. People with Giardia tend to feel quite fatigued, and along with diarrhea suffer from bloating, abdominal cramps, nausea, and flatulence (farting). Chronic infection with Giardia will result in persistently loose stool, fatigue, abdominal cramps, bloating, and weight loss. About 15% of people with Giardia have no symptoms at all, but shed the parasite in their stool.

Giardia is diagnosed by looking for the parasite under the microscope. If an intestinal parasite is suspected, your doctor will give you a small container to collect some of your loose or watery stool. The sample is then sent to the lab for examination.