Giardia is an intestinal parasite that causes diarrhea. It can be transmitted in contaminated food and water, and can also be transmitted by rimming.

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.

Giardia is usually treated with an antibiotic called metronidazole (Flagyl) given two or three times a day for 7 days. Metronidazole can give you a metallic taste in your mouth and you must not drink alcohol while you are taking it. Alcohol mixed with metronidazole will make you vomit. Sexually, Giardia can be transmitted by rimming, so be aware. If you develop diarrhea, have your stool tested.