The most common symptom of giardiasis is diarrhea. However, although giardiasis is a diarrheal illness, other signs and symptoms include gas, stomach cramps, and abdominal pain. In otherwise healthy people, the symptoms tend to last two to six weeks, with the diarrhea generally improving after a week or so. People who have chronic giardiasis may experience symptoms for months or even years.
When a person becomes infected with the parasite that causes giardiasis (Giardia lamblia), the parasite begins to multiply within the intestines. After one to two weeks (the average is seven days), giardiasis symptoms can occur. This period between becoming infected and the start of symptoms is the "Giardia incubation period."
Giardiasis symptoms may begin gradually or come on all of a sudden. Symptoms can vary among individuals. Some people may be infected with Giardia but have no symptoms; other people may experience severe symptoms.
A Giardia infection can cause a variety of intestinal symptoms. Some common symptoms of giardiasis can include:
- Gas or flatulence
- Abdominal pain
- Greasy stools that tend to float
- Stomach cramps
- Upset stomach or nausea.
These symptoms may lead to weight loss and dehydration.
In otherwise healthy people, giardiasis symptoms may last two to six weeks. The diarrhea can improve after a week or so. Occasionally, symptoms may last longer. These people may have chronic giardiasis, in which the condition keeps recurring (coming back).