<<Disclaimer: Verify this information before applying it to your situation.>> Rosalie Jalbert asks if " you must be off all antacids, >i.e. PeptoBismal before the tests [for giardia] can be done"?. I've had lots of stool exams done for parasites over the last 20 years and no one has ever suggested that antacids might interfere. According to Markell and Voge's text, Medical Parasitology, Giardia lamblia "is one of the most easily recognized intesinal protozoa." They go on to write (p.74) that "Giardia does not appear consistently in the stools of all patients. Danziger and Lopez (1975) describe three patterns of excretion: high, with parasites present in nearly all stools, low, with small numbers of parasites present in only about 40% of stool specimens; and a mixed pattern with one to two weeks of a high excretion rate alternating with a shorter period of low excretion. With this in mind, it is well to collect specimens at intervals some days apart, if initially they are negative." It is pretty standard practice to submit three stool specimens whenever a parasite infection is suspected. My insurance company recently refused to pay for the two of the three until I got my doctor to send them a "medical justification" for submitting three. > My next question would then be--how long does untreated >giardia stay in your intestine and what effects would it cause? Many people in poor countries such as Mozambique, who have poor access to treatment and clean water, live all their lives with Giardia. I don't know how significant a shortening of potential lifespan might be involved. As for effects, Markell and Voge write (pp.74-75) Biopsy of the jejunum ...reveals in some patients shortening and blunting of the villi, reduction in height of the columnar epithelial cells of the mucosa, and hypercullularity of the lamina propria. In others with severe symptoms, a fairly normal villus architecture is seen. "