An Ova and Parasite (O&P) stool test detects intestinal parasites by identifying parasite eggs (ova), cysts, and trophozoites in feces. It screens for protozoa (e.g., Giardia, Entamoeba) and helminths (e.g., Ascaris, hookworm), helping diagnose causes of diarrhea, abdominal pain, or unexplained weight loss. Multiple stool samples are often needed for accurate detection and to guide treatment.

An ova and parasite (O&P) stool exam usually requires up to three separate stool samples collected on different days. Once samples reach the lab, microscopic concentration and staining are typically completed within 24–72 hours; some labs can report same-day. If confirmatory tests or repeat sampling are needed, final results may take up to a week.

Costs vary by country and setting. In the U.S., an ova and parasites (O&P) stool test typically costs $20–$150 depending on lab, location, and whether single or multiple specimens are required. Specialized panels or PCR-based tests may cost $100–$300. Public clinics or insured patients may pay less or nothing after coverage. Contact your provider or local lab for exact pricing.

Ova and parasite (O&P) stool testing has variable accuracy. A single traditional microscopy stool exam can miss infections because parasites shed intermittently; sensitivity is limited. Collecting at least three separate samples and using concentration techniques, antigen detection, or PCR greatly improves sensitivity and specificity for organisms like Giardia and Cryptosporidium. A single negative test does not completely rule out infection—clinical context and repeat or molecular testing may be needed.

Parasitic infections usually cause weight loss, poor appetite or malabsorption rather than true weight gain. Some infections can cause bloating, fluid retention or increased appetite, which might be perceived as weight gain, but actual parasite-driven fat gain is uncommon. If you have unexplained weight changes, abdominal symptoms, or travel exposure, see a healthcare professional — stool and blood tests can diagnose infections and effective treatments are available.

Common foods linked to parasitic infections include raw or undercooked meats (pork, beef, game) that can carry tapeworms and Trichinella; raw or undercooked fish, sushi or ceviche (Anisakis, Diphyllobothrium, liver flukes); raw or unwashed fruits and vegetables contaminated with feces (Giardia, Cryptosporidium, Cyclospora, Toxoplasma); raw shellfish, crabs and crayfish (Paragonimus); and unpasteurized milk or dairy. Proper cooking, washing and pasteurization reduce risk.