How can i tell if i have parasites?

Test: Some symptoms may be indicative of parasites , such as diarrhea, peri-anal itch, elevated level of certain blood cell type ( eosinophil) etc..., but to definitely know if you have parasite is to identify it by specific tests ( stool for ova and parasites, scotch tape test, anti body test and so on), if you think you may be infested with a parasites, tell your doctor about it.

Stool sample: For most of the gastrointestinal parasites a stool sample for ova and parasites would suffice. Would suggest starting with your Primary care doc who can review your symptoms, do a physical exam and decide if such a test would be worth, given context.

Parasites: If you mean intestinal parasites, the best thing to do is to see a doctor with a list of all symptoms and then have your stool examined by an expert in this area.