There are a variety of tests used to test for parasites but sadly they aren't the most reliable.
Stool samples are the most common form of parasite testing. Stool samples can be taken for inspection under a microscope - but parasites might not be in the samples provided.
Blood testing is also popular but there isn’t such a thing as a blood test that checks for every type of parasite. Blood testing can be used to check for antibodies to a small number of parasites. Blood testing samples are also viewed under a microscope to find visible parasites that reside in the blood.... but it doesn't address parasites found elsewhere in the body.
Sometimes parasites are observed on CAT scans, MRI's & x-rays and are discovered when health care professionals are looking for something else.
And while not a common or cost-effective method for parasite diagnosis, endoscopy can be a great way to reveal parasites depending on where it goes.
Bottom line - if you have symptoms of parasitic infection but tested negative.... I wouldn't rule it out.
