There are some parts of the body where a candida infection is hard to diagnose and most practitioners go on med history and symptoms. However, having it in the bladder and mouth, I was able to be diagnosed with a urine and mouth cultures by both a urologist and infectious disease (ID) specialist.
They also took blood, for which I'm waiting on confirmation that it's systemic as the ID specialist felt that it was. The ID specialist will take a med history (mine included insertion of a foley catheter, 12-rounds of Antibiotics , and one round of prednisone in the past year ... all of which can allow candida to grow and thrive.) which help them to further determine your situation. In my case the med history and present symptoms made him feel candida was systemic.
I can only speak for the candida though, I'm not sure how parasites would be diagnosed. Good health to you!!