Tapeworms, a class of parasitic flatworms, infect the digestive tracts of humans and animals. They are usually transferred to a body through food or water contaminated with tapeworm eggs or cysts. Tapeworms can develop in the intestines and live for several years. There are several ways you can test for tapeworms.

Blood Test

One of the simplest ways to test for tapeworms is to get a blood test. Though a blood test cannot directly verify the presence of tapeworms, it can analyze indicators that change if tapeworms are present. For example, an unexplained defiance of vitamin B12 could indicate tapeworms because they are known to feast on that vitamin. Since vitamin B12 also helps red blood cells, if you're suffering from tapeworms, you may be anemic as well, which will show on a blood test.

Symptom Test

The easiest test for tapeworms is knowing if you have the symptoms. While this is not a fail-proof test, if you show the symptoms, you'll know whether to seek further testing. Tapeworms cause great abdominal discomfort, so much so that you will experience both diarrhea and constipation. As a result of these intestinal problems, you will also lose a considerable amount of weight in a short time period. If these symptoms occur for sometime, make an appointment with your doctor.

Stool Test

Sometimes it is possible to see tapeworms or their eggs in your stool. You can do this test at home---if you have the stomach for it---or at the doctor's office. The upside to having it done at the doctor's office is that he can look at stool samples under microscopes to identify very tiny eggs or portions of a tapeworm. If the eggs are large enough or the tapeworms long enough, you will see them easily in the stool after a bowel movement---but cases like those are not very common.

MRI or CT Scan

MRI and CT scans are most beneficial because, unlike the other tests, these scans show if you have cysticercoids or a tapeworm infection in your nervous system. Because these scans can take three dimensional pictures of the insides of your central nervous system, they can find cysts or tapeworms lurking in dangerous places. Ultrasound scans have also been used to find cysts, but ultrasounds are less effective than CT scans or an MRI.

Source:

Mayo Clinic: Tape Worm Infection

Mar Vista Animal Medical Center: the Common Tapeworm