Diagnosis of triglyceride level requires a laboratory test to measure the amount of triglycerides in your blood. When you ingest calories, the body uses them for immediate energy. But, excess calories which are not used are stored in the fat cells in the form of triglycerides. This is stored with the intention of using it in future whenever required. Thus, from this you can understand that more calorie intake can make the level of triglycerides high.
The following tests will diagnose the levels of triglyceride

Blood test is done in this manner. Blood is taken from the vein for the purpose of testing. Normally elbow part is used to draw the blood. The site is cleaned and the area around is wrapped with an elastic band so that the area gets the required pressure and vein gets swollen with blood. This makes the blood drawing task simpler. Blood is drawn inserting needle in the vein. And blood is collected in the tube attached to the needle. Then a bandage is placed on the site so that if there is any bleeding, it stops.

The report of this test will reveal the levels of triglycerides. Your health care provider will see the report and tell you what steps are required to be taken, if the levels are high, low or proper.