High cholesterol is usually caused by high cholesterol diet, hypothyroidism and other factors. Low triglycerides usually have no special cause and are generally not harmful to health. 1. High cholesterol diet: Eating high cholesterol foods, such as animal offal, for a short period of time before the test or for a long period of time may lead to high cholesterol. High cholesterol foods should be avoided before the test to minimize the effect on the test result. High cholesterol diet should be avoided in daily diet. 2. Hypothyroidism: In hypothyroidism, the metabolism is slowed down, which will lead to slower metabolism of cholesterol and other substances in the blood, thus causing high cholesterol. Patients with hypothyroidism will have symptoms such as fatigue and drowsiness, and less exercise, which may also lead to low cholesterol. If you exclude the reason that the diet before the test affects the test result, you should seek medical attention to clarify the cause with the assistance of your doctor.