Triglyceride levels are measured by a blood test called a complete lipid profile. This chart shows if the results are within the normal range, in milligrams per deciliter (mg/dL):

High triglyceride levels can affect the accuracy of the formula used to calculate LDL levels. Unlike HDL and triglycerides, LDL is not measured directly in most blood tests because it is difficult and expensive to do so. Instead, physicians subtract HDL and one-fifth of triglycerides from the total cholesterol to calculate the LDL.

For example, say a person has a total cholesterol level of 270 and an HDL level, which is measured directly, of 30. The triglyceride level is 250, but this result is divided by 5 to get a score of 50. LDL (270) is calculated by subtracting HDL (30) and triglyceride (50). The LDL level is 190, which is high. This method becomes unreliable when triglyceride levels are above 400. In these cases, LDL must be measured directly.