Triglycerides are a type of lipid that circulates throughout your blood along with cholesterol. Triglycerides are often measured as a part of a lipid profile, which includes values for total cholesterol, LDL cholesterol and HDL cholesterol as well. A lipid profile, which is usually done after an eight- to 12-hour fast, is used to evaluate your risk for heart disease.
Reasons to Fast
There are two reasons that fasting is recommended before a triglyceride test. The first reason is that a meal, especially one high in fat or calories, directly raises your triglyceride levels. According to the Harvard Medical School Family Health Guide, eating within 12 hours of a triglyceride test can raise your triglyceride levels by 20 to 30 percent. Another reason to fast is because it allows a more accurate reading for LDL cholesterol, which is calculated using the fasting triglyceride concentration and fasting HDL concentration.
Fasting Basics and Tips
When you are told to fast before a triglyceride test, the only thing you are allowed to consume is water. Other foods and beverages, especially alcohol, raise your triglyceride levels and may provide an inaccurate reading. To make the eight- to 12-hour fast easier, it may help to schedule your triglyceride test for first thing in the morning. This way, you can eat dinner, go to bed and go straight to your appointment. Pack a lunch or a snack to eat directly after your appointment, as you will likely be hungry.
Triglyceride Levels
A normal fasting triglyceride level is defined as less than 150 mg/dL. If your fasting triglyceride level is between 150 and 199 mg/dL, it is considered borderline high. Triglycerides between 200 and 499 mg/dL are categorized as high and triglycerides of 500 mg/dL or higher are very high. Elevated triglyceride levels indicate an increased risk of heart disease.
Considerations
According to a study published in the "Journal of the American Medical Association" in 2007, a fasting triglyceride test may not be the best way to monitor the risk for atherosclerosis. The study found that fasting triglyceride levels showed little independent relationship in incidence of heart problems, whereas non-fasting triglyceride levels did have an independent relationship. Another study published in "Clinical Chemistry" found that both fasting and non-fasting triglyceride levels were associated with cardiovascular disease risk, but in fasting participants, the association was weaker.
References
- Lab Tests Online; Lipid Profile; March 22, 2011
- Lab Tests Online; Triglycerides; March 22, 2011
- Harvard Medical School Family Health Guide; Making Sense of Cholesterol Tests; February 2005
- "Clinical Chemistry"; Fasting versus Nonfasting Triglycerides and the Prediction of Cardiovascular Risk: Do We Need to Revisit the Oral Triglyceride Tolerance Test?; Paul M Ridker; November 12, 2007
- "Journal of the American Medical Association"; Fasting Compared With Nonfasting Triglycerides and Risk of Cardiovascular Events in Women; Sandeep Bansal; 2007
