Nonfasting vs. fasting triglycerides

Triglycerides are lipids. They are a main component of fat and are used to store energy. They circulate in the blood so that your body can easily access them.

Your blood triglyceride levels rise after you eat food. They decrease when you’ve gone a while without food.

To check for abnormal triglyceride levels in the blood, your doctor will often use a cholesterol test. This test is also called a lipid panel or lipid profile. Triglycerides can be measured after fasting or when you’re not fasting. Typically for a fasting triglyceride test, you’ll be asked to go without food for 8 to 10 hours. You can drink water while in a fasting state. Your nonfasting triglyceride levels are typically higher than your fasting levels. They can vary greatly depending on how recently you’ve consumed dietary fat.

What to expect during a test for triglycerides

Your doctor can measure your triglyceride levels using a simple blood draw. The process is the same if the test is measuring your fasting or nonfasting triglyceride levels. If you’re doctor wants to measure your fasting triglyceride levels, they will likely instruct you to fast for a given amount of time. They may also ask you to avoid certain medications.

If the test is measuring nonfasting triglycerides, there are typically no dietary restrictions. However, your doctor may request that you avoid eating a meal that’s unusually high in fat prior to the test.

Do I have to fast?

Doctors have traditionally tested triglyceride levels under fasting conditions. This is because triglyceride levels rise for several hours after a meal. It can be easier to get a baseline for your triglycerides when they’re tested in a fasting state because your last meal won’t affect the results. In the last decade, research has shown that nonfasting triglyceride levels can be good predictors for certain conditions. This is especially true for those related to heart disease.

Your doctor may take a few factors into account when deciding whether to measure fasting or nonfasting triglyceride levels. These may include:

  • your current medical conditions
  • any medications you’re currently taking
  • what conditions you’re being tested for

You should talk to your doctor about whether to fast before a triglyceride level test.

Testing triglyceride levels is recommended for adults starting at age 45 for women and 35 for men. Testing may begin as early as 20 years old or younger for people with:

  • diabetes
  • high blood pressure
  • obesity
  • smokers
  • a family history of early heart disease

The frequency of testing depends on results from past tests, medications, and overall health.

This test is usually included as part of a cholesterol test. The results of these tests, along with other factors such as smoking status, blood pressure, and blood sugar, can help your doctor determine your 10-year risk of heart disease or stroke.

Major European medical associations now recommend using nonfasting triglycerides as a tool for determining your risk for heart disease. A nonfasting test is often more comfortable and easier because you don’t have to avoid eating. It can also decrease risk of extremely low blood sugar in people with diabetes. In the United States, fasting triglyceride level tests are often still performed. However, more American physicians are starting to follow the European guidelines. There is still a role for fasting cholesterol testing when nonfasting results are abnormal.

What do my levels mean?

Your test results can help your doctor identify your potential risk for heart disease or other conditions. Your doctor will use those results to help establish a prevention plan to reduce your risk. The following are some definitions of abnormal triglyceride levels from the American College of Cardiology:

TypeResultsRecommendation
nonfasting levels 175 mg/dL or higherabnormal result; should be followed up with a fasting triglyceride level test
fasting levels500 mg/dL or highersignificant and severe hypertriglyceridemia, which often requires treatment

Risk factors and complications

High blood triglycerides can be a risk factor for heart disease. It’s unclear whether triglycerides can cause the buildup of plaque in your arteries that’s associated with many types of heart disease. At extreme levels of 1000 mg/dL or more, blood triglycerides can cause acute pancreatitis.

Elevated triglyceride levels can be a sign of metabolic syndrome. Metabolic syndrome is a collection of conditions that include:

  • an excessively large waistline, which is defined as greater than 35 inches in women or 40 inches in men
  • elevated blood pressure
  • elevated blood sugar
  • low HDL, or “good,” cholesterol
  • elevated triglycerides

Each one of these conditions carries risks and complications of its own, and all can be linked to the development of heart disease. Type 2 diabetes, which is characterized by high blood sugar and resistance to the hormone insulin, is also often associated with elevated triglycerides. Other causes of elevated triglyceride levels are:

  • hypothyroidism, which is caused by a deficient thyroid gland
  • liver or kidney disease
  • regular alcohol use
  • a variety of genetic cholesterol disorders
  • some autoimmune diseases
  • certain medications
  • pregnancy

Treatment and next steps

After confirming that you have elevated blood triglycerides, your doctor may suggest various options depending on the level of triglycerides in your blood and other risk factors you might have. Your doctor will likely test for other conditions that could be secondary causes of high triglyceride levels. In many cases, lifestyle and diet changes may be enough to manage the condition.

If your triglyceride levels are very high or your doctor is concerned about your risk for heart disease or other complications, they may prescribe medications such as statins. Statins can help to lower blood lipid levels. Other medications called fibrates, such as gemfibrozil (Lopid) and fenofibrate (Fenoglide, Tricor, Triglide), also have an important role in the treatment of high triglycerides.

Learn more: How do statins work? »

Outlook

Nonfasting triglyceride levels are gradually becoming accepted as an effective and simpler option for the screening of triglyceride levels. Both fasting and nonfasting triglyceride levels can be used to determine your risk of heart disease and various other conditions. Before having a triglyceride test talk to your doctor about whether they want you to fast. It’s important to let them know if you did or did not fast, as this can affect the way they use your results.

Tips to lower your levels

In many cases, it’s possible to control and even reduce your triglyceride levels through lifestyle changes:

  • exercise regularly
  • lose weight if you’re overweight
  • stop using tobacco products
  • reduce your alcohol intake if you drink
  • eat a balanced diet, and reduce your consumption of overly processed or sugary foods

Learn more: The practical 12-step guide to breaking up with sugar »