A triglyceride test, part of a cholesterol panel, is a blood test that measures the levels of triglycerides in the blood. Triglyceride levels may be measured either when a person is fasting or not fasting.

Triglyceride levels in the blood increase after a person eats, therefore, many practitioners believe that a person should fast before taking a triglyceride test.

However, recent research has shown that non-fasting triglyceride tests may be as accurate as fasting tests in certain situations. Experts state that non-fasting triglycerides levels of more than 200 milligrams per deciliter (mg/dL) should be considered high.

The body stores triglycerides in the adipose or fat tissues, but they also move through the bloodstream. Excess calories, especially starchy sugars, are stored as triglycerides. And the body uses triglycerides for cell functions.

Triglyceride levels are usually tested as part of a full fat or lipid profile to help assess someone's risk of developing cardiovascular disease. Also, the blood test can be used to investigate the underlying cause of pancreatitis, a condition where the pancreas is inflamed.

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Triglycerides are a form of fat stored in the body.

A triglyceride test is a blood test that measures blood levels of triglycerides. Blood can be tested either in a fasting or non-fasting state. Because triglycerides are a type of fat or lipid, their levels are checked as part of a blood test called a lipid profile.

Triglycerides in the blood increase after a meal, because they are being sent from the gut through the bloodstream to the adipose tissue for storage.

With a fasting triglyceride test, a person is asked to fast for between 9 and 12 hours before having blood taken and tested. Non-fasting tests do not require a person to fast beforehand.

For the last few years, researchers have been looking at the benefits of non-fasting triglyceride tests. The theory is that for most of the day, levels are what they would be after meals, so a sample taken without fasting could be as useful.

In Europe, the advice changed in 2014, and it is no longer recommended to fast before routine testing.

The American College of Cardiology (ACC) has divided their guidelines for when to use a fasting or a non-fasting test based on the individual. As of 2016, their recommendations are as follows:

  • Evaluating the risk of heart disease in a person not treated for high cholesterol: Non-fasting acceptable.
  • Screening for metabolic syndrome: Non-fasting acceptable.
  • Screening individuals with a family history of inherited cholesterol problems or early onset heart disease: Fasting required.
  • Confirming hypertriglyceridemia or high triglycerides: Fasting preferred.
  • Evaluating pancreatitis: Fasting preferred.
  • Evaluating the risk of heart disease in a person treated for high cholesterol: Fasting preferred.

A non-fasting test can be more comfortable and convenient for the individual and may be safer for people with diabetes, who can experience hypoglycemia or low blood sugar when they have been fasting.

It is recommended that people whose triglyceride or TG levels are found to be abnormally high during a non-fasting test have a fasting test to confirm the result.

The most up-to-date definitions of high triglycerides by the ACC and the American Heart Association (AHA) for adults are as follows:

  • Optimal: Less than 100 mg/dL or 1.1 millimoles per liter (mmol/L).
  • Normal: Less than 150 mg/dL or 1.7 mmol/L.
  • Borderline high: 150–199 mg/dL or 1.7–2.2 mmol/L.
  • High: 200–499 mg/dL or 2.3–5.6 mmol/L.
  • Very high: Greater than 500 mg/dL or 5.6 mmol/L.

For those undergoing a non-fasting test, a result of 200 mg/dL or more is categorized as high. The individual would usually then be asked to have a fasting triglyceride test for a follow-up.

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Those with a family history of high cholesterol should get their triglyceride levels measured.

The most common reason someone might be advised to have their triglyceride levels checked is to help assess their risk of developing cardiovascular disease.

Healthy adults are recommended to have a lipid profile, which includes a triglycerides test, every 4 to 6 years, to evaluate the risk of heart disease.

Testing may be more frequent if the individual has risk factors for heart disease, such as:

  • smoking tobacco
  • being overweight or obese
  • eating an unhealthy diet, such as high in saturated fats, sugar, and alcohol, and low in fruits and vegetables
  • being physically inactive
  • having high blood pressure
  • a family history of severely high cholesterol or premature heart disease
  • pre-existing heart disease
  • diabetes or prediabetes

Triglyceride tests may also be ordered to monitor the success of lipid-lowering lifestyle changes, such as improving diet and increasing exercise, or for checking the effectiveness of drugs, such as fibrates, omega-3s, niacin, or statins.

The ACC and AHA recommend that adults treating high cholesterol and high triglycerides have a fasting lipid profile carried out 4 to 12 weeks after starting treatment. This profile should then be rechecked, as needed, to monitor the effect of lifestyle changes and medications.

Experts stress that the goal in all triglyceride and cholesterol treatment is to lower the risk of heart disease. Regardless of medications, heart experts agree that healthful lifestyle choices are an essential part of reducing that risk.

Here are the current recommendations for healthful lifestyle choices to lower risk of heart disease and lower cholesterol and lower triglycerides:

  • not smoking
  • daily physical activity
  • limiting saturated fats
  • restricting processed sugars
  • limiting alcohol
  • maintaining a healthy weight
  • increasing fruits and vegetables
  • choosing lean proteins, such as soy, fish, nuts, beans, chicken, and turkey

The relationship between triglycerides and cardiovascular disease is not fully understood, but there is growing evidence that high levels of triglycerides in the blood increases the risk of heart problems.

Triglycerides interact with the body in complex ways, and scientists continue to study these interactions. Many studies have shown triglycerides add to inflammation that can increase damage and blockages to blood vessels.

High triglyceride levels can also lead to an inflamed pancreas or pancreatitis, which is a serious medical condition. Pancreatitis can cause severe abdominal pain, which can extend from the upper stomach to the back and can even lead to life-threatening organ failure.

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Regular exercise may help to lower triglyceride levels.

Some medical conditions can contribute to high blood triglyceride levels, including:

  • alcohol use dependency
  • diabetes
  • kidney disease
  • thyroid disease
  • liver disease
  • metabolic syndrome

Some medications can also have the same effect on blood triglyceride levels

In all these cases, doctors will work with the individual to treat the underlying condition or make changes to their medications.

A person can make specific lifestyle choices to reduce their triglyceride levels, including:

  • avoiding smoking
  • getting plenty of regular exercise
  • reducing alcohol intake
  • eating a healthful diet

If TG and cholesterol test results and other health markers suggest someone is at high risk of heart disease, a doctor will likely recommend treatment and a follow-up plan.

Most crucial of all is undergoing lifestyle changes, such as adopting a healthful diet, daily physical activity, and quitting smoking.

A doctor may recommend lipid-lowering medications, such as fibrates, omega-3s, niacin, and statins when triglyceride levels are significantly high. They may then use ongoing TG tests to check the effectiveness of the treatment program.

Triglyceride levels are usually tested as part of a full lipid profile to aid in assessing someone's risk of developing cardiovascular disease. This blood test may also be used to investigate suspected pancreatitis.

Whether fasting should be recommended ahead of a TG test depends on the individual and the reasons for testing.

In Europe, non-fasting TG tests are used for routine screenings. In the United States, heart experts have made specific recommendations on who to test with the different methods.