High triglycerides: what they are, why they matter and how to lower them

Triglycerides are a combination of three fatty acids and glycerol. HEART UK describes them as our main source of energy, with two supplies: one from the diet and one made by the liver. Fats we eat, such as those in meat, dairy products and cooking oils, are absorbed by the intestines and carried in the blood to the tissues to be used for energy or stored for later. The liver makes its own supply, which is carried in a different type of particle called VLDL.

Triglycerides are different from cholesterol, although both are measured in the same blood test and both travel in the blood in lipoprotein particles. The NHS notes that a cholesterol test can measure total cholesterol, HDL and non-HDL cholesterol, and HEART UK advises that triglyceride levels should be measured when you have a cholesterol test because they also contribute to your risk of heart and blood vessel disease.

HEART UK says that we should aim for a non-fasting triglyceride level below 2.0 mmol/L. If a doctor has asked you to fast, usually for 10 to 14 hours, the level should be below 1.7 mmol/L. The fasting number is lower because only the triglycerides made by the liver are measured, not those that come from food.

National UK guidelines no longer recommend a fasting test, so most people have their blood taken without having to go hungry. The NHS says it makes little difference to cholesterol levels whether you have eaten before the test.

A single high reading should be put in context. Triglycerides vary with recent meals, alcohol and illness, and your GP will look at the whole lipid profile along with your age, blood pressure and health conditions to estimate your overall cardiovascular risk, sometimes with a QRISK score.

HEART UK divides causes into primary and secondary. Primary causes are inherited conditions, such as familial hypertriglyceridaemia, familial combined hyperlipidaemia, type 3 hyperlipidaemia and the rarer familial chylomicronaemia syndrome, in which levels are extremely high. Some people have a combination of inherited and other factors.

Secondary causes are the many other things that influence levels. They include a sedentary lifestyle, an unhealthy diet particularly one high in saturated fats and added sugars, and alcohol, to which some people are very sensitive even in small amounts. Medical conditions include kidney disease, non-alcoholic fatty liver disease, gout, pregnancy and an under-active thyroid. Medicines that can raise triglycerides include some diuretics, steroids, oral oestrogen therapy, retinoids and retrovirals.

Because there can be several causes at once, HEART UK stresses that doctors should investigate all the potential causes so that treatment can be started. Tell your GP about every medicine you take, including those you buy yourself.

HEART UK says high triglycerides contribute to the risk of heart disease and other diseases of the heart and blood vessels. They are particularly important when they occur with low HDL cholesterol, a pattern often linked with premature heart disease. This pattern often occurs in people who are very overweight, especially around the middle, who have type 2 diabetes or who have metabolic syndrome.

Very high levels carry a separate and more immediate danger. HEART UK says they can cause serious conditions such as pancreatitis, which is inflammation of the pancreas. Pancreatitis causes severe tummy pain and needs urgent medical assessment, so use NHS 111, or 999 if the pain is severe.

As the NHS notes for cholesterol in general, high levels usually cause no symptoms, so the only way to find out is a blood test.

HEART UK says diet and lifestyle changes tend to have a big impact. The measures it lists include:

• Keeping to a healthy weight and shape, as carrying weight around the middle can raise triglycerides.

• Being physically active, aiming for at least 150 minutes a week at moderate intensity.

• Replacing saturated fats with unsaturated fats, choosing wholegrain foods and cutting down on added sugars.

• Eating plenty of fruit and vegetables and two portions of fish a week, one of them oily.

• Limiting alcohol to no more than 14 units a week, and less if you are very sensitive to it.

If lifestyle changes do not lower triglycerides enough, or an inherited condition is diagnosed, HEART UK says medication may be needed. Statins are usually the first line of treatment, and cholesterol specialists may also prescribe fibrates and omega 3 acid ethyl esters. The NHS says statins are the most common medicine for high cholesterol and are usually taken for life.

The usual route is through your GP, who can arrange blood tests and refer to a lipid specialist if levels are very high or an inherited condition is suspected. Private cholesterol or triglyceride testing is available, but results are most useful when interpreted by someone who also knows your history, medicines and other risk factors.