High triglycerides: what they mean, what causes them and how to lower them

Diet high in refined carbohydrates and sugar

When you consume more calories than your body can use immediately, the liver converts the excess into triglycerides and releases them into the bloodstream for storage in fat cells. This conversion is particularly pronounced with refined carbohydrates, sugar-sweetened drinks, fruit juice, white bread, and highly processed foods. Unlike dietary fat, which enters circulation directly after a meal, excess carbohydrates are converted to triglycerides through a hepatic process that raises fasting levels over time. Cutting refined carbohydrates tends to reduce triglycerides faster than cutting dietary fat in most people.

Alcohol consumption

Alcohol has a direct and potent effect on triglyceride production in the liver. Even moderate alcohol intake raises fasting triglyceride levels in people who are susceptible. For those with borderline or elevated readings, alcohol is often the single most impactful modifiable factor: reducing intake by even half can produce measurable improvements within weeks. People with familial hypertriglyceridaemia are particularly sensitive to alcohol's effect on liver-based triglyceride synthesis.

Insulin resistance and metabolic syndrome

Insulin resistance impairs the body's ability to clear triglycerides from the bloodstream after meals, and it also drives the liver to produce more triglycerides from circulating glucose. Raised triglycerides are one of the five defining features of metabolic syndrome (alongside elevated blood pressure, high fasting glucose, low HDL cholesterol, and excess abdominal fat). If triglycerides are elevated alongside a low HDL reading, this combination is one of the most reliable indirect markers of insulin resistance even when fasting glucose appears normal. The triglyceride-to-HDL ratio is used in research as a surrogate for insulin sensitivity.

Underactive thyroid (hypothyroidism)

Thyroid hormones regulate the enzymes that break down triglycerides. When thyroid output falls, this clearance mechanism slows, and triglyceride levels rise as a consequence. Many people with borderline-high triglycerides are found on fuller testing to have subclinical hypothyroidism, where TSH is mildly elevated but T4 and T3 appear within the normal range. This pattern is reversible with appropriate thyroid support, which is why checking TSH alongside a lipid panel is clinically important when triglycerides are raised.

Obesity and excess visceral fat

Excess body fat, particularly visceral fat stored around the abdomen and organs, is a metabolic driver of raised triglycerides. Visceral adipose tissue releases fatty acids directly into the portal circulation, prompting the liver to produce more triglyceride-carrying VLDL particles. Even modest weight loss of 5 to 10 per cent of body weight can produce clinically significant reductions in triglyceride levels. This makes abdominal circumference a practical early indicator of triglyceride-related metabolic risk.

Inherited (genetic) causes

Primary hypertriglyceridaemia refers to inherited conditions that raise triglyceride levels independent of lifestyle. Familial hypertriglyceridaemia raises triglyceride levels alone, while familial combined hyperlipidaemia raises both triglycerides and LDL cholesterol. Type 3 hyperlipidaemia causes accumulation of both, and familial chylomicronaemia syndrome (a rarer condition) produces severely elevated levels that require specialist management. Genetic causes should be considered when triglycerides are persistently high despite lifestyle changes, when levels are very high at a young age, or when there is a strong family history.

Medications and secondary causes

Several commonly prescribed medications raise triglycerides as a side effect, including beta blockers, oestrogen-containing contraceptives and HRT, certain immunosuppressants, and some antiretroviral drugs used in HIV management. Uncontrolled type 2 diabetes, kidney disease, and liver disease all also impair triglyceride clearance. Secondary causes should be ruled out before concluding that elevated triglycerides are primary or lifestyle-related, which requires a broader set of blood markers than a simple lipid panel.

Standard NHS lipid panels include triglycerides alongside total cholesterol, LDL, and HDL. UK guidance (updated in 2014) no longer routinely requires fasting before a triglyceride test: HEART UK recommends a non-fasting target below 2.0mmol/L. If a non-fasting result is elevated, a fasting test (10 to 14 hours without food) may follow, with a fasting target below 1.7mmol/L. Levels between 4.5 and 9.9mmol/L (fasting) indicate moderate hypertriglyceridaemia. Levels above 10mmol/L carry a significant risk of acute pancreatitis.

The limitation of testing triglycerides in isolation is that they are only one piece of the lipid picture. A meaningfully higher triglyceride reading alongside a low HDL reading, for example, tells a very different story about cardiometabolic risk than either marker alone. Similarly, triglycerides tested without HbA1c or fasting glucose miss the metabolic context that often explains why they are raised in the first place.

A more complete approach measures the full cardiovascular risk picture alongside the factors most likely to be driving elevated triglycerides:

Triglycerides measure the fat circulating in the blood. Persistently elevated levels contribute to plaque formation and increase cardiovascular risk, particularly when combined with low HDL.

HDL cholesterol is inversely related to triglycerides in most people: as triglycerides rise, HDL falls. The triglyceride-to-HDL ratio is a recognised surrogate marker for insulin resistance and cardiovascular risk.

LDL cholesterol and total cholesterol provide the broader lipid picture. Elevated triglycerides often accompany elevated LDL, and addressing one frequently helps the other.

ApoB measures the number of atherogenic lipoprotein particles more directly than LDL alone. It is increasingly used in cardiovascular risk assessment for people with raised triglycerides, where LDL can be misleadingly low.

HbA1c and fasting glucose identify whether insulin resistance or uncontrolled blood sugar is driving the triglyceride elevation.

TSH rules out hypothyroidism as a secondary cause, which is clinically important and frequently overlooked.

CRP reflects systemic inflammation, which both accompanies and is worsened by persistently raised triglycerides.

If your GP has already tested triglycerides and they are elevated, they will typically advise lifestyle changes first, with medication considered if levels remain high after three to six months. Home testing is most useful for people who want to track their levels between NHS appointments, understand the full metabolic context around their triglyceride reading, or investigate why their levels are not responding to lifestyle changes as expected.

Dietary carbohydrate and sugar reduction

The most consistently effective dietary intervention for high triglycerides is reducing refined carbohydrates and added sugar, rather than simply cutting dietary fat. Studies show that replacing refined carbohydrates with protein or unsaturated fats produces rapid reductions in fasting triglyceride levels. Practically, this means reducing white bread, pasta, rice, sugary drinks, fruit juice, and ultra-processed snacks, and increasing vegetables, legumes, whole grains, and quality protein sources. Tracking biomarkers before and after dietary changes is the most reliable way to know what is actually moving the needle for your biology specifically.

Omega-3 fatty acids from oily fish

Omega-3 fatty acids found in oily fish (salmon, mackerel, sardines, herring, anchovies) directly reduce the liver's production of VLDL particles, lowering circulating triglycerides. Regular consumption of two to four portions of oily fish per week has been shown to reduce triglycerides by 15 to 30 per cent in some studies. Prescription-strength omega-3 preparations are available for severe hypertriglyceridaemia, though over-the-counter supplements at standard doses have more variable effects.

Alcohol reduction

For people with elevated triglycerides, reducing alcohol is often the most impactful single lifestyle change. Alcohol stimulates hepatic VLDL production and impairs triglyceride clearance through multiple mechanisms. Even reducing intake from moderate to low levels can produce measurable improvement within two to four weeks, which makes it a useful test: if triglycerides drop significantly after reducing alcohol, that identifies a clear causal pathway worth addressing consistently.

Regular aerobic exercise

Aerobic exercise increases the activity of lipoprotein lipase, the enzyme that clears triglycerides from the bloodstream. Studies show that regular moderate-intensity exercise (150 minutes per week or more) reduces fasting triglycerides by an average of 10 to 20 per cent. The effect is dose-dependent and cumulative: the more consistently exercise is maintained, the greater and more sustained the reduction. High-intensity interval training (HIIT) produces particularly acute reductions in postprandial triglycerides.