High triglyceride levels are most often caused by eating more calories than your body burns, especially from sugar, refined carbohydrates, and alcohol. A fasting level below 150 mg/dL is considered healthy, while anything from 200 to 499 mg/dL is classified as high and 500 mg/dL or above is very high. But diet is only part of the picture. Insulin resistance, certain medications, thyroid problems, kidney disease, genetics, and even pregnancy can all push triglycerides up.
How Sugar and Refined Carbs Raise Triglycerides
Your liver is the central player here. When you eat more sugar or starch than your body needs for immediate energy, your liver converts the excess into fat in the form of triglycerides. This process, called de novo lipogenesis, is especially aggressive with fructose. Unlike glucose, fructose is processed almost entirely in the liver and skips the normal metabolic “speed limit” that slows down glucose processing. The result: fructose floods the liver’s fat-making machinery with raw materials far more efficiently than other sugars.
Sugary drinks are a particular problem. Fructose- and sucrose-sweetened beverages ramp up new fat production in the liver without increasing the rate at which that fat gets exported and cleared from the blood. This means fat accumulates in the liver itself while triglyceride levels rise in your bloodstream. A diet high in sugar relative to fat also suppresses your body’s ability to burn stored fat for energy, compounding the effect. So it’s not just that sugar creates new fat; it also blocks the burning of existing fat.
Refined carbohydrates like white bread, pastries, and white rice behave similarly because they break down into glucose rapidly, triggering the same liver pathways. Overeating in general raises triglycerides, but calorie-for-calorie, sugar and refined starches are more potent triggers than protein or dietary fat.
Alcohol’s Double Effect on the Liver
Heavy drinking raises triglycerides through two simultaneous mechanisms. First, alcohol blocks the liver’s ability to burn fat. It does this by shutting down key enzymes that control fat oxidation. When these enzymes are suppressed, a compound called malonyl-CoA builds up. Malonyl-CoA serves as both a building block for new fat and a stop signal that prevents existing fat from entering the cell’s energy furnaces. So the liver starts making more fat while simultaneously losing its ability to burn the fat it already has.
Second, alcohol impairs the liver’s ability to package and export fat efficiently. A protein needed to assemble triglyceride-carrying particles (called VLDL) for export into the bloodstream decreases in alcohol-exposed livers. The net effect is fat accumulating in liver cells and triglycerides rising in the blood. Even moderate drinking can nudge triglycerides upward in some people, but heavy or binge drinking produces the sharpest spikes.
Insulin Resistance and the Vicious Cycle
Insulin resistance is one of the most common drivers of persistently high triglycerides, and it often goes hand in hand with type 2 diabetes, prediabetes, and excess weight around the midsection. Normally, insulin tells fat cells to hold on to their stored fat. When cells stop responding to insulin properly, fat cells release more free fatty acids into the bloodstream. Those fatty acids travel to the liver, which converts them into triglycerides and ships them back out.
This creates a feedback loop. High triglyceride levels themselves worsen insulin resistance in muscle and other tissues, which causes even more fatty acid release, which drives triglycerides higher still. It’s a vicious cycle that helps explain why people with poorly controlled blood sugar often have stubbornly elevated triglycerides, and why improving insulin sensitivity through weight loss, exercise, or medication can bring levels down significantly.
Medical Conditions That Raise Triglycerides
Hypothyroidism
Thyroid hormones help regulate how quickly your body clears triglycerides from the blood. In hypothyroidism, this clearance can slow down, particularly in people who also carry extra weight. Obese patients with an underactive thyroid tend to overproduce triglyceride-rich particles in the liver while clearing them more slowly than people of similar weight with normal thyroid function. In leaner hypothyroid patients, triglycerides often remain normal, which is why the combination of low thyroid and excess weight is especially problematic. Treating the thyroid condition typically improves lipid levels.
Chronic Kidney Disease
The kidneys play a supporting role in fat metabolism that most people don’t think about. Chronic kidney disease impairs the enzymes responsible for breaking down triglyceride-rich particles in the blood, slowing lipid clearance and allowing triglycerides to accumulate. As kidney function declines, this effect becomes more pronounced, and the elevated triglycerides may in turn accelerate further kidney damage.
Medications That Can Be a Factor
Several commonly prescribed drugs can raise triglycerides as a side effect. Thiazide diuretics, frequently used for high blood pressure, can cause a temporary increase in triglycerides and LDL cholesterol, particularly at higher doses. Smaller doses are less likely to have this effect. Older beta blockers like propranolol, atenolol, and metoprolol can also nudge triglycerides up while lowering HDL (“good”) cholesterol. This side effect is more pronounced in people who smoke. Newer beta blockers are less likely to affect lipid levels.
Corticosteroids, certain acne medications, estrogen therapy, and some immunosuppressants can also elevate triglycerides. If your levels have risen since starting a new medication, that connection is worth exploring with your prescriber, though you should never stop a medication on your own.
Genetics and Inherited Causes
Some people have high triglycerides despite a healthy lifestyle, and genetics are often the explanation. The most common genetic pattern is polygenic, meaning multiple small-effect gene variants combine to raise triglyceride levels. This is sometimes called multifactorial chylomicronemia syndrome, and it accounts for the vast majority of genetically driven severe cases. The severity varies widely depending on which gene variants a person carries and how they interact with diet, weight, and other factors.
A rarer condition called familial chylomicronemia syndrome (FCS) is caused by inheriting two defective copies of genes involved in triglyceride breakdown. FCS represents only about 1% to 2% of patients with severe hypertriglyceridemia. People with this condition can have triglycerides above 1,000 mg/dL even with careful dietary management, because their bodies lack the enzymes needed to clear fat from the blood efficiently. Fasting triglycerides at or above 1,000 mg/dL are found in roughly 0.1% to 0.2% of the general population.
Pregnancy and Hormonal Changes
Triglycerides naturally rise during pregnancy due to hormonal shifts that support fetal development. Levels climb progressively and peak during the third trimester. Despite this expected increase, normal triglycerides during pregnancy are still considered to be 150 mg/dL or less. Women who enter pregnancy with already elevated levels, or who have underlying insulin resistance or genetic predisposition, may see triglycerides climb high enough to pose health risks, including a rare but serious risk of pancreatitis.
Why Very High Levels Are Dangerous
Moderately elevated triglycerides contribute to cardiovascular risk over time, but very high levels carry an additional, more immediate danger: acute pancreatitis. The risk starts climbing once triglycerides exceed 500 mg/dL and increases sharply above 1,000 mg/dL. At levels above 1,000 mg/dL, roughly 5% of people will develop an episode of acute pancreatitis. That risk jumps to 10% to 20% when levels exceed 2,000 mg/dL. Pancreatitis caused by extreme triglyceride levels is a medical emergency, which is why levels above 500 mg/dL are typically treated more aggressively than borderline elevations.