High cholesterol results from a combination of what you eat, how active you are, your genetics, and sometimes other medical conditions or medications. For most people, no single factor is responsible. Total cholesterol above 200 mg/dL or LDL cholesterol above 130 mg/dL is generally considered elevated, though your overall cardiovascular risk matters more than any one number.
How Diet Raises Cholesterol
Saturated fat is one of the most direct dietary drivers of high LDL (“bad”) cholesterol. When you eat a lot of saturated fat, your liver reduces the number of receptors it uses to pull LDL particles out of your bloodstream. With fewer receptors doing cleanup, LDL accumulates. Foods high in saturated fat include red meat, full-fat dairy, butter, and coconut oil.
Sugar plays a less obvious but significant role. Fructose, found in table sugar, sweetened drinks, and many processed foods, gets processed almost entirely by the liver. There, it activates a fat-production pathway that converts sugar into new fat molecules. The liver packages these fats into particles called VLDL, which eventually become LDL in your bloodstream. Glucose amplifies this effect by enhancing fructose absorption in the gut and providing the insulin signal that ramps up fat production even further. This is why people who drink a lot of sugary beverages often have elevated triglycerides and LDL even if their overall diet isn’t particularly high in fat.
Trans fats, still present in some fried and processed foods, raise LDL while simultaneously lowering HDL (“good”) cholesterol, making them especially harmful.
Genetics and Familial Hypercholesterolemia
Some people inherit genes that make high cholesterol almost inevitable regardless of lifestyle. The most well-known genetic cause is familial hypercholesterolemia (FH), which affects roughly 1 in 200 to 1 in 250 people worldwide, making it the most common inherited cardiovascular condition. Most people with FH don’t know they have it.
FH is caused by mutations in genes that control how your body removes LDL from the blood. The most common mutations affect the LDL receptor gene itself, which means the liver can’t efficiently grab and clear LDL particles. Mutations in other genes, including ones that affect how LDL binds to its receptor or how quickly receptors are broken down, produce similar results. People with FH from one parent typically have LDL levels of 190 mg/dL or higher starting in childhood. Those who inherit mutations from both parents can have LDL above 400 mg/dL and face serious heart disease risk before age 20.
Even without FH, your genetic makeup influences where your cholesterol levels naturally sit. Dozens of common gene variants each nudge LDL or HDL slightly higher or lower, and their combined effect explains why two people eating the same diet can have very different cholesterol numbers.
Physical Inactivity and Sedentary Habits
Regular physical activity has a well-documented effect on cholesterol. Active people tend to have lower LDL, lower triglycerides, and higher HDL compared to sedentary individuals. Exercise increases the concentration of large, protective HDL particles while reducing the smaller, less helpful ones. Sedentary behavior shows the opposite pattern: more time spent sitting is associated with higher LDL and lower HDL.
The mechanism involves an enzyme called lipoprotein lipase, which breaks down triglyceride-rich particles in your blood. Physical activity stimulates this enzyme. When you’re inactive for long stretches, the enzyme’s activity drops, triglycerides accumulate, and your liver produces more small, dense LDL particles, the type most strongly linked to artery damage.
Smoking and Alcohol
Smoking raises total cholesterol, LDL, and triglycerides while lowering HDL in a dose-dependent way: the more you smoke, the worse the effect. Beyond shifting the numbers, smoking changes the quality of your cholesterol. Free radicals and oxidants in cigarette smoke create a pro-oxidative environment in the bloodstream that chemically modifies LDL particles. This oxidized LDL is far more likely to lodge in artery walls, trigger inflammation, and contribute to plaque buildup. Quitting reverses much of this damage over time.
Alcohol has a more complicated relationship with cholesterol. When your liver processes alcohol, it rebuilds it into triglycerides and cholesterol. Heavy drinking raises triglycerides substantially, and if levels stay elevated long enough, fat accumulates in the liver. A fatty liver loses its ability to clear cholesterol from the blood efficiently, creating a cycle where both triglycerides and LDL keep climbing.
Medical Conditions That Raise Cholesterol
Several underlying health conditions can push cholesterol higher, sometimes dramatically. These are called secondary causes of high cholesterol because the lipid problem is a downstream effect of another disease.
- Hypothyroidism: An underactive thyroid slows your metabolism, including how quickly your liver clears LDL from the blood. Treating the thyroid condition usually brings cholesterol back down.
- Type 2 diabetes: Insulin resistance drives a characteristic pattern of high triglycerides, elevated LDL, and low HDL. This is one of the reasons diabetes so sharply increases cardiovascular risk.
- Kidney disease: Nephrotic syndrome, a condition where the kidneys leak large amounts of protein into the urine, triggers the liver to overproduce cholesterol-carrying particles. Chronic kidney disease also disrupts normal lipid metabolism.
- Liver disease: Conditions that block bile flow (cholestatic liver disease) prevent cholesterol from being excreted normally, causing it to back up into the bloodstream.
- Obesity: Excess body fat, particularly around the midsection, promotes insulin resistance and increases the liver’s production of VLDL particles, which raise both triglycerides and LDL.
If your cholesterol is newly elevated and you haven’t changed your diet or habits, one of these conditions may be the cause. Treating the underlying problem often improves cholesterol without additional medication.
Medications That Raise Cholesterol
Certain medications can shift your lipid levels as a side effect. If your cholesterol climbed after starting a new prescription, it’s worth knowing which drug classes are commonly involved.
Corticosteroids like prednisone, used to control inflammation, can raise LDL and lower HDL in as little as a few weeks, especially at higher doses. Diuretics prescribed for blood pressure, particularly thiazide and loop types, tend to bump up total cholesterol and LDL temporarily. Beta-blockers, another common blood pressure medication, primarily lower HDL rather than raise LDL, but the net effect on your lipid profile is still unfavorable.
Immunosuppressants like cyclosporine, used after organ transplants or for autoimmune conditions, reliably increase LDL. Anabolic steroids cause some of the most dramatic changes, sharply raising LDL while dropping HDL. Even amiodarone, a heart rhythm medication, can push LDL higher.
Hormonal Changes and Aging
Cholesterol levels naturally shift with age, and hormonal transitions can accelerate those changes. The clearest example is menopause. As estrogen levels fall, LDL cholesterol rises. Estrogen normally helps the liver maintain its LDL receptors, so its decline reduces the body’s ability to clear LDL from the blood. Many women who had healthy cholesterol levels throughout their 30s and 40s see a noticeable jump during their late 40s and 50s.
For both men and women, LDL tends to creep upward with age even without obvious dietary or lifestyle changes. This gradual rise reflects a slow decline in how efficiently the liver processes cholesterol over decades. It’s one reason routine cholesterol screening becomes more important after age 40, even if your numbers were previously fine.