High cholesterol results from a combination of factors, some within your control and some not. Your liver produces most of the cholesterol in your body, and when something disrupts the balance between production and removal, levels climb. The main drivers fall into a few categories: genetics, diet, physical activity, hormonal changes, other health conditions, and certain medications.
Genetics and Family History
Some people inherit genes that make it much harder for their body to clear LDL (“bad”) cholesterol from the bloodstream. The most well-known form, familial hypercholesterolemia, is caused by a variant on chromosome 19 that affects the liver’s LDL receptors. These receptors normally grab LDL particles from your blood and pull them into the liver for processing. When they don’t work properly, LDL accumulates, sometimes pushing levels to 190 mg/dL or higher even without any dietary or lifestyle triggers.
Familial hypercholesterolemia affects roughly 1 in 250 people, and many don’t know they have it until a routine blood test reveals unusually high numbers. If one or both of your parents had high cholesterol at a young age, especially before 55 in men or 65 in women, there’s a meaningful chance a genetic component is at play. In these cases, lifestyle changes alone often aren’t enough to bring LDL into a healthy range.
Saturated Fat, Trans Fat, and Dietary Cholesterol
What you eat affects your cholesterol, but not always in the ways people assume. The biggest dietary culprits are saturated fat and trans fat, not cholesterol from food itself. Saturated fat (found in red meat, butter, cheese, and full-fat dairy) nudges your liver to produce more LDL. Trans fats, found in some processed and fried foods, are a double hit: they raise LDL while simultaneously lowering HDL (“good”) cholesterol, the type that helps shuttle excess cholesterol back to the liver for disposal.
Replacing saturated fats with unsaturated fats from sources like olive oil, nuts, and fatty fish can measurably improve your cholesterol balance. This swap is one of the most effective dietary changes you can make.
Dietary cholesterol, the kind found in egg yolks and shellfish, has a smaller effect than once thought. One large egg contains about 186 mg of cholesterol, but it doesn’t seem to raise blood cholesterol the way saturated and trans fats do. Most healthy people can eat up to seven eggs a week without increasing their risk of heart disease. That said, current guidance still suggests keeping dietary cholesterol under 300 mg per day, particularly if your levels are already elevated.
Physical Inactivity
A sedentary lifestyle shifts your cholesterol profile in the wrong direction. Regular physical activity increases the density of mitochondria in your muscles, which makes your body more efficient at burning triglycerides and processing VLDL, a precursor to LDL. Exercise also boosts production of large HDL particles, the most effective form for removing cholesterol from artery walls.
Research published in the American Heart Association’s journals found that physical activity was inversely associated with VLDL concentrations and positively associated with larger HDL particles. In practical terms, the less you move, the more your “bad” cholesterol tends to rise and your “good” cholesterol tends to fall. You don’t need intense workouts to see a benefit. Consistent moderate activity, like brisk walking most days, makes a noticeable difference over weeks and months.
Smoking
Smoking doesn’t just damage your lungs. It directly impairs the function of your HDL cholesterol. Tobacco smoke contains a reactive chemical called acrolein that modifies HDL particles and makes them dysfunctional. Research from the American Heart Association found that HDL exposed to acrolein was 30% less effective at removing cholesterol from cells and 10 to 25% less efficient at delivering cholesterol to the liver for disposal. In effect, smoking doesn’t just lower the amount of HDL in your blood; it cripples the HDL you do have.
Hormonal Changes and Aging
Cholesterol levels naturally shift with age, and the change is especially pronounced in women around menopause. Before menopause, women typically have lower LDL and higher HDL than men of the same age. Estrogen helps the liver process cholesterol efficiently. After menopause, when estrogen levels drop, LDL rises and often exceeds levels seen in men of the same age. The LDL particles also shift to a smaller, denser form that’s more likely to contribute to plaque buildup in arteries. HDL declines at the same time.
This hormonal shift explains why many women see a sudden jump in cholesterol in their late 40s or 50s, even if their diet and activity level haven’t changed. Men also experience gradual increases in LDL with age, though the rise tends to be more steady rather than tied to a single hormonal event.
Thyroid Problems and Other Health Conditions
Several underlying medical conditions can raise cholesterol independent of what you eat or how much you exercise. Hypothyroidism (an underactive thyroid) is one of the most common secondary causes. Thyroid hormones help your liver process blood and clear cholesterol. When those hormones run low, the liver works more slowly and cholesterol accumulates. As many as 13% of people with hypothyroidism also have elevated LDL. Even mildly low thyroid function, levels that fall in a borderline range, can cause a noticeable spike in cholesterol.
Type 2 diabetes and chronic kidney disease also contribute to abnormal cholesterol profiles. Diabetes tends to raise triglycerides and lower HDL, while kidney disease impairs the body’s ability to metabolize fats properly. In all of these cases, treating the underlying condition often improves cholesterol numbers without additional cholesterol-specific treatment.
Medications That Raise Cholesterol
Certain prescription drugs raise cholesterol as a side effect, which can be surprising if you’re taking them for an unrelated condition. The most notable include:
- Corticosteroids (like prednisone), used for inflammation, can quickly and significantly raise LDL while lowering HDL.
- Beta-blockers (like metoprolol and atenolol), prescribed for high blood pressure, can lower HDL.
- Diuretics (“water pills”), also used for blood pressure, cause temporary increases in total cholesterol and LDL. Thiazide diuretics tend to leave HDL unchanged, while loop diuretics may lower it slightly.
- Immunosuppressants (like cyclosporine), used after organ transplants and for autoimmune conditions, can increase LDL.
- Anabolic steroids, including testosterone, can cause dramatic LDL increases and HDL decreases.
If your cholesterol spiked after starting a new medication, that connection is worth raising with your prescriber. In many cases, alternative drugs exist that don’t carry the same lipid effects.
What Counts as High
Current guidelines from the American College of Cardiology and the American Heart Association define severe hypercholesterolemia as an LDL level of 190 mg/dL or above. For most adults with moderate heart disease risk, the treatment goal is to bring LDL below 100 mg/dL. For those at higher risk, including people who already have heart disease, the target drops to below 70 mg/dL or even below 55 mg/dL.
These numbers aren’t one-size-fits-all. Your target depends on your overall cardiovascular risk, which factors in age, blood pressure, smoking status, diabetes, and family history alongside your cholesterol numbers. A single high reading doesn’t necessarily mean you need medication, but it does mean identifying which of the causes above are driving the number up and addressing the ones you can change.