High cholesterol comes from a mix of what you eat, how active you are, your genetics, and sometimes medical conditions or medications you’re already taking. For most adults, a total cholesterol level below 200 mg/dL is considered healthy, with LDL (“bad”) cholesterol ideally under 100 mg/dL. When those numbers creep up, it’s rarely one single cause. Several factors usually work together.
Saturated and Trans Fats
Diet is the factor most people can control, and saturated fat is the biggest dietary driver of high LDL cholesterol. When you eat a lot of saturated fat (found in red meat, butter, cheese, and full-fat dairy), your liver responds by pulling fewer LDL particles out of your bloodstream. Normally, your liver has receptors that grab LDL cholesterol and clear it from circulation. Saturated fat reduces the number of those receptors, so more LDL stays floating in your blood. Research published in the Journal of Lipid Research confirmed this mechanism in humans: when people reduced their saturated fat intake, the number of LDL receptors on their cells increased, and their LDL levels dropped.
Trans fats are even worse. They raise LDL while simultaneously lowering HDL (“good”) cholesterol. Trans fats are found in partially hydrogenated oils, which still show up in some fried foods, packaged baked goods, and margarine. Although many countries have restricted trans fats in the food supply, they haven’t disappeared entirely.
Genetics and Family History
Some people do everything right and still have high cholesterol. The most common inherited form is familial hypercholesterolemia, which affects roughly 1 in 200 to 1 in 250 people worldwide. It’s the most common inherited condition affecting the heart and blood vessels, yet many people who have it don’t know.
The condition is usually caused by a mutation in the LDLR gene, which provides instructions for building those same LDL receptors on the liver. When the gene is faulty, the liver can’t clear LDL efficiently, so levels stay dangerously high from a young age. Less commonly, mutations in genes called APOB, PCSK9, or LDLRAP1 cause the same problem through slightly different pathways. If one of your parents has this condition, you have a 50% chance of inheriting it. People with familial hypercholesterolemia can have LDL levels two to three times higher than normal, even as children or young adults.
Physical Inactivity
Sitting for long periods does more than weaken your muscles. When your muscles aren’t contracting regularly, an enzyme called lipoprotein lipase becomes less active. This enzyme breaks down fats in your blood and helps produce HDL cholesterol. Without it working efficiently, triglyceride levels rise and HDL levels fall.
Bed rest studies show the extreme version of this effect: prolonged immobility leads to measurably higher triglycerides, lower HDL, and reduced insulin sensitivity. You don’t need to be bedridden for this to matter, though. Even interrupting long stretches of sitting with brief movement appears to improve how your body processes fats after a meal. The key takeaway is that regular physical activity directly supports your body’s ability to manage cholesterol, and a sedentary routine undermines it.
Age and Hormonal Changes
Cholesterol levels naturally rise with age for both men and women, but the shift is especially dramatic for women after menopause. Before menopause, estrogen helps keep LDL levels lower and HDL levels higher. Once estrogen declines, LDL cholesterol rises and often exceeds the levels seen in men of the same age. The LDL particles also tend to become smaller and denser, a form that’s more likely to contribute to artery damage. HDL levels drop at the same time, removing a layer of protection.
This is why many women who had perfectly normal cholesterol in their 30s and 40s see their numbers jump in their 50s without any obvious change in diet or habits.
Smoking
Cigarette smoke lowers HDL cholesterol through a specific chemical mechanism. Components in the gas phase of smoke disable an enzyme that’s essential for HDL to mature and function properly. This enzyme normally helps HDL pick up cholesterol from your tissues and carry it back to the liver for disposal. When smoke inactivates it, HDL can’t do its job, and your “good” cholesterol levels drop. Smoking also promotes oxidation of LDL particles, making them more harmful to artery walls. The effect is dose-dependent: the more you smoke, the worse the impact on your lipid profile.
Body Weight
Carrying excess weight, particularly around the midsection, tends to raise triglycerides and LDL while lowering HDL. Fat tissue is metabolically active and influences how your liver produces and processes cholesterol. Even modest weight loss (5 to 10% of body weight) can improve cholesterol numbers noticeably. The relationship works in both directions: the same dietary patterns that cause weight gain, like excess sugar, refined carbohydrates, and saturated fat, also directly raise cholesterol.
Chronic Stress
Stress doesn’t just feel bad. It triggers a hormonal chain reaction that physically involves cholesterol. When you’re under chronic stress, your adrenal glands ramp up cortisol production. Cortisol is literally built from cholesterol: your adrenal glands pull HDL cholesterol from the blood and convert it into the stress hormone. Over time, this increased demand can shift your lipid balance. Chronic stress also tends to drive behaviors that worsen cholesterol, like overeating, choosing comfort foods high in saturated fat, sleeping poorly, and skipping exercise.
Medical Conditions That Raise Cholesterol
Several health conditions cause what’s called secondary hypercholesterolemia, meaning the high cholesterol is a side effect of another disease rather than a primary problem.
- Hypothyroidism is one of the most common culprits. Your thyroid hormones help regulate how quickly your liver clears LDL from the blood. When thyroid function is low, LDL clearance slows down and levels rise. Treating the thyroid condition often brings cholesterol back to normal.
- Kidney disease, especially nephrotic syndrome and kidney failure, disrupts how your body handles fats and can cause significant increases in total cholesterol and triglycerides.
- Diabetes frequently comes with a pattern of high triglycerides and low HDL, sometimes called diabetic dyslipidemia. Poorly controlled blood sugar makes this worse.
- Liver disease, particularly conditions that block bile flow, can raise cholesterol because bile is one of the main ways your body eliminates excess cholesterol.
If your cholesterol is high and doesn’t respond well to lifestyle changes, one of these underlying conditions may be contributing. A basic thyroid panel and kidney function test can help rule them out.
Medications That Raise Cholesterol
Some commonly prescribed drugs can push your cholesterol in the wrong direction, and many people don’t realize this is happening.
- Corticosteroids like prednisone, used for inflammation and autoimmune conditions, can quickly and significantly raise LDL while lowering HDL.
- Beta-blockers prescribed for high blood pressure (including propranolol, atenolol, and metoprolol) tend to lower HDL cholesterol.
- Thiazide diuretics, another common blood pressure medication class, cause temporary increases in total cholesterol and LDL.
- Immunosuppressants like cyclosporine, used after organ transplants, raise LDL levels as a known side effect.
- Anabolic steroids cause dramatic increases in LDL and decreases in HDL.
If you’ve started a new medication and noticed your cholesterol numbers shift, the drug may be a factor. This doesn’t necessarily mean you should stop taking it, but it’s worth discussing with your prescriber so they can weigh the tradeoffs.
What Healthy Levels Look Like
For adults 20 and older, these are the generally recommended targets:
- Total cholesterol: below 200 mg/dL
- LDL cholesterol: below 100 mg/dL
- HDL cholesterol: 60 mg/dL or higher is ideal. Below 40 mg/dL for men or below 50 mg/dL for women is considered low.
- Triglycerides: below 150 mg/dL
For children and teens (19 and younger), the thresholds are slightly different: total cholesterol should be below 170 mg/dL and LDL below 110 mg/dL. Cholesterol testing is recommended starting at age 9 to 11 for most children, and earlier if there’s a strong family history of heart disease or high cholesterol.