LDL cholesterol rises when your liver either produces too much of it or can’t pull enough of it back out of your bloodstream. Most cases trace back to a combination of diet, genetics, lifestyle habits, and sometimes an underlying medical condition or medication. Understanding what drives your specific number up is the first step toward bringing it down.
How Your Liver Controls LDL Levels
Your liver is the command center for LDL cholesterol. It packages fats into particles called VLDL and releases them into your blood. As these particles travel through your body, enzymes strip away their fat cargo, gradually converting them into smaller, denser LDL particles.
The key to keeping LDL in check is what happens next. Your liver has special receptors on its surface that grab LDL particles out of the bloodstream and recycle them. When these receptors are plentiful, your liver clears LDL efficiently and blood levels stay low. When receptor numbers drop, LDL accumulates in your blood with nowhere to go. This receptor system is the single most important factor determining your LDL level, and nearly everything that raises LDL, from diet to genetics to medications, works by disrupting it.
Saturated Fat and Trans Fat
Saturated fat is the most well-established dietary driver of high LDL. When you eat more of it, the fat directly suppresses LDL receptor activity on your liver cells. With fewer receptors pulling LDL out of circulation, levels climb. Polyunsaturated fats have the opposite effect: they increase receptor activity, helping your liver clear more LDL from the blood. This is why swapping butter, fatty cuts of meat, and full-fat dairy for sources of unsaturated fat (olive oil, nuts, fatty fish) consistently lowers LDL in clinical studies.
Industrial trans fats, found in partially hydrogenated oils, are a double hit. They raise LDL while simultaneously lowering HDL, your protective cholesterol. For every 1% of daily calories from industrial trans fats replacing healthier fats, LDL rises and the ratio of LDL to HDL worsens measurably. Most countries have now banned or severely restricted artificial trans fats in food, but they still show up in some processed products, particularly imported or small-batch goods.
Genetics and Familial Hypercholesterolemia
Some people do everything right with diet and exercise and still have high LDL. The most common genetic explanation is familial hypercholesterolemia (FH), an inherited condition that affects roughly 1 in 300 people. That makes it far more common than many doctors realize, and the majority of people who have it don’t know.
FH is caused by mutations in genes that control the LDL receptor system. The most frequent culprit is the LDLR gene itself, which codes for the receptor that pulls LDL out of your blood. When this gene is faulty, your liver can’t clear LDL normally, and levels run high from childhood onward. Other genes involved include APOB (which affects how LDL particles attach to receptors) and PCSK9 (which controls how quickly receptors are broken down). People with FH from one parent typically have LDL levels above 190 mg/dL. Those who inherit mutations from both parents can have LDL above 400 mg/dL and face heart disease risk in their teens or twenties.
Beyond FH, common genetic variations across dozens of genes can nudge LDL levels higher or lower by modest amounts. These don’t cause dramatic spikes on their own, but they help explain why two people eating the same diet can have very different cholesterol numbers.
Body Weight and Physical Activity
Carrying excess weight, particularly around the midsection, tends to raise LDL while lowering HDL. Excess body fat increases the liver’s production of VLDL particles, which eventually become LDL. It also promotes insulin resistance, which further disrupts the cholesterol-clearing machinery.
Regular exercise reshapes your LDL profile in ways that go beyond total numbers. Physical activity increases the activity of an enzyme called lipoprotein lipase by as much as 39% after several months of consistent training, based on a large study of over 600 participants. This enzyme breaks down fat-rich particles more efficiently, which shifts LDL particles toward larger, less harmful forms and reduces the concentration of small, dense LDL, the type most strongly linked to artery damage. Exercise also decreases the activity of a second enzyme that makes LDL particles smaller and denser. Even when your total LDL number doesn’t drop dramatically with exercise, the composition of your LDL particles can improve significantly.
Medical Conditions That Raise LDL
Several health conditions can push LDL higher as a secondary effect. Hypothyroidism (underactive thyroid) is one of the most common. Thyroid hormones directly regulate how your liver processes cholesterol, including the production, clearance, and transformation of LDL. When thyroid hormone levels fall, the liver’s ability to remove LDL from the bloodstream slows down. This is why a thyroid panel is often one of the first tests ordered when LDL is unexpectedly high. Treating the thyroid problem usually brings cholesterol back down.
Other conditions associated with elevated LDL include kidney disease (particularly nephrotic syndrome, where protein loss in urine triggers the liver to ramp up cholesterol production), type 2 diabetes, and liver diseases that impair bile acid production. Pregnancy also temporarily raises LDL, sometimes substantially, though levels typically normalize after delivery.
Medications That Increase LDL
A number of commonly prescribed medications can raise LDL as a side effect. If your cholesterol climbed after starting a new drug, it’s worth considering whether the medication is a factor.
- Thiazide diuretics (used for blood pressure): High doses can increase LDL by roughly 10%.
- Corticosteroids (used for inflammation and autoimmune conditions): High doses tend to raise LDL, triglycerides, and HDL together.
- Anabolic steroids: Can increase LDL by 10 to 40% while cutting HDL by up to half.
- Certain diabetes medications: SGLT2 inhibitors raise LDL by a small but measurable amount (about 3 mg/dL on average), and rosiglitazone also increases LDL.
- Immunosuppressants: Drugs used after organ transplants or for autoimmune diseases, including cyclosporine and mTOR inhibitors, can raise LDL by interfering with receptor function and the breakdown of cholesterol-carrying proteins.
- Some antiviral drugs: Direct-acting antivirals used to treat hepatitis C have been linked to LDL increases of up to 27%.
These effects vary by dose and individual. In many cases, the benefit of the medication outweighs the cholesterol impact, but your doctor may adjust the treatment plan or add cholesterol-lowering therapy to compensate.
What Your LDL Number Means
Current guidelines from the American College of Cardiology and American Heart Association don’t use a single “normal” cutoff for adults. Instead, your target depends on your overall risk of heart disease over the next 10 years, calculated from factors like age, blood pressure, smoking status, and diabetes.
For adults at low cardiovascular risk (under 3% chance of a heart event in the next decade), LDL below 160 mg/dL is generally considered acceptable, and the focus is on healthy habits rather than medication. At intermediate risk (5 to 10%), the goal drops to below 100 mg/dL. For those at high risk (10% or greater), guidelines target below 70 mg/dL. People who already have heart disease aim for below 55 mg/dL in the highest-risk cases. Any LDL at or above 190 mg/dL is classified as severe hypercholesterolemia regardless of other risk factors, and it warrants further evaluation for genetic causes like familial hypercholesterolemia.
For children and adolescents, the thresholds are simpler: below 110 mg/dL is considered acceptable, 110 to 129 is borderline, and 130 or above is abnormal.