Nearly one-third of American adults have high levels of harmful low-density lipoprotein (LDL) cholesterol circulating through their blood, which doubles their risk of heart disease compared to people with normal levels (see “Classifying LDL level”). Most of these people likely have dozens of different genetic mutations, each of which raises LDL by a little bit. Over time — coupled with a less-than-ideal diet and not enough exercise — their LDL levels slowly creep up.

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But what about very high LDL? “About 5% of the population have LDL values of 190 or higher, and their risk of heart disease is five times higher than people with near-optimal LDL,” says Dr. Amit V. Khera, a cardiologist at Harvard-affiliated Brigham and Women’s Hospital. Within this group, an important minority has familial hypercholesterolemia (FH), a genetic condition that affects about one in 250 adults.

What is FH?

Most people with FH have a mutation or variant in one of three different genes that provide instructions that help remove excess LDL from the bloodstream. People who inherit one variant from a parent have heterozygous FH, which can cause LDL levels as high as 350 milligrams per deciliter (mg/dL). People who inherit two variants (one from each parent) have homozygous FH. This very rare condition, which affects only about four in a million people, can lead to LDL levels as high as 1,000 mg/dL.

Excess LDL in the bloodstream can accumulate in the skin and tendons, which is why some people with FH develop small, cholesterol-filled nodules on their eyelids or their tendons, especially those along the backs of the hands, the elbows, or the backs of the ankles (the Achilles tendons). But the biggest threat is the buildup of LDL in the arteries supplying the heart. People with untreated FH can succumb to a heart attack in their 40s or earlier, likely because of the cumulative exposure to high LDL starting at birth.

Classifying LDL level

These targets are for people without known heart disease. People who have heart disease or are at high risk for it should aim for an LDL of 70 or lower.

LDL category

Value (mg/dL)

Optimal

100

Near/above optimal

100-129

Borderline high

130-159

High

160-189

Very high

190 or higher

Is genetic testing necessary?

If a person’s close relative — a parent or sibling — has very high cholesterol or had a heart attack at a young age (before 55 in a man or 65 in a woman), that’s a red flag for possible FH. Genetic testing isn’t strictly necessary, as high LDL is a reliable sign of heart disease risk in anyone, regardless of the cause.

However, FH testing can be beneficial for two reasons, says Dr. Khera. “First, if you’ve struggled your whole life with high cholesterol despite following a healthy diet and getting regular exercise, knowing there’s a genetic explanation is often helpful.” Second, an FH diagnosis can be important for your biological parents, siblings, and children, each of whom has a 50/50 chance of having the same FH variant.

Although guidelines recommend checking cholesterol levels in children and adolescents at least once between ages 9 and 11 and again between ages 17 and 21, such tests usually aren’t done. And when high cholesterol is found, physicians typically don’t treat children and teens very aggressively. But once they hit adulthood, treating very high cholesterol is crucial, says Dr. Khera. The Family Heart Foundation has more information on FH, including a tool to search for doctors who specialize in the condition.

Treating very high LDL

The latest cholesterol treatment guidelines emphasize the importance of lowering excessively high LDL and keeping it low for decades. “It’s most practical to focus on finding and treating severe hypercholesterolemia, regardless of the underlying cause,” says Dr. Khera. The first choice is a high-intensity statin: 40 to 80 milligrams (mg) of atorvastatin (Lipitor) or 20 to 40 mg of rosuvastatin (Crestor), both of which will slash LDL by about 50%. While those drugs get many people with very high LDL close to the target range of 70 mg/dL for high-risk individuals, some need additional medications, which may include

• ezetimibe (Zetia), a pill that inhibits cholesterol absorption in the gut
• bempedoic acid (Nexletol), a pill that blocks cholesterol production in the liver
• alirocumab (Praluent) or evolocumab (Repatha), injectable drugs that help remove excess LDL from the bloodstream
• inclisiran (Leqvio), a twice-yearly injection that interferes with a protein in the liver that regulates LDL.

Following heart-healthy habits, as outlined in the American Heart Association’s Life’s Essential 8 is also crucial.

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