Lipoprotein(a) or Lp(a): What It Is and What Your Levels Mean

One of the biggest heart disease risk factors is something you probably haven’t heard of, let alone had tested: lipoprotein(a), also written as Lp(a).

Lp(a) is a cholesterol-carrying particle in your blood that raises your risk of heart attack, stroke, and a narrowing of a heart valve, and about one in five people worldwide has a high level of it. Yet it isn't part of a standard cholesterol test, so unless a doctor has specifically ordered it, you likely don't know your number.

Below, we'll explain what Lp(a) actually is, why it's different from LDL and the other cholesterol numbers you may already know, and what a high result means for you and your family.

What Is Lipoprotein(a)?

Picture your bloodstream as a delivery network. Cholesterol doesn't dissolve in blood on its own, so your body packages it inside small round carriers called lipoproteins, which you can picture as delivery vehicles carrying cholesterol cargo to different parts of your body. One of the most familiar of these vehicles is LDL cholesterol, often called "bad" cholesterol, which can drop its cargo off inside artery walls and contribute to plaque buildup over time.

Lp(a) is best understood as a type of that same LDL vehicle. It's built the same way as LDL, but with one extra part welded onto the outside: a protein called apolipoprotein(a), or apo(a) for short.

Think of apo(a) as an extra hook bolted onto the side of the vehicle. That hook does two things. First, it makes the particle more likely to snag inside artery walls and contribute to plaque, the same way LDL does. Second, it interferes with your body's natural system for breaking down blood clots, making clots more likely to form and harder to clear.

This is why a high Lp(a) level raises risk for heart attack and stroke, and it's also linked to a narrowing of the heart's aortic valve called aortic stenosis, a separate condition from plaque buildup in the arteries.

Is Lp(a) Genetic?

Yes, almost entirely.

Unlike LDL cholesterol or triglycerides, which respond to diet, exercise, and weight, your Lp(a) level is set by the genes you inherited from your parents, and healthy eating and exercise habits won't change it. Because of this, your Lp(a) level is usually stable for your entire adult life. One blood test typically tells you what you need to know, unlike LDL or triglycerides, which doctors recheck periodically over the years.

This genetic link also means a high result isn't just about you. If your Lp(a) comes back high, it's worth sharing with close family members, like your parents, siblings, and children, since they have a real chance of carrying the same genetic tendency.

This is sometimes called cascade testing: checking close relatives of someone with a significant genetic finding. Lp(a) is a good example of how family history goes beyond cholesterol numbers: you can have a completely normal cholesterol panel and still have inherited high Lp(a).

Why Isn't Lp(a) Part of a Standard Cholesterol Test?

Lp(a) requires its own separate blood test order. It has never been included in the standard cholesterol panel your doctor typically requests at a checkup, partly because, until recently, there wasn't much a doctor could specifically do about a high result beyond managing other risk factors. That's beginning to shift.

The most recent major cholesterol guideline in the United States now recommends that every adult have their Lp(a) level measured at least once, specifically to identify people who carry this extra, otherwise invisible layer of risk.

Despite that, fewer than five percent of Americans have actually been screened, so it's worth directly asking your doctor to order it rather than assuming it's already been checked.

Who Should Get Tested for Lp(a)?

Since testing isn't automatic, it helps to know when to specifically ask for it. A few situations make Lp(a) testing especially worth requesting:

• You have a personal or family history of heart attack or stroke at a younger age than expected, particularly before 55 in men or 65 in women.
• A close family member has been diagnosed with high Lp(a) or a genetic cholesterol condition called familial hypercholesterolemia.
• Your LDL and other standard cholesterol numbers look normal, but you still have unexplained heart disease or a strong family history of it.
• You've had unexplained aortic stenosis, especially at a younger age.

If any of these apply to you, it's worth raising Lp(a) specifically with your doctor at your next visit, since it won't be added automatically to a routine cholesterol panel.

What Is a Normal Lp(a) Level?

Lp(a) is reported in one of two units, nmol/L or mg/dL, depending on the lab, which is a common source of confusion worth flagging upfront. The two aren't interchangeable using simple math, but the categories below reflect how the two units roughly line up in practice, according to the American Heart Association:

At the very high level, your risk may roughly double compared to a normal result. If your lab report shows a different unit than the one you expected, that's normal, not an error, but it's worth asking your doctor to confirm which category your specific number falls into.

Why Does High Lp(a) Matter for Your Heart?

High Lp(a) raises risk in three distinct ways, and it's worth understanding them as separate problems rather than one blurred risk.

• It contributes to plaque buildup in your arteries. Like LDL, the Lp(a) particle can lodge inside artery walls and add to the plaque that narrows arteries over time, raising your risk of heart attack.
• It interferes with your body's ability to clear blood clots. The extra apo(a) hook on the particle disrupts a normal clot-clearing process, making it easier for clots to form and harder for your body to break them down, which raises stroke risk specifically.
• It's linked to aortic stenosis. High Lp(a) significantly increases the risk of aortic stenosis, a narrowing of the aortic valve that can eventually require valve replacement. This affects a valve in the heart itself rather than the blood vessels feeding it.

What Can You Do About High Lp(a)?

Right now, there's no medication specifically approved to lower Lp(a). However, it's an active area of research, with newer treatments currently being tested in clinical trials.

It's worth knowing what doesn't work here too:

• Statins, the most common cholesterol medication, are highly effective at lowering LDL, but they don't significantly lower Lp(a), and some research suggests they may even raise it slightly.
• PCSK9 inhibitors, a newer group of medicines originally developed to lower LDL, does reduce Lp(a) by roughly 20 percent on average. But it isn't strong enough to be considered a Lp(a) treatment on its own.

Since Lp(a) itself is hard to change, doctors instead focus on being more aggressive about every other risk factor you can control. That means:

• Tighter management of LDL cholesterol
• Managing blood pressure and blood sugar
• Quitting smoking if you smoke
• Exercising regularly
• Eating a heart-healthy diet

The overall goal is to reduce the total load on your arteries, since your heart risk is a combination of Lp(a) plus everything else going on in your blood vessels, not Lp(a) in isolation.

A blood test tells you your Lp(a) number, but it can't tell you whether plaque has actually started building up in your arteries yet. That's the question a heart scan answers. A calcium score test is fast and affordable and shows hard plaque. A CCTA is expensive and more thorough, picking up soft plaque and showing where arteries have narrowed. That matters for Lp(a) in particular: in a Mount Sinai study of 547 people without symptoms, Lp(a) was the only blood marker in the study independently linked to risky soft plaque, the kind a calcium score misses. Knowing what's in your arteries helps you and your doctor personalize how aggressively to manage everything else, and spotting plaque early gives you a head start.

The Bottom Line on Lp(a)

Lp(a) is a cholesterol-carrying particle similar to LDL, but with an added feature that raises your risk of heart attack, stroke, and aortic stenosis. However, it’s not usually a part of routine testing, which means most people have simply never had it checked.

If you haven't had your Lp(a) measured, it's worth asking your doctor to order it, especially if heart disease runs in your family. A high result doesn't have a specific medication yet, but it does change how aggressively your other risk factors should be managed.