Lipoprotein(a), pronounced "L-P-little-a" and almost universally called Lp(a), is the cardiovascular risk factor most people have never heard of — including a lot of physicians. It is a particle similar to LDL but with an extra protein attached that makes it both more atherogenic (more likely to cause plaque) and more thrombogenic (more likely to encourage clots).
Three things make Lp(a) different from every other lipid test:
- It is almost entirely genetic. Diet, exercise, and statins barely move it.
- It is stable for life. One measurement is usually enough — your level at 30 will be very close to your level at 60.
- About 1 in 5 adults has elevated Lp(a), and most of them do not know it. Many find out only after a cardiovascular event.
The 2026 ACC/AHA guidelines now recommend that every adult get an Lp(a) measurement at least once. The European Atherosclerosis Society went further: they recommend it as routine in all primary cardiovascular risk assessments.
What Lp(a) actually is
An Lp(a) particle is essentially an LDL particle with an extra protein — apolipoprotein(a), or apo(a) — covalently attached. That apo(a) protein resembles plasminogen, the body's master clot-dissolving enzyme. Researchers think Lp(a) competes with plasminogen for binding sites, slowing clot dissolution. It also accumulates in the artery wall more readily than LDL.
How much Lp(a) you produce is determined almost entirely by the LPA gene, which has unusual variability — different alleles produce wildly different protein sizes. The smaller the apo(a) isoform, the more Lp(a) particles you make. This is why the variation across people spans roughly a 1000-fold range.
Importantly, Lp(a) is reported in two different units depending on the lab:
- nmol/L — the modern, mass-independent unit. Targets are referenced this way.
- mg/dL — older mass-based unit. Conversion is approximate (mg/dL × 2.5 ≈ nmol/L) but unreliable in individuals because particle mass varies with isoform size.
If your lab reports mg/dL, ask whether they can also provide nmol/L. The international consensus is to use nmol/L for clinical decisions.
Lp(a) cutoffs
| Demographic | Low | High | Unit |
|---|---|---|---|
| Low risk | 0 | 74 | nmol/L |
| Intermediate risk | 75 | 124 | nmol/L |
| High risk | 125 | 249 | nmol/L |
| Very high risk | 250 | 1000 | nmol/L |
| Low risk (mg/dL) | 0 | 29 | mg/dL |
| High risk (mg/dL) | 50 | 200 | mg/dL |
The 2026 ESC/EAS targets, broadly mirrored by ACC/AHA:
- Below 75 nmol/L (~30 mg/dL): low risk. About half the population.
- 75–125 nmol/L (~30–50 mg/dL): intermediate risk. Risk modifier — may push borderline patients toward more aggressive LDL lowering.
- 125–250 nmol/L (~50–100 mg/dL): high risk. Treat aggressively to LDL targets, address all other modifiable risk factors.
- Above 250 nmol/L (~100 mg/dL): very high risk. Approximately 1 in 20 adults. Risk approaches that of established cardiovascular disease.
Above 425 nmol/L (~180 mg/dL), the risk of premature cardiovascular disease is substantial — roughly equivalent to having heterozygous familial hypercholesterolemia.
What high Lp(a) means
Roughly 20% of adults have Lp(a) above 125 nmol/L. These individuals have:
- Increased lifetime risk of heart attack and ischemic stroke, independent of LDL.
- Increased risk of aortic stenosis — Lp(a) is the strongest known causal genetic risk factor for calcific aortic valve disease.
- Increased risk of peripheral artery disease.
- Earlier onset of cardiovascular events in many cases — a 45-year-old with high Lp(a) and otherwise unremarkable risk factors can present with premature coronary disease.
Family screening matters. Lp(a) is autosomal codominant — children of someone with high Lp(a) have roughly a 50% chance of inheriting elevated levels. If your Lp(a) is high, your siblings, children, and parents should be tested.
What to do about it:
- Optimize every other risk factor. Statins, blood pressure control, diabetes management, smoking cessation, weight, and exercise all matter even more when Lp(a) is high. The total cardiovascular risk is what your body experiences.
- More aggressive LDL targets. The 2026 guidelines recommend pushing LDL lower in people with elevated Lp(a) — typically below 70 mg/dL or below 55 in higher-risk patients.
- PCSK9 inhibitors lower Lp(a) by 20–30% in addition to lowering LDL. They are not approved specifically for Lp(a) but the combined benefit is meaningful.
- Aspirin is reasonable to consider in primary prevention if Lp(a) is high and bleeding risk is acceptable — recent analyses suggest more benefit in this group than in the general population.
- Lipoprotein apheresis — physical removal of Lp(a) from the blood — is reserved for patients with progressive disease and very high Lp(a) on maximum therapy.
- Targeted Lp(a)-lowering drugs (pelacarsen, olpasiran) are in late-phase trials. Phase 3 outcomes data is expected in 2026–2027. If they work, they will be the first specific Lp(a) therapy.
Low Lp(a)
Low Lp(a) is favorable. There is no known downside to having very low Lp(a), and people with naturally low levels enjoy modestly reduced cardiovascular risk all else equal. No clinical action is needed.
Why one Lp(a) test is usually enough
Lp(a) is one of the few lab values that does not need ongoing monitoring. Once you know your level, you know it for life — within roughly 10–15% variability — barring a change in kidney function, an inflammatory condition, or pregnancy.
This makes Lp(a) the ultimate "test once, act forever" measurement. Unlike LDL or triglycerides, you do not need to recheck Lp(a) annually unless you start a therapy specifically aimed at it.
Conditions that can transiently raise Lp(a):
- Acute inflammation, infection, or surgery (Lp(a) is a mild acute-phase reactant)
- Severe kidney disease (especially nephrotic syndrome)
- Hypothyroidism
- Pregnancy
- Menopause (small permanent rise)
If a baseline Lp(a) was measured during one of these states and looks unusually high, repeat after 3–6 months once the underlying issue has resolved.
Track this biomarker over time in AskAnything.health — upload your lab results and see trends at a glance.
When to act
- Lp(a) above 125 nmol/L (~50 mg/dL): review every modifiable risk factor — LDL, blood pressure, diabetes, smoking, weight. Aggressive LDL lowering is usually justified.
- Lp(a) above 250 nmol/L (~100 mg/dL): the conversation typically turns toward early statin therapy, more frequent imaging (coronary calcium scoring), and screening of first-degree relatives.
- Premature cardiovascular disease in your family (heart attack before 55 in men, 65 in women) — Lp(a) testing is particularly valuable.
- Aortic stenosis or calcific valve disease in the family — same.
This information is for educational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider about your lab results.
Tests that complete the picture
- LDL Cholesterol — the primary lever for risk reduction even when Lp(a) is high.
- Apolipoprotein B — the broader atherogenic-particle count, which includes Lp(a).
- Total cholesterol and HDL — round out the standard panel.
- hs-CRP — Lp(a) and inflammation are independent risk axes; both matter.
- Coronary artery calcium (CAC) score — imaging that quantifies plaque already present. Particularly useful when Lp(a) is elevated and you and your doctor are deciding how aggressively to treat.