Lipoprotein(a) Unit Converter
Lipoprotein(a) Unit Converter
Convert an Lp(a) in nmol/L to an approximate mg/dL — and see how far the answer moves across the range of conversion factors in use, because no exact conversion exists.
Lp(a) nmol/L → mg/dL
nmol/L → approximate mg/dLLp(a) 125 nmol/L, assuming 2.15 nmol/L per mg/dL
An approximation, not a conversion
with the factor commonly taken as somewhere between 2.0 and 2.5
- factor
- the assumed number of nmol/L per mg/dL; it is not a physical constant, and its correct value differs from patient to patient
- kringle IV type 2
- the repeated domain in apolipoprotein(a) whose copy number varies between people, so particle mass varies and mass and particle number are not proportional
- nmol/L
- the particle-number unit, which is not affected by isoform size and is the unit consensus statements recommend for reporting
Worked example
Lp(a) 125 nmol/L, assuming 2.15 nmol/L per mg/dL
125 ÷ 2.15 = 58.1 mg/dL
At a factor of 2.0 the same result converts to 62.5 mg/dL
At a factor of 2.5 it converts to 50.0 mg/dL
A spread of 12.5 mg/dL from the same measurement — which is the point of this page
The same nmol/L result across three factors in common use
| Lp(a) (nmol/L) | ÷ 2.0 (mg/dL) | ÷ 2.15 (mg/dL) | ÷ 2.5 (mg/dL) |
|---|---|---|---|
| 75 | 37.5 | 34.9 | 30.0 |
| 100 | 50.0 | 46.5 | 40.0 |
| 125 | 62.5 | 58.1 | 50.0 |
| 150 | 75.0 | 69.8 | 60.0 |
| 250 | 125.0 | 116.3 | 100.0 |
Conventional thresholds, approximately paired
| Description | mg/dL | Approximate nmol/L |
|---|---|---|
| Low risk | < 30 | < 75 |
| Intermediate | 30 – 50 | 75 – 125 |
| Raised | > 50 | > 125 |
Why no exact conversion exists, and what to do instead
There is no exact conversion between mg/dL and nmol/L for lipoprotein(a), and this page exists to make the size of that uncertainty visible rather than to hide it behind a single number. The reason is structural. Lp(a) is an LDL-like particle with an apolipoprotein(a) tail attached, and apolipoprotein(a) contains a variable number of kringle IV type 2 repeats — anywhere from a handful to more than forty, inherited and differing between people. Particles therefore differ in mass, so a mass concentration in mg/dL and a particle concentration in nmol/L are not related by a fixed factor. The error introduced by converting depends on the patient’s own isoform size, and it is largest in exactly the people whose isoforms are unusual.
For that reason, major guidelines and consensus statements recommend that Lp(a) be measured with an isoform-insensitive assay and reported in nmol/L, and they advise against converting between the two units. If a report gives nmol/L, use nmol/L. This calculator is intended for reading an older result, or a paper that quotes the other unit, and its output should be treated as an approximation with a stated assumption attached rather than as a converted measurement.
The commonly cited thresholds are 30 mg/dL and 50 mg/dL, conventionally paired with roughly 75 and 125 nmol/L. Both of those pairings imply a factor of 2.5, while much laboratory material uses 2.0 or about 2.15, and the spread matters: a measurement of 125 nmol/L converts to anywhere between 50 and 62.5 mg/dL depending only on which factor is chosen. That is enough to move a patient across a threshold without anything about the patient changing.
The clinical handling is more settled than the units. Lp(a) is largely genetically determined and stable through adult life, so a single measurement is usually sufficient and repeat testing adds little unless an intercurrent illness or pregnancy makes the first result unreliable. A raised Lp(a) is an independent risk factor for atherosclerotic disease and for calcific aortic valve stenosis, and it warrants closer attention to every modifiable risk factor. Statins do not lower it and may raise it slightly, which is not a reason to withhold them.
Frequently asked questions
How do I convert Lp(a) from nmol/L to mg/dL?
Only approximately. Divide the nmol/L value by a factor conventionally taken as somewhere between 2.0 and 2.5. There is no exact conversion, because Lp(a) particle mass varies between people.
Why is there no exact conversion factor?
Because apolipoprotein(a) contains a variable number of kringle IV type 2 repeats, so Lp(a) particles differ in mass from person to person. Mass concentration and particle number are therefore not related by a fixed factor, and the conversion error depends on the individual’s isoform.
Which unit should Lp(a) be reported in?
In nmol/L, using an isoform-insensitive assay. Major consensus statements recommend this and advise against converting between units, because particle number is not distorted by isoform size.
What Lp(a) level counts as raised?
The figures in common use are 30 mg/dL and 50 mg/dL, conventionally paired with roughly 75 and 125 nmol/L. Values above 50 mg/dL, or above 125 nmol/L, are usually described as raised and as an independent cardiovascular risk factor.
Do I need to repeat an Lp(a) test?
Usually not. Lp(a) is largely genetically determined and stable through life, so one measurement is generally sufficient. Statins do not lower it, and may raise it slightly.
Related calculators
References
- Kronenberg F, Mora S, Stroes ESG, et al. Lipoprotein(a) in atherosclerotic cardiovascular disease and aortic stenosis: a European Atherosclerosis Society consensus statement. Eur Heart J. 2022;43(39):3925–3946.
- Nordestgaard BG, Chapman MJ, Ray K, et al. Lipoprotein(a) as a cardiovascular risk factor: current status. Eur Heart J. 2010;31(23):2844–2853.
- Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC multisociety guideline on the management of blood cholesterol. Circulation. 2019;139(25):e1082–e1143.