hs-CRP Unit Converter
hs-CRP Unit Converter
Convert high-sensitivity CRP between mg/L, mg/dL, µg/mL and ng/mL — and see the fact that makes this a separate page from the ordinary CRP converter: hs-CRP is the same molecule, and the whole cardiovascular risk banding at 1 and 3 mg/L sits inside what a standard CRP assay reports as normal.
hs-CRP converter
mg/L ⇄ mg/dLhs-CRP 3.6 mg/L, read against the cardiovascular risk banding
Formula and conversion factors
µg/mL = mg/L (numerically identical)
ng/mL = mg/L × 1 000
nmol/L: sourced, and deliberately not offered — see below
- ÷ 10
- a decilitre is a tenth of a litre, so 3.6 mg/L is 0.36 mg/dL. This is the error that matters on a CRP report: 3 mg/dL is 30 mg/L, which is an acute-phase response, while 3 mg/L is a cardiovascular risk band
- µg/mL = mg/L
- the same concentration written two ways, with nothing to multiply. It appears on research assays and some immunology reports
- hs-CRP is not a different analyte
- it is the same pentameric protein measured by an assay with a lower working range. Roche’s high-sensitivity assay measures from 0.1 mg/L; its standard CRP assay starts at 0.6. Nothing about the molecule or the units changes
- the nmol/L that is not here
- Roche’s inserts do publish one — 5 mg/L is given as 47.6 nmol/L, a factor of 9.52 — but that implies an assumed pentamer mass of 105 kDa, where the sequence mass is nearer 115 kDa and would give 8.70. A 9% disagreement makes it a calibration, not a conversion, and molar reporting is not used clinically. Both figures are in the last table
- two samples, averaged
- the recommended protocol is two measurements about two weeks apart, both taken when the patient is clinically well, averaged before use. A single hs-CRP is a poor estimate of a baseline
Worked example
hs-CRP 3.6 mg/L, read against the cardiovascular risk banding
3.6 mg/L = 0.360 mg/dL = 3.60 µg/mL = 3,600 ng/mL
Against the cardiovascular banding: above 3 mg/L, the high relative-risk tertile
Against the standard CRP reference interval of below 5 mg/L: normal, and a standard assay's report would flag nothing
Both verdicts are correct for the same sample. That is the page in one line — and had this been 12 mg/L instead, neither would apply, because above about 10 mg/L an hs-CRP is reporting an acute-phase response and should be repeated in two weeks
The risk bands sit inside the reference interval
| mg/L | mg/dL | What kind of statement | |
|---|---|---|---|
| Low relative cardiovascular risk | < 1 | < 0.1 | A tertile of the population, AHA/CDC 2003 |
| Average relative cardiovascular risk | 1 – 3 | 0.1 – 0.3 | A tertile of the population |
| High relative cardiovascular risk | > 3 | > 0.3 | A tertile of the population |
| Consensus adult reference interval | < 5 | < 0.5 | A laboratory reference interval, standardised to ERM-DA474/IFCC |
| Not interpretable for vascular risk | > 10 | > 1.0 | An acute-phase response. Repeat after two weeks once well |
Two assays, one molecule, different working ranges
| High-sensitivity assay | Standard assay | |
|---|---|---|
| Roche assay name | Cardiac C-Reactive Protein (Latex) High Sensitive | Tina-quant C-Reactive Protein IV |
| Measuring range | 0.1 – 20 mg/L | 0.6 – 350 mg/L |
| The same range in nmol/L, as the insert prints it | 0.952 – 190 | 5.7 – 3,332 |
| Method | Particle-enhanced turbidimetric assay, latex-bound monoclonal anti-CRP | Particle-enhanced immunoturbidimetric assay, the same principle |
| Traceable to | CRM 470 lineage, via the earlier high-sensitive assay | ERM-DA474/IFCC certified reference material |
| Can it resolve the 1 mg/L risk boundary? | Yes — its range starts at 0.1 mg/L | Not reliably; its range starts at 0.6 mg/L |
| Can it quantify a bacterial infection at 200 mg/L? | No — it tops out at 20 mg/L | Yes |
The molar unit this page does not offer
| Basis | Assumed pentamer mass | nmol/L per mg/L | Status |
|---|---|---|---|
| Roche package inserts, both assays | 105 kDa, implied by their own figures | 9.52 | Published by the manufacturer, and internally consistent across four separate range statements |
| UniProt P02741: 206-residue mature subunit, discoid pentamer of five non-covalently bound subunits | About 115 kDa | 8.70 | Arithmetically derived from the sequence, and not what the inserts use |
The same molecule, a different working range, and a reference interval that hides the answer
There is no such thing as high-sensitivity C-reactive protein as a molecule. hs-CRP and CRP are one pentameric acute-phase protein, made by the liver under interleukin-6 stimulation, reported in the same units and standardised to the same certified reference material. What differs is the assay’s working range. Roche’s high-sensitivity assay measures from 0.1 to 20 mg/L; its standard CRP assay measures from 0.6 to 350. Both are particle-enhanced turbidimetric methods using latex-bound monoclonal antibodies, and both trace back to the same international reference preparation. The high-sensitivity version exists because the cardiovascular question lives between about 0.5 and 5 mg/L, where a standard assay is at or beneath its lower measuring limit; the standard version exists because a bacterial infection produces 100 to 300 mg/L, which is off the top of the high-sensitivity scale altogether. For the unit arithmetic alone, the ordinary CRP unit converter does the same job.
Once that is clear, the central oddity of the test follows from it. The AHA/CDC banding published by Pearson and colleagues in 2003 divides the population into thirds: below 1 mg/L is low relative cardiovascular risk, 1 to 3 mg/L average, above 3 mg/L high. The consensus adult reference interval a standard CRP is read against — printed on the same manufacturer’s package inserts — is below 5 mg/L. So every one of those bands lies inside what a laboratory calls normal. A patient in the high relative-risk tertile at 4 mg/L has a CRP that no standard report would flag, and a clinician reading the laboratory’s own reference interval would conclude, correctly by that standard and uselessly for the purpose, that there is nothing to see. The bands are not a narrower version of the reference interval; they are a different question asked of the same healthy population, sorting it by outcome rather than describing its spread. The hs-CRP cardiovascular risk calculator does that sorting.
Two practical rules attach to that, and neither is about units. First, a single hs-CRP is a poor estimate of anyone’s baseline, because the protein rises within hours of a stimulus most people never notice and falls with a half-life of about nineteen hours. The recommended protocol is two samples about two weeks apart, both drawn when the patient is clinically well, with the average used. Second, above about 10 mg/L the result stops being a cardiovascular measurement at all. At that level an acute-phase response is present and is far more likely to reflect infection, injury, active arthritis or another inflammatory process than vascular risk, so the value should be repeated after two weeks once the patient is well, and evaluated for a non-cardiovascular cause rather than fed into a risk calculation.
The unit arithmetic is the easy part and still worth stating, because a tenfold error here is consequential in both directions. mg/L is the unit every band and every guideline is written in. A decilitre is a tenth of a litre, so mg/dL is a tenth of the mg/L figure: 3.6 mg/L is 0.36 mg/dL, and a report of 3 mg/dL is 30 mg/L — not a risk band but a modest acute-phase response. µg/mL is numerically identical to mg/L and needs no conversion. A molar unit is not offered, and the reason is instructive rather than evasive: Roche’s inserts do publish one, giving 5 mg/L as 47.6 nmol/L and so a factor of 9.52, but that implies a pentamer of about 105 kDa where the sequence gives closer to 115 kDa and a factor of 8.70. A 9% disagreement about what the molecule weighs is a calibration rather than a conversion, molar reporting of CRP is used nowhere clinically, and the honest thing is to publish both figures in a table and keep neither on the dropdown.
Frequently asked questions
How do I convert hs-CRP from mg/L to mg/dL?
Divide by ten. An hs-CRP of 3.6 mg/L is 0.36 mg/dL, and 1 mg/L is 0.1 mg/dL. Going the other way, multiply by ten — which is why a report of 3 mg/dL is 30 mg/L and means something quite different from 3 mg/L.
Is hs-CRP the same test as CRP?
It is the same molecule and the same units, measured by an assay with a lower working range. Roche’s high-sensitivity assay measures from 0.1 to 20 mg/L and its standard CRP assay from 0.6 to 350 mg/L, both by the same turbidimetric principle and both traceable to the same reference material. Neither is more accurate; they cover opposite ends of the range.
Why is a high-risk hs-CRP still a normal CRP?
Because the cardiovascular bands of 1 and 3 mg/L both sit below the consensus adult reference interval of 5 mg/L. The reference interval describes the spread of a healthy population, while the bands split that same population into thirds by cardiovascular outcome. A value of 4 mg/L is therefore high relative risk and a normal CRP at the same time.
What should I do with an hs-CRP above 10 mg/L?
Stop using it for cardiovascular risk. At that level an acute-phase response is present and is far more likely to be infection, injury, active arthritis or another inflammatory process. Repeat the test about two weeks later once the patient is clinically well, and if it remains unexplained and markedly raised, look for a non-cardiovascular cause.
Does hs-CRP have a molar unit?
Not one that should be used. Roche’s package inserts print nmol/L equivalents implying 9.52 nmol/L per mg/L, from an assumed pentamer mass of about 105 kDa, while the sequence mass of the pentamer is closer to 115 kDa and would give 8.70. Molar reporting of CRP is not in clinical use anywhere, so this converter offers mass units only.
How many hs-CRP samples are needed?
Two, about two weeks apart, both taken when the patient is clinically well, with the average used for risk assessment. A single value is easily shifted by a trivial and unnoticed inflammatory stimulus, and the protein’s half-life of roughly nineteen hours means it tracks the last day or two rather than a baseline.
Related calculators
References
- Pearson TA, Mensah GA, Alexander RW, et al. Markers of inflammation and cardiovascular disease: application to clinical and public health practice. A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation. 2003;107(3):499–511. The publisher’s full text was not accessible; the bands and the >10 mg/L rule quoted here were confirmed from four independent renderings that agree — both Roche package inserts below, StatPearls NBK441843, and a 2015 review in US Pharmacist which also gives the two-samples-two-weeks-apart protocol.
- Roche Diagnostics. Cardiac C-Reactive Protein (Latex) High Sensitive (CRPHS), cobas c method sheet. Measuring range 0.1–20 mg/L (0.952–190 nmol/L); consensus adult reference interval <5 mg/L (<47.6 nmol/L); standardised via the earlier high-sensitive assay to IFCC/BCR/CAP CRM 470.
- Roche Diagnostics. Tina-quant C-Reactive Protein IV, cobas c method sheet. Measuring range 0.6–350 mg/L (5.7–3,332 nmol/L); standardised against IRMM certified reference material ERM-DA474/IFCC.
- UniProt Consortium. UniProtKB P02741 (C-reactive protein): 224-residue precursor of 25,039 Da with an 18-residue signal peptide, in a discoid arrangement of five non-covalently bound subunits.
- Ridker PM, Danielson E, Fonseca FAH, et al. Rosuvastatin to prevent vascular events in men and women with elevated C-reactive protein. N Engl J Med. 2008;359(21):2195–2207.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.