hs-CRP:Albumin Ratio Calculator
The CRP-to-albumin ratio (CAR) combines two routine lab values into a composite marker studied as a signal of inflammatory burden and nutritional status. It appears mainly in prognosis research — this page helps you compute it and see where your number sits against general-population data.
High-sensitivity C-reactive protein
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How it works
The formula — and the units trap
This page computes CRP (mg/L) ÷ albumin (g/dL). Beware: published studies use different unit conventions (CRP in mg/dL or mg/L, albumin in g/dL or g/L), which shift cut-off values by an order of magnitude. Cut-offs from the literature are not directly interchangeable — always check the units before comparing.
What this marker is — and is not
CAR combines an inflammation marker (CRP) with a protein that falls during inflammation and poor nutrition (albumin). It is studied mainly as a prognostic factor in oncology, critical care, and inflammatory bowel disease. There is no official reference interval for healthy people — the bands here are anchored to the distribution in a large US adult population sample (NHANES), which we state openly rather than implying false precision.
hs-CRP vs standard CRP
High-sensitivity CRP and standard CRP measure the same analyte; hs-CRP is simply more precise at low concentrations. Most CAR research used standard CRP in disease cohorts, while hs-CRP is what wellness panels typically report. At the low end of the range this distinction matters less than the units issue above.
Limitations
A single CRP value can spike from a cold, a hard workout, or a dental infection, and albumin shifts with hydration, liver function, and nutrition. One ratio on one day is a weak signal; trends and clinical context are what give it meaning.
Frequently asked questions
What is a normal CRP/albumin ratio?
There is no official reference interval for the general population — anyone who claims otherwise is overstating the evidence. As a rough anchor, in a large US adult sample the middle 50% of values fell roughly between 0.15 and 0.7 (CRP mg/L ÷ albumin g/dL). Interpret your number with your doctor.
Why combine CRP with albumin?
They move in opposite directions during systemic inflammation: CRP rises, albumin tends to fall. The ratio amplifies that combined signal, which is why researchers find it tracks outcomes in serious illness cohorts better than either value alone.
Is the CRP/albumin ratio a diagnostic test?
No. It is a research-stage composite marker used mainly in prognosis studies. It does not screen for or diagnose any condition, and this tool does not interpret your lab report — that is your physician's role.
My CRP is in mg/dL — how do I convert?
Multiply mg/dL by 10 to get mg/L. Note that mixing up units is the most common error with this ratio — published cut-offs from studies may use yet other conventions, so compare carefully.
What can raise my ratio temporarily?
Any recent infection or inflammation — a cold, a dental issue, intense exercise, minor injury. Albumin also dips with dehydration and poor protein intake. If your result surprises you, retesting when you are well is often the most sensible next step.
Sources
- Sayar S, Kurbuz K, Kahraman R, et al. A practical marker to determining acute severe ulcerative colitis: CRP/albumin ratio. North Clin Istanb, 2020.
- Yu Q, Li KZ, et al. Clinical significance and prognostic value of C-reactive protein/albumin ratio in gastric cancer. Ann Surg Treat Res, 2021.
- The C-reactive protein-to-albumin ratio as a diagnostic biomarker for rheumatoid arthritis: a cross-sectional NHANES analysis. Front Med, 2025.
This calculator is for informational purposes only and is not medical advice, diagnosis, or treatment. Reference ranges are general population guidelines — always discuss your lab results with a qualified healthcare professional.