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Below is a breakdown of the ACR calculations.

From National Kidney Foundation: ‘ACR is calculated by dividing albumin concentration in milligrams by creatinine concentration in grams’

Data Example:

Albumin= 43g/L, creatinine= 94µmol/L

However based the ACR formula:

Unit needed for albumin is mg/L, therefore: 43g/L = 43000mg/L

Unit needed for creatinine is g/L: 94µmol/L= 0.000094 mol/L
Molecular weight of creatinine= 113.12g/mol Therefore = 0.000094 mol/L creatinine = 0.000094×113.12 =0.01063528 g/L

Using ACR formula: ACR= 43000/ 0.01063528 = 4043146.9 mg/g

This number was alarming as normal ACR values are below 30 and usually do not go above 300.

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ACR is a useful ratio for urine. See e.g. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2584193/

I suspect your measurements are from serum.

Generally, creatinine is something that is intended to be excreted by the kidneys, and albumin is something not intended to be excreted, so the ratio in urine is going to be heavily in favor of creatinine compared to the ratio in serum. Since creatinine is ordinarily produced at a relatively constant rate and urine volume and concentration varies extremely depending on hydration it's a useful benchmark for measuring concentrations of other things in urine.

It would definitely be abnormal to find an ACR in the urine that matches the serum ACR, that would mean that the kidney is further than merely non-functional, it would be effectively absent entirely except as a leak.

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  • That makes sense, thank you so much! Is there any way to calculate the ACR from the data that I have, or would more data be required? Commented yesterday
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    @SarahSingh If you want to know how kidneys are functioning, you need data from the output of the kidneys. That means you need urine data.
    – Bryan Krause
    Commented yesterday
  • Okay great thank you so much again! Commented yesterday

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