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Kidney Function
kcpoe posted:
My family members' doctor told her her kidney function is at 40%. The doctor has only done bloodwork, no other tests. How could he come up with this number?
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mrscora01 responded:
There are specific blood tests that test kidney function. Things like creatinine and urea as well as electrolyte levels will indicate how well your kidneys are working.

john-skpt responded:
The number that he gave is not really a "percentage" value, but most docs treat it that way. This is an eGFR, e for estimated, glomerular filtration rate for GFR. The key word here is "estimated". The number should really be expressed as ml/min/1.72 meters squared, not as 'percent', but no doc wants to try to make a patient understand that; it's just too complex. So they oversimplify and call it "percent". This estimated number is calculated only from blood numbers, so it is a bit less accurate that test that compare blood and urine values.

A true measurement for GFR is somewhat tedious and time consuming to do, so most docs rely on the fast and easy eGFR. And in most cases, the results are good enough.

All of that said, and recalling that the number is not really 40 percent on a 0-100% scale, but 40 ml/min on a scale that really tops out at about 60 ml/min, 40 is somewhat reduced from the ideal level. Also bear in mind that everybody naturally loses a bit of renal function with age, so that needs to be accounted for. A level of 40 in an 80 year old is less of a concern than a level 40 in a 20 year old.

It probably does merit attention, if only to eliminate or reduce potential causes of additional damage in coming years.

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