Glomerular filtration rate (GFR) is a measure of kidney function.

Most test results from a laboratory are directly measured values. GFR is not. It is calculated based on the value of a directly measured blood test called creatinine. The blood creatinine value is plugged into a formula that also includes age, gender and sometimes body weight.

Because it is a calculation rather than a direct measurement, there is more room for error. Most lab reports use "greater than 60" as normal for GFR.

Review your laboratory report for the values of blood urea nitrogen (BUN) and creatinine. If the BUN and creatinine are normal, then the lower than expected GFR might indeed be inaccurate.

I would recommend a urine analysis test, if not already done. I would also recommend that you repeat your blood work in 3 to 6 months just to be sure you are not developing any kidney problems.