Can gfr be low if i has not had a drink of for about 14 hrs before the blood test? result=85.1ml/min/1.73 m2 thx

GFR and dehydration: You can have a low GFR due to dehydration and the figure of 85 ml/min is an estimated gfr. You did not mention your bun, sodium, chloride or creatinine and that would have been helpful in determining if you were really dehydrated. Ask your doctor to order a 24 hour urine for creatinine clearance and protein and that will tell you exactly what your GFR is, actually not estimated.