I am a female recently completed a 24 hour catch. My creatinine serum was 1.06 & GFR 56. 3 weeks prior GFR was 59. Should I be concerned?

Tests vary. so the difference between 56 and 59 isn't meaningful BUT that is a bit abnormal for a person 55 or younger. So, some reason for concern if you dont' already know why youe kidneys are being studied so closely.