Dear "Sotis",
Your age in itself would not be a problem if you are healthy (I donated at 56, 9 years ago). But as Sherri noted above, diabetis is one of the main destroyers of kidneys, so they would want to check very carefully. They would not want you to donate and then yourself need a transplant later. Also, make sure with your mon's doctors that she is a good candidate to receive a transplant. Not all patients on dialysis are able to receive a transplant, due to other health problems. If she is a good candidate to receive a transplant, but you are not accepted for health reasons, get the word out to friends, relatives, church/synagogue members, neighbors, former co-workers and alumni etc. as there may be other people in their 50's or 60's in good health who would want to donate if they knew of the need.
best wishes,
Fr. Pat