Just curious about the type of doctor that told you this..... My diabetic doctor discovered in my annual check up that my eGFR had dropped to 35 at age 75 (stage 3B), although my diabetes seemed stable. She quickly referred me to a nephrologist who also had me consult with a dietician online for several months. He made one change in my existing meds by cutting dosage of a blood pressure med. Now it is one year later and I gradually managed to claw up to 65 which is low stage 2. Fingers crossed the improvement will continue.

Can you question your doctor further, or perhaps go to a nephrologist on your own without a referral?