My father had a radical nephrectomy 3 years back. he lost one kidney. recently tests shown his creatinine level 2.0. not diabetic. how to lower down?

See answer: Way to preserve remaining renal function include: avoid/restrict use of medications that may adversely affect the kidneys such as nsaids (e.g. Ibuprofen, naproxen), staying well hydrated, keeping blood pressure and diabetes if present well-controlled, avoid tobacco; follow any dietary limitations (excessive protein intake), and regular check-ups with your physician and/or a nephrologist.

Follow-up: If dad is a well-muscled man (which raises creatinine well above "normal range" for today's couch potatoes) and we already know why he lost half his nephrons, this may not be an issue. I trust he is being followed up and that folks are watching for focal-segmental glomerulosclerosis / hyperfiltration lesion that's fairly common in kidneys that lose their partner. Don't try to treat a lab value.