GFR does go down with age

DEAR DR. ROACH » Each year when I receive results from my bloodwork I notice that my GFR score keeps going down.

This year is the first year that my score dropped below 60, with a score of 57.

I am 66 years old, and there are no other scores in my bloodwork that would indicate kidney disease.

My doctor keeps telling me to just drink more water. I take amlodipine/ benazepril for my blood pressure.

Should I be concerned and have further tests? Is the blood pressure medication causing my GFR score to be low?

— A.S.

DEAR READER »

GFR, the glomerular filtration rate, is a measure of kidney function, with the higher the number meaning the greater the kidney function. It’s calculated using a person’s age and sex, and the measured creatinine in the blood. Creatinine is cleared from the blood by the kidneys, so the lower the creatinine, the higher the GFR and the better the kidney function.

Kidney function slowly goes down as we age, but the rate of decline is important. The average GFR for a person in their 60s is about 85, but you are on a medication (benazepril) that lowers the GFR number.

In the kidney, benazepril (a class of medication called an ACE inhibitor) decreases blood flow to the filtering parts of the kidney, the glomeruli, and creatinine always goes up.

However, ACE inhibitors are excellent at protecting kidney function in people with many kinds of kidney diseases.

Stopping it would make the number look better but would rob you of the protection the medication is giving you.

Your regular doctor can tell you whether your rate of GFR decline is worth worrying about. If not, a kidney specialist will certainly do so. It is wise to look carefully at your other medicines, if any, especially including overthe-counter pain medicines, to make sure none of them could be harming your kidneys.