THE SEMI-COMPLETE USER'S GUIDE TO...YOUR KIDNEYS

Protein's bad! You're drinking too much water (or maybe not enough?)! Our experts set the record straight on what keeps these filters going.

- KEVIN DUPZYK

WHAT THEY DO

THE KIDNEYS HAVE a few important jobs, but primarily they're waste-removal experts. Inside your kidneys, blood passes through filtering units called nephrons. The nephrons remove excess nutrients like salts and potassium and send them to the bladder to be peed out.

HOW TO KNOW IF THEY'RE OKAY OR NOT

YOU CAN HAVE pretty advanced kidney problems without any symptoms, says Blaise Abramovitz, D.O., a nephrologist with the University of Pittsburgh Medical Center Mercy Hospital.

If waste buildup and high blood pressure reduce these organs' function, you can end up with fatigue, shortness of breath, and swelling, especially in the feet and ankles. Kidney decline is often permanent, leading to the need for dialysis or an organ transplant. That's why two blood tests-one for creatinine and another for eGFR-are crucial steps in any diagnosis:

CREATININE is a waste product of muscle metabolism that your kidneys should filter out of your blood; this test measures the remainder. A high number (above 1.35 mg/dL for men) is bad. If you have a lot of muscle or take creatine, your blood may undergo other tests that account for this.