Occasionally, when I review a patient’s standard lab test results, their glomerular filtration rate (GFR) tells me they’re slightly dehydrated. I advise the patient that their kidneys are fine and encourage them to drink more water.
But if that patient goes home and Googles their GFR numbers, they may find a National Kidney Foundation (NKF) chart indicating they’re in Stage 2 of chronic kidney disease (CKD). Naturally, the alarmed patient reaches out to me, seeking an explanation.
Are their kidneys actually diseased? No, and I’ll explain!
Detecting Kidney Disease
Kidney disease is a real concern, and we carefully monitor every patient for it.
In years past, we measured its progress based on levels of the waste product creatinine in a patient’s bloodstream. Creatinine results as we digest protein and as our muscles go through normal cycles of breakdown and regeneration. It exits the blood through our kidneys.
A lab score of 1.0 for creatinine was long considered ideal, while anything significantly higher (or lower) was thought to signal kidney problems.
But humans vary in their ratio of muscle mass:
- A strength trainer may have a creatinine ratio of 1.2. Does that warn of potentially abnormal kidney function, or is it simply a normal level given that person’s muscularity?
- In a 96-year-old woman with very little muscle mass, creatinine may measure as low as 0.5. Does that mean her kidneys are compromised?
Because everyone’s body composition is different, medical scientists have determined that creatinine alone isn’t an optimal measure of kidney function. Today, we also rely on a person’s glomerular filtration rate (GFR) to indicate kidney health.
Within our kidneys, tiny nephrons filter waste from the body through our urine. GFR is measured within the filtration tube.
In the same way we look at your blood pressure, we also consider your GFR trends over time. The long-term trend is important because your filtration rate is highly variable. It can rise and fall literally minute by minute.
Dehydration is a primary reason for a rapid drop in GFR. (If we sample your blood and find you’re dehydrated, we could give you a glass of water, and within two minutes, you’d have an improved GFR!)
GFR is also affected by stress levels, fluids (especially caffeine) consumed, and cold medications and anti-inflammatories.
Our Resilient Kidneys
So, what about those stages of chronic kidney disease the NKF established? Is our worried patient in Stage 2 really suffering from kidney disease? Let’s look at the Kidney Foundation guidelines for Stages 1 and 2.
A GFR above 60 typically signifies normal or near-normal kidney function.
- Stage 1 is marked by a GFR of 90 or higher.
- Stage 2 is marked by a GFR between 60 and 90.
Most American adults are in Stage 2, read as “normal” in your metabolic panels.
Of course, if you show up for lab work a bit dehydrated from a recent 5K race, there’s a chance your GFR could temporarily dip to 58 or 59 (slightly into Stage 3) — plus, fasting for your bloodwork may cause an additional drop. But don’t be overly alarmed; GFR changes from minute to minute, and yours will quickly revert back to its normal Stage 2.
The kidneys are among your body’s most resilient organs. Because they’re regularly exposed to various toxins and waste products, they’ve evolved to take a beating and fully recover. Compromised kidneys heal rapidly, helped along by good hydration, medication management, and healthy blood pressure levels.
We Take Kidneys Seriously
Kidney disease seriously hurts a patient’s quality of life, so awareness is key. Your Priority Physicians doctor is here to ensure that these vital organs stay safe and healthy throughout your life.
It’s our mission to keep you informed about your metabolic panel results and what they mean. We keep an eye on your lab work and GFR numbers, and — well before symptoms arise — we’ll alert you to any shifts in your kidney health that we should manage together.
You can always contact our doctors with questions about your tests. Give us a call; we’re happy to talk.
