Your kidneys work quietly in the background to keep your body balanced and healthy. They filter your blood to remove waste, extra fluid, and chemicals you don’t need—turning them into urine. They also help control your blood pressure, keep your bones strong, and make a hormone that helps your body produce red blood cells. When your kidneys are working well, you usually don’t notice them at all. But if they start to struggle, waste and fluid can build up, leading to symptoms like tiredness, swelling, or changes in your urine. That’s why it’s important to keep an eye on kidney health, especially if you have risk factors like high blood pressure or diabetes. Early checks can help catch problems before symptoms appear and give you more options to protect your health.
We measure kidney function using a test called the estimated glomerular filtration rate, or eGFR. This tells us how much blood plasma your kidneys filter each minute—specifically, how many millilitres pass through the glomeruli (the tiny filtering units in your kidneys) every minute. A normal GFR is around 90 to 120 mL per minute per 1.73 m² of body surface area. That might sound small, but over a full day, your kidneys filter about 180 litres of plasma—even though your total plasma volume is only around 3 litres. This means your plasma is filtered and reprocessed many times each day to keep your body in balance. We calculate eGFR using a blood test that measures creatinine, along with your age, sex, and body size. It’s a simple but powerful way to track how well your kidneys are working over time.
This constant filtering and rebalancing is what allows your body to stay stable even when you’re eating, exercising, or dealing with illness. Your kidneys adjust to what your body needs—holding onto water when you’re dehydrated, releasing extra salt when you’ve had too much, and clearing waste products that build up from food and muscle activity. They also help manage acid levels to keep your blood from becoming too acidic or too alkaline. All of this happens automatically, without you needing to think about it. When kidney function drops, these adjustments become harder, and small imbalances can turn into bigger health problems. That’s why understanding what your kidneys do—and checking how well they’re working—is such an important part of staying well.
If you’re unsure about your kidney function or want to learn more, speak with your GP or book an appointment with Western Nephrology today.
