Healthy kidneys filter about 50 gallons of blood every day, removing waste and excess fluid without you ever noticing. The clearest way to confirm they’re working well is through two simple tests: one blood test that estimates your filtration rate, and one urine test that checks for protein leakage. But your body also offers several everyday signals, from how your urine looks to whether your rings fit tighter than usual, that can hint at kidney trouble before you ever step into a lab.
The Two Tests That Matter Most
Kidney health comes down to two core questions: How well are your kidneys filtering blood? And are they leaking things they shouldn’t? A standard blood panel and a urine sample can answer both.
The blood test measures your eGFR (estimated glomerular filtration rate), a score that reflects how efficiently your kidneys clean your blood. A healthy eGFR is around 100, though it naturally declines with age. Average values for someone in their 20s sit around 116, while someone over 70 typically lands around 75, and both are considered normal. An eGFR that stays below 60 for three months or more is the standard threshold for a chronic kidney disease diagnosis. The lowest possible score is zero, meaning the kidneys have stopped working entirely.
The urine test measures your albumin-to-creatinine ratio (UACR), which detects tiny amounts of protein escaping into your urine. Healthy kidneys keep protein in the bloodstream where it belongs. A UACR above 30 mg/g signals that your kidneys’ filters are letting protein slip through, a condition called albuminuria and an early marker of kidney damage. Levels between 30 and 300 mg/g indicate moderate leakage, while anything above 300 mg/g suggests more significant damage. Many people with early kidney disease feel completely fine, which is why this test catches problems that symptoms alone can miss.
Your doctor may also check your blood urea nitrogen (BUN), a waste product your kidneys normally clear. The typical adult range falls between 6 and 24 mg/dL. Levels above 100 mg/dL indicate seriously impaired kidney function.
What Your Urine Can Tell You
You don’t need a lab to start paying attention to your kidneys. Your urine offers daily clues.
Foamy urine is one of the most commonly searched kidney symptoms, and occasional bubbles after a strong stream are normal. What’s worth noting is persistent foam, especially if it looks thick and white like the head on a root beer float, or if the bubbles don’t disappear after a flush or two. That kind of froth typically signals excess protein in the urine, which means your kidney filters may be compromised.
Volume and frequency matter too. A healthy adult with normal fluid intake produces roughly 800 to 2,000 milliliters of urine per day. A noticeable and sustained drop in output, or a dramatic increase (especially waking multiple times at night to urinate when that’s not your norm), can reflect changes in kidney function. Color is another quick indicator: pale yellow suggests adequate hydration, while consistently dark urine may mean your kidneys are concentrating waste more than usual.
Swelling in Specific Places
When kidneys can’t remove enough fluid or they leak too much protein, fluid accumulates in your tissues. This swelling, called edema, tends to show up in predictable locations: around your eyes (especially in the morning), in your hands, and in your feet and ankles. Puffy eyes that don’t resolve after you’ve been upright for a while, shoes that suddenly feel tight, or indentations left in your skin after pressing on your shins are all patterns worth tracking. The swelling happens because protein loss from damaged kidneys lowers the protein concentration in your blood, and that shift lets fluid seep out of blood vessels into surrounding tissue.
Blood Pressure and Kidney Health
Your kidneys and blood pressure exist in a feedback loop. Kidneys help regulate blood pressure by controlling fluid volume and releasing hormones that tighten or relax blood vessels. When blood pressure runs too high, it damages the tiny blood vessels inside the kidneys, reducing their filtering capacity. That damage, in turn, can push blood pressure even higher.
Keeping blood pressure below 140/90 mm Hg is the general target for protecting kidney function. If you already have some kidney damage, your target may be lower. Consistently elevated readings, even if you feel fine, represent one of the most significant and modifiable risks to long-term kidney health. A blood pressure cuff at home, used regularly, gives you a practical way to monitor one of your kidneys’ biggest threats.
Skin Changes and Persistent Itching
Unexplained itching that doesn’t come with a visible rash can be a late-stage signal of kidney problems. When kidneys lose filtering efficiency, waste products build up in the bloodstream. This buildup can trigger intense, widespread itching that isn’t localized to one area and often worsens when the skin is dry. Unlike a typical allergic reaction or eczema, there’s no rash or visible skin change that explains the itch. This symptom is most common in people with advanced or end-stage kidney disease, so it’s not an early warning sign, but it’s one that often goes unrecognized because people don’t associate itching with their kidneys.
Other Subtle Signs Worth Knowing
Kidney problems can produce a range of vague symptoms that overlap with many other conditions. Persistent fatigue is common because struggling kidneys produce less of the hormone that stimulates red blood cell production, leading to anemia. A metallic taste in the mouth or loss of appetite can develop as waste products accumulate in the blood. Feeling unusually cold, even in warm environments, is another anemia-related signal. Difficulty concentrating, muscle cramps (particularly at night), and trouble sleeping round out the less obvious signs.
None of these symptoms on their own confirm kidney disease. They become meaningful when several cluster together, when they persist without another clear explanation, or when they appear alongside risk factors like diabetes, high blood pressure, a family history of kidney disease, or being over 60.
How to Track Kidney Health Over Time
Kidney disease is often called a silent condition because most people lose a significant portion of kidney function before they notice anything wrong. Routine blood work that includes eGFR and a urine test for albumin are the most reliable way to catch problems early. If you have diabetes, high blood pressure, or a family history of kidney disease, annual screening is standard practice.
Between lab tests, you can monitor several things at home: check your blood pressure regularly, note changes in urine appearance or frequency, watch for unexplained swelling, and stay aware of persistent fatigue. Staying well-hydrated, keeping blood pressure in range, managing blood sugar if you have diabetes, and limiting regular use of over-the-counter pain relievers (which can stress the kidneys over time) are the most effective everyday strategies for keeping your kidneys healthy long-term.
If your eGFR comes back between 60 and 89 with no protein in your urine, you likely have normal, age-appropriate kidney function. An eGFR above 90 with a UACR below 30 mg/g is a clean bill of health for your kidneys. Those two numbers, checked periodically, are the most concrete answer to whether your kidneys are doing their job.