Diagnosing nephropathy, particularly when caused by diabetes, involves a combination of regular screening tests and clinical evaluations that help catch kidney damage early—often before symptoms appear. Early detection is crucial because it opens the door to treatments that can slow or even halt the progression of kidney disease, preventing serious complications like kidney failure.
Introduction: Who Should Seek Diagnostic Testing
If you have been diagnosed with diabetes—whether type 1 or type 2—you should undergo regular diagnostic testing for nephropathy, which refers to kidney disease or damage. About one in three people living with diabetes develop diabetic nephropathy, making it the most common cause of kidney failure in developed countries.[1][3] This condition develops when high blood sugar levels over time damage the tiny blood vessels and filtering units inside the kidneys, impairing their ability to remove waste and excess fluid from the body.[4]
Anyone with diabetes should begin screening at specific times. If you have type 2 diabetes, you should be tested at the time of diagnosis and every year thereafter. If you have type 1 diabetes, screening should start once you’ve had the condition for more than five years, and then continue annually.[6][8] This regular testing is essential because in the early stages of nephropathy, there are usually no noticeable symptoms. By the time symptoms such as swelling, fatigue, nausea, or shortness of breath appear, the kidneys may already be significantly damaged—often 80% to 90% of kidney function may be lost.[5][9]
You are at higher risk for developing diabetic nephropathy if you also have high blood pressure, heart disease, a family history of kidney disease, high cholesterol, or if you use tobacco products. Certain ethnic groups, including Black, Native American, Alaska Native, Polynesian, and Maori populations, are also at greater risk.[5][9] If any of these risk factors apply to you, discussing regular kidney testing with your doctor is particularly important.
Classic Diagnostic Methods
Diagnosing nephropathy, particularly diabetic kidney disease, relies on routine screening tests that are simple, non-invasive, and highly informative. These tests are typically part of regular diabetes care and help doctors assess how well your kidneys are functioning and whether any damage has occurred.
Urinary Albumin Test
One of the primary tests used to detect early kidney damage is the urinary albumin test. This test checks for the presence of a blood protein called albumin in your urine. Normally, healthy kidneys do not allow albumin to pass from the blood into the urine. When the filtering units in the kidneys become damaged—as can happen with diabetes—albumin begins to leak through, appearing in the urine. This is one of the earliest signs that the kidneys are not working as they should.[6]
The test is usually performed on a spot urine sample, meaning you simply provide a small amount of urine during your doctor’s visit. Finding albumin in the urine, especially in repeated tests, indicates that kidney function may be declining and that intervention is needed.
Albumin-to-Creatinine Ratio (ACR)
To get a more accurate picture of kidney health, doctors often use the albumin-to-creatinine ratio, or ACR. This test compares the amount of albumin in your urine to the amount of creatinine, a waste product produced by muscles that healthy kidneys normally filter out of the blood.[6] The ratio helps healthcare providers understand how much albumin is being lost relative to normal waste removal, giving a clearer sense of kidney function.
An elevated ACR suggests that your kidneys are not filtering properly. Depending on the level of albumin detected, kidney damage can be classified as moderate (microalbuminuria, with 30 to 300 mg of albumin per day) or severe (macroalbuminuria, with more than 300 mg per day).[7] The ACR is a key marker used not only for diagnosis but also for monitoring disease progression over time.
Estimated Glomerular Filtration Rate (eGFR)
Another critical test is the estimated glomerular filtration rate, or eGFR. This test measures how well your kidneys are filtering blood. It is calculated based on the level of creatinine found in a blood sample, along with factors such as your age, sex, and sometimes race.[6][9] The eGFR gives an estimate of how much blood your kidneys filter each minute.
A normal eGFR is around 100, meaning your kidneys are filtering efficiently. As kidney function declines, the eGFR number drops. A low eGFR indicates that the kidneys are not working well and that waste products are building up in the blood. The eGFR is used to stage chronic kidney disease from Stage 1 (mild damage with eGFR of 90 or higher) to Stage 5 (kidney failure with eGFR below 15).[5][9]
Blood Creatinine Test
The blood creatinine test measures the level of creatinine in your blood. Creatinine is a waste product that accumulates when kidneys are not filtering blood effectively. High levels of creatinine in the blood suggest reduced kidney function. This test is often used in combination with the eGFR calculation to assess kidney health.[6]
Imaging Tests
In some cases, your doctor may order imaging tests to get a visual look at your kidneys. X-rays, ultrasound, CT scans, or MRI scans can show the size and structure of the kidneys and help identify any blockages, abnormalities, or changes in blood flow within the kidneys.[6] These tests are especially useful if your doctor suspects structural problems or needs to rule out other causes of kidney damage.
Ultrasound is a common and non-invasive imaging tool that uses sound waves to create pictures of the kidneys. CT and MRI scans provide more detailed images and can assess how well blood is moving through the kidneys, which is important for understanding the extent of damage.
Kidney Biopsy
In certain situations, a kidney biopsy may be performed. This procedure involves using a thin needle to remove a small sample of kidney tissue, which is then examined under a microscope in a laboratory. A biopsy can reveal the specific type and extent of kidney damage and help distinguish diabetic nephropathy from other types of kidney disease.[6]
The procedure is typically done using a local anesthetic to numb the area, and imaging tools such as ultrasound are used to guide the needle to the correct location. While a biopsy is more invasive than blood or urine tests, it provides valuable information when the diagnosis is unclear or when other tests show unexpected results.
Diagnostics for Clinical Trial Qualification
For patients who are interested in participating in clinical trials, additional or more frequent diagnostic testing may be required. Clinical trials are research studies that test new treatments, medications, or approaches to managing kidney disease. To determine whether a patient is eligible for a specific trial, researchers use standardized diagnostic criteria to assess kidney function and disease progression.
Albuminuria Assessment
Clinical trials for diabetic nephropathy often use albuminuria levels as a key criterion for enrollment. Researchers may require that participants have a certain level of albumin in their urine—such as moderate albuminuria (30 to 300 mg per day) or severe albuminuria (more than 300 mg per day)—to qualify for the study.[7] Repeated measurements of albumin levels may be needed to confirm that the condition is persistent and not due to temporary factors like infection or physical activity.
Glomerular Filtration Rate Staging
The eGFR is also commonly used to classify patients into specific stages of chronic kidney disease for clinical trial purposes. Trials may focus on patients in early stages (such as Stage 1 or 2) to test preventive therapies, or on patients in later stages (Stage 3, 4, or 5) to evaluate treatments aimed at slowing progression to kidney failure.[9] Accurate eGFR measurements help ensure that trial participants have similar levels of kidney function, making it easier to assess the effectiveness of the treatment being studied.
Blood and Urine Biomarkers
In addition to standard tests, some clinical trials may use newer or experimental biomarkers—substances in the blood or urine that indicate disease activity or progression. Traditional markers like albumin and creatinine are relatively insensitive and may not detect kidney damage until it is quite advanced. Researchers are exploring novel biomarkers that could identify kidney disease earlier and more accurately.[3]
These biomarkers might include specific proteins, enzymes, or other molecules that are released when kidney tissue is injured. While not yet part of routine clinical practice, these tests are being studied in clinical trials to determine their usefulness in diagnosing and monitoring nephropathy.
Blood Pressure and Glycemic Control Monitoring
Because managing blood pressure and blood sugar levels is critical in treating diabetic nephropathy, clinical trials often require detailed monitoring of these factors. Participants may need to have their blood pressure measured at every visit and maintain it below certain targets, such as less than 140/90 mm Hg.[8] Blood sugar control is also closely tracked, often through A1C testing, which measures average blood sugar levels over the past two to three months.
These measures help researchers understand whether improvements in kidney function are related to the treatment being tested or to better control of diabetes and blood pressure.
Additional Tests for Complications
Clinical trials may also screen for complications associated with chronic kidney disease, such as anemia, high potassium levels, high phosphorus levels, or bone disease. Blood tests to check levels of hemoglobin (to detect anemia), potassium, phosphorus, and parathyroid hormone (related to bone health) may be required for enrollment or during the course of the study.[11]
Understanding these complications is important because they can affect a patient’s overall health and response to treatment. Trials often aim to address not just kidney function but also the broader impact of kidney disease on the body.
