What tests are used to diagnose and monitor IgA nephropathy?

When your doctor suspects Immunoglobulin A (IgA) nephropathy, you will undergo a series of blood and urine tests to map out your kidney health, look for underlying causes, and guide your treatment. While these tests provide a comprehensive picture of how your kidneys are functioning, they cannot definitively diagnose the condition on their own.

The “gold standard” for diagnosing primary IgA nephropathy is a kidney biopsy. However, a biopsy is not automatically performed for everyone. Your doctor will weigh the risks and benefits based on your kidney function, age, and how much protein is in your urine (guidelines often recommend considering a biopsy if protein leakage is 0.5 grams per day or higher) ^[1]. During a biopsy, a small sample of kidney tissue is examined for dominant IgA deposits and graded using a scoring system called the Oxford MEST-C score, which helps predict your risk of future kidney damage ^[2]. A biopsy does carry small risks, such as bleeding, which your nephrologist will discuss with you.

Core Blood and Urine Tests

To evaluate your kidneys and establish a baseline, your medical team will rely on several fundamental tests:

• Urinalysis with microscopy: A laboratory analyzes your urine under a microscope. In suspected IgA nephropathy, doctors look for dysmorphic red blood cells (misshapen red cells) and red-cell casts (cylindrical protein structures containing red blood cells). These findings strongly suggest that bleeding is coming from the glomeruli (the kidney’s filters). While they support the diagnosis of a kidney filter problem, they are not uniquely specific to IgA nephropathy ^[3][4].
• Urine protein-to-creatinine ratio (UPCR) or albumin-to-creatinine ratio (UACR): Instead of collecting all of your urine for 24 hours, doctors often use a single “spot” urine sample to calculate these ratios. They measure total protein (UPCR) or just albumin (UACR) relative to creatinine, and results are reported in units like milligrams per gram (mg/g). Keeping protein leakage low—ideally under 0.5 grams (or 500 mg) per day, and sometimes under 0.3 grams per day—is a key personalized treatment target ^[5][6]. Spot tests only approximate your daily totals, but they are highly useful for predicting outcomes and guiding medications ^[7].
• Serum creatinine and eGFR: A blood draw checks your serum creatinine, a normal muscle waste product. This number is used to calculate your estimated glomerular filtration rate (eGFR), an estimate of your overall kidney filtering capacity. Higher creatinine levels mean a lower eGFR, which indicates reduced kidney function ^[8]. Keep in mind that creatinine can be affected by muscle mass and hydration.
• Electrolytes (including potassium): Routine blood panels check your electrolytes. Maintaining normal potassium is critical for your heart and muscles. Standard blood pressure medications used in IgA nephropathy, like ACE inhibitors or ARBs, can increase potassium levels, requiring close monitoring ^[9]. If specialists prescribe other targeted therapies, such as mineralocorticoid receptor antagonists (like finerenone, which is used in select cases based on evidence), careful potassium checks are also required ^[10].
• Blood pressure: High blood pressure accelerates kidney damage. Your doctor will set an individualized target for you. Guidelines often suggest aiming for a standardized systolic office reading (the top number) below 120 mm Hg, if you can tolerate it safely ^[1][11]. Do not alter your medications based on a single home reading; always follow the personalized plan set by your care team.

Screening for Secondary Causes

IgA nephropathy is usually a “primary” disease, meaning it happens on its own. However, IgA deposits can sometimes be a “secondary” result of other health conditions. Your doctor will use your medical history and symptoms to order targeted screening tests ^[1]:

• Complement tests (C3 and C4): Complement proteins are part of the immune system. Low blood levels of C3 can sometimes indicate a poorer prognosis or raise suspicion for a separate active bacterial infection or alternative kidney condition ^[12][13].
• Infectious disease panels: You may be tested for HIV, Hepatitis B, and Hepatitis C, as these viruses can trigger secondary kidney inflammation ^[14][15].
• Autoimmune markers: Blood tests like ANA or ANCA may be checked. While negative results do not definitively rule out other diseases, these markers help doctors screen for autoimmune conditions like lupus or vasculitis ^[16].
• History-directed evaluations: If you have specific symptoms or risk factors, your doctor might test for celiac disease, inflammatory bowel disease, or liver conditions (like cirrhosis), which are known to cause secondary IgA deposits ^[1][17].

The Importance of Tracking Trends

A single test result rarely tells the whole story; doctors look for trends over time. Persistent blood or high protein in the urine over multiple visits is associated with a higher risk of long-term kidney function loss ^[18][19].

When starting certain kidney-protective medications, like SGLT2 inhibitors, it is common to see a modest, early drop in your eGFR. This is generally an expected shift in kidney pressure rather than actual damage ^[20]. However, a large or continuously dropping eGFR is not expected and could signal dehydration or acute kidney injury, requiring medical review. Repeated testing helps your care team tell the difference between a safe medication effect and a problem.

How Recent Infections Affect Your Results

Many people with IgA nephropathy notice visible blood in their urine (gross hematuria) within a day or two of getting a sore throat, cold, or stomach bug—a common symptom known as synpharyngitic hematuria ^[1][21].

Because of this, test results taken during or immediately after an infection are interpreted carefully. An acute illness can temporarily increase blood and protein in the urine. However, if tests during an infection show a sharp drop in eGFR, unusually heavy protein leakage, or very low C3 levels, your doctor may suspect an overlapping condition called IgA-dominant infection-related glomerulonephritis rather than just a standard IgA nephropathy flare ^[22][23].

When to Contact Your Care Team Promptly

Navigating a new diagnosis and regular monitoring can be stressful, but these tests are designed to catch problems early. Seek prompt medical advice if you experience:

• A rapid or significant decrease in how much urine you are producing.
• New or worsening severe swelling in your legs or face, or severe shortness of breath.
• Persistent visible blood in your urine lasting more than a few days after an infection.
• Severe weakness or palpitations, which can be signs of dangerous potassium changes.
• An acute illness (like severe vomiting or diarrhea) that prevents you from drinking fluids, which can lead to dehydration and acute kidney injury.