Stage 2 kidney disease means your kidneys are filtering blood at a slightly reduced rate, with a glomerular filtration rate (GFR) between 60 and 89 mL/min. On its own, a GFR in that range doesn’t qualify as chronic kidney disease. You only meet the criteria for stage 2 CKD if there’s also evidence of kidney damage, such as protein leaking into your urine. The causes range from common chronic conditions like diabetes and high blood pressure to less obvious factors like autoimmune diseases, inherited conditions, and long-term medication use.
Why GFR Alone Doesn’t Tell the Whole Story
A GFR between 60 and 89 is only mildly below the normal range of 90 or higher, and many healthy people, especially older adults, fall into this zone without any actual kidney damage. For a stage 2 diagnosis, your doctor needs a second piece of evidence: typically a urine test showing elevated albumin, a protein that healthy kidneys keep in the blood. A normal urine albumin-to-creatinine ratio is below 30 mg/g. Anything above that threshold, confirmed on at least two tests over three months, signals that something is injuring the kidneys’ filtering units even while overall function remains relatively preserved.
About 2.75% of U.S. adults meet the criteria for stage 2 CKD based on national survey data from 2017 to 2020. That’s a smaller group than you might expect, precisely because a mildly reduced GFR alone isn’t enough for the diagnosis.
Diabetes: The Most Common Cause
Persistently high blood sugar is the leading driver of kidney damage worldwide. When glucose stays elevated over months and years, it reacts with proteins in your blood to form compounds called advanced glycation end products. These compounds trigger inflammation, generate oxidative stress, and cause collagen fibers in the kidney to cross-link and stiffen. The result is a gradual thickening of the membranes inside the kidney’s filtering units (glomeruli), which impairs their ability to selectively filter waste while retaining useful proteins.
One of the earliest signs of diabetic kidney damage is albumin appearing in the urine, often long before GFR drops significantly. Specialized cells called podocytes, which wrap around the kidney’s tiny blood vessels and help control what passes through the filter, begin to malfunction and die off. This is why routine urine screening is so important for people with either type 1 or type 2 diabetes. Stage 2 CKD from diabetes is highly treatable when caught early, but the damage is cumulative and typically silent.
High Blood Pressure and Blood Vessel Damage
Chronic high blood pressure is the second most common cause. The kidneys depend on a dense network of tiny arteries to deliver blood for filtering, and sustained hypertension damages those vessels in two ways. The walls of small arteries thicken as smooth muscle cells multiply, and plasma proteins seep into the vessel walls, creating a waxy buildup called hyalinosis. Both changes narrow the arteries and reduce blood flow to the nephrons, the kidney’s functional units.
Over time, reduced blood flow starves kidney tissue and damages the glomeruli and surrounding structures. This process, called hypertensive nephrosclerosis, tends to progress slowly. Many people have no symptoms at all in the early stages, which is why blood pressure control is one of the most effective ways to slow or prevent kidney disease progression.
Autoimmune and Inflammatory Conditions
Your immune system can directly attack the kidneys’ filtering units, a group of conditions collectively called glomerulonephritis. Several specific types are worth knowing about:
- IgA nephropathy: Deposits of an immune protein called IgA accumulate in the glomeruli and trigger chronic, low-grade inflammation. This is one of the most common forms of glomerulonephritis, and the damage often goes undetected for years because it causes few obvious symptoms early on.
- Lupus: This systemic autoimmune disease can inflame many organs, including the kidneys. Lupus nephritis occurs when immune complexes lodge in the glomeruli and provoke an inflammatory response.
- Post-streptococcal glomerulonephritis: A week or two after a strep throat or skin infection, antibodies to the bacteria can accumulate in the glomeruli and cause inflammation. This form often resolves on its own in children but can leave lasting damage in adults.
Viral infections also play a role. Hepatitis B, hepatitis C, and HIV can all cause glomerular inflammation and progressive kidney damage, sometimes before other symptoms of the infection become apparent.
Polycystic Kidney Disease
Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited cause. Fluid-filled cysts grow throughout both kidneys over decades, gradually compressing and destroying normal tissue. What makes ADPKD tricky in the context of stage 2 CKD is that kidney volume can increase substantially before GFR drops. The kidneys compensate for early cyst damage by working harder in their remaining healthy tissue, so by the time GFR falls into the 60 to 89 range, significant structural damage may already be present.
Doctors use kidney imaging alongside GFR to assess how quickly ADPKD is likely to progress. Total kidney volume relative to height, combined with the patient’s age and known genetic mutations, helps predict whether someone is on a fast or slow track toward more advanced kidney failure.
Recurrent Infections and Urinary Obstructions
Repeated or untreated kidney infections (pyelonephritis) leave behind patches of scar tissue in a distinctive, irregular pattern. Each episode of infection destroys a small area of kidney tissue, and over years, the cumulative scarring reduces overall function. When chronic pyelonephritis affects both kidneys, chronic kidney disease often follows.
The underlying cause is usually a structural problem that allows bacteria to travel upward from the bladder into the kidneys. Kidney stones, an enlarged prostate, congenital abnormalities of the urinary tract, and neurogenic bladder (where nerve damage prevents normal bladder emptying) all create conditions that make infections more likely and harder to clear. Removing or managing the obstruction is key to preventing further scarring.
Medications and Over-the-Counter Pain Relievers
Regular, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen can damage the kidneys by reducing blood flow to them. Short courses for acute pain carry minimal risk in healthy people, but prolonged use or high doses, especially without medical supervision, can cause cumulative injury. The risk is higher if you already have even mildly reduced kidney function, because the kidneys depend on the very blood flow pathways that NSAIDs suppress.
Other medications can contribute to kidney damage as well, including certain antibiotics, proton pump inhibitors used for acid reflux, and some chemotherapy drugs. The common thread is that any substance filtered through the kidneys has the potential to cause harm if the dose is high enough, the duration long enough, or the kidneys already vulnerable.
Other Contributing Factors
Several additional conditions increase the likelihood of progressing to or being diagnosed with stage 2 CKD. Obesity places extra metabolic demand on the kidneys and contributes to the development of both diabetes and hypertension. Smoking damages blood vessels throughout the body, including those supplying the kidneys. A family history of kidney disease raises your baseline risk independent of other factors.
Age itself plays a role: GFR naturally declines with age, and an older adult with a GFR of 65 may simply be experiencing normal aging rather than disease. The distinction depends entirely on whether there’s evidence of actual kidney damage, like persistent protein in the urine, abnormal kidney structure on imaging, or a history of a condition known to harm the kidneys. This is why stage 2 CKD always requires context, not just a number on a lab report.