You should see a nephrologist when your kidney function drops below certain thresholds, when protein or blood appears in your urine, or when conditions like diabetes and high blood pressure begin affecting your kidneys. Most people are referred by their primary care doctor based on blood and urine tests, but knowing the specific triggers can help you advocate for yourself if something looks off.
A nephrologist is a doctor who specializes in the medical care and function of your kidneys. They manage kidney disease, kidney-related high blood pressure, electrolyte problems, and kidney failure. They’re distinct from urologists, who focus on the urinary tract and bladder, as well as the male reproductive system. If the issue is about how well your kidneys filter blood and manage waste, a nephrologist is the right specialist.
The Key Lab Numbers That Trigger a Referral
Two routine tests drive most nephrology referrals: your estimated glomerular filtration rate (eGFR), which measures how well your kidneys filter blood, and your urine albumin-to-creatinine ratio (UACR), which measures how much protein is leaking into your urine.
Most major guidelines, including those from the National Kidney Foundation and international kidney disease organizations, recommend referral when your eGFR drops below 30 mL/min. A normal eGFR is around 90 or higher, so 30 represents a significant loss of kidney function (stage 4 kidney disease). Some countries, like France, use a higher cutoff of 45, and several guidelines recommend referral at eGFR levels between 30 and 60 if your kidney function is declining rapidly, generally defined as a drop of more than 5 points per year.
Age matters here. If you’re younger than 55, some guidelines suggest referral when eGFR falls below 60, especially if protein is also present in your urine. For people over 75, the threshold may be lower because some decline in kidney filtration is expected with aging. Your doctor should be interpreting your eGFR in the context of your age and overall health, not just as an isolated number.
For urine protein, the critical number is a UACR above 300 mg/g, which indicates significant protein leakage and kidney damage. Even levels between 30 and 300 mg/g (sometimes called microalbuminuria) are a warning sign, particularly when combined with a declining eGFR. If your UACR is above 300, referral is recommended regardless of your eGFR.
Diabetes and Kidney Damage
Diabetes is the leading cause of kidney failure, so people with diabetes face specific referral criteria. The American Diabetes Association recommends referral when eGFR drops below 30 or when urine albumin exceeds 300 mg/g. But there are earlier warning signs your doctor should be watching for: a sudden drop in eGFR of more than 25% from your baseline, potassium levels above 5.5 or below 3.5, or anemia linked to kidney disease.
If you have diabetes and your kidney numbers are changing quickly, or if your doctor isn’t sure whether diabetes is actually causing the kidney problem, that uncertainty alone is reason enough for a nephrology referral. Not all kidney disease in people with diabetes is caused by diabetes, and a nephrologist can help sort out what’s driving the damage.
Blood Pressure That Won’t Come Down
High blood pressure and kidney disease fuel each other. Poorly controlled blood pressure damages the kidneys, and damaged kidneys make blood pressure harder to control. If your blood pressure stays above your target despite taking three or more medications at their optimal doses, including a diuretic (water pill), you have what’s called resistant hypertension. This is a strong reason to see a nephrologist.
Patients with uncontrolled blood pressure are more likely to develop progressive kidney disease, and the kidneys may be both the cause and the casualty. A nephrologist can evaluate whether an underlying kidney problem is driving the resistance and adjust treatment accordingly.
Physical Symptoms Worth Paying Attention To
Kidney disease is often called a “silent” condition because it can progress without obvious symptoms for years. But certain physical changes are red flags:
- Foamy urine. Occasional bubbles are normal, but persistently foamy urine often signals protein leaking through damaged kidney filters.
- Blood in your urine. Visible blood can come from the kidneys, bladder, or urinary tract. Your doctor may refer you to a nephrologist or urologist depending on the suspected cause.
- Puffy eyes. Swelling around the eyes, especially in the morning, can be one of the earliest visible signs that your kidneys are leaking protein.
- Swollen ankles or feet. When kidneys can’t remove enough fluid and sodium, fluid accumulates in the lower extremities.
None of these symptoms automatically mean serious kidney disease, but any of them, especially if they persist, should prompt blood and urine testing. If those tests come back abnormal, a nephrology referral is the logical next step.
Electrolyte Problems Linked to Kidney Function
Your kidneys regulate potassium, sodium, calcium, and phosphorus levels in your blood. When kidney function declines, potassium in particular can build up to dangerous levels. In people with kidney disease, a potassium level at or above 5.0 mmol/L is considered abnormal and requires monitoring and intervention. Levels between 5.1 and 5.9 are classified as mild hyperkalemia, 6.0 to 6.9 as moderate, and anything at 7.0 or above as severe.
If your potassium is persistently elevated, your primary care doctor may need to adjust medications, but a nephrologist is better equipped to manage the underlying kidney problem causing the imbalance. Potassium above 6.0 often requires closer monitoring, and levels above 6.5 can affect heart rhythm, sometimes requiring hospital-level care.
Family History of Kidney Disease
Polycystic kidney disease (PKD) is one of the most common inherited kidney conditions, affecting roughly 1 in 400 to 1,000 people. If a parent or sibling has PKD, you may want screening even without symptoms. Genetic testing isn’t recommended for everyone, but it’s particularly useful if your imaging results are inconclusive, if you’re considering donating a kidney, or if you’re under 30 with a family history of PKD and a negative ultrasound and you’re planning to start a family.
Beyond PKD, other hereditary conditions like Alport syndrome or certain types of glomerulonephritis can run in families. If multiple relatives have had kidney disease, kidney failure, or needed dialysis, bringing this up with your doctor and asking about nephrology screening is reasonable.
What to Expect at Your First Visit
A first nephrology appointment is primarily diagnostic. The nephrologist will review your existing lab work and likely order additional tests if they haven’t already been done. Expect a blood test measuring creatinine to calculate your eGFR, along with a urine test checking your albumin-to-creatinine ratio. A urine dipstick test may be done in the office to quickly screen for protein or blood.
Depending on your situation, the nephrologist may order imaging such as a kidney ultrasound to check for structural problems like cysts, obstructions, or unusual kidney size. In some cases, a kidney biopsy is needed to determine the exact type of kidney disease, though this isn’t routine for a first visit.
The appointment will also involve a thorough review of your medications, since many common drugs (including certain pain relievers and blood pressure medications) can affect kidney function. Come prepared with a list of everything you take, including supplements. The nephrologist will typically work alongside your primary care doctor, managing the kidney-specific aspects of your care while your regular doctor continues handling everything else.