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Kidney Disease Symptoms: Early Signs, and the Blood and Urine Tests That Find It

Early kidney disease usually causes no symptoms. Here are the signs that appear as kidney function falls, who should get checked, and which blood and urine tests answer which question.

Published

October 11, 2026

Read time

9 min read

Medically reviewed by

Rhonda Collins, FNP-C

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The honest answer to “what are the early signs of kidney disease” is that there usually are none. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) states that most people in the early stages of chronic kidney disease (CKD) do not have symptoms, and that for many people the only way to know is to have their kidneys checked with blood and urine tests ^[1]. The National Kidney Foundation (NKF) puts it more bluntly: only about 10% of people with CKD know they have it ^[2].

CKD is common. NIDDK estimates that more than 35 million US adults, more than 1 in 7, have it ^[1]. So the useful version of this article is a short list of the signs that can appear, followed by the part that actually finds kidney disease early: which tests to run, and what each one tells you.

Why early kidney disease is silent

Healthy kidneys have a large reserve. Filtering can fall well below normal before waste and fluid build up enough to cause anything you can feel. NIDDK notes that symptoms tend to appear as CKD becomes more advanced ^[1], and NKF notes that many people do not experience symptoms until the very late stages, or until large amounts of protein are leaking into the urine ^[2].

Kidney damage, though, can show up on a test long before it shows up as a symptom. MedlinePlus notes that a urinalysis can show protein or other changes months to years before symptoms appear ^[3]. That gap between what a lab test can see and what you can feel is the reason to test rather than wait.

Signs and symptoms of kidney problems

When symptoms do appear, most are non-specific. Each one on its own has far more common causes than kidney disease. NIDDK lists these signs of more advanced CKD ^[1]:

• tiredness or trouble sleeping;
• loss of appetite, nausea, or vomiting;
• trouble concentrating;
• a change in how often you urinate;
• foamy urine;
• itching, numbness, dry skin, or darkened skin;
• unintended weight loss;
• muscle cramps;
• chest pain or shortness of breath;
• swelling (edema) that gets worse over time.

NKF adds a few that are worth knowing because they point more specifically at the kidneys ^[2]:

• Foamy urine that takes several flushes to clear, which can mean protein in the urine.
• Persistent puffiness around the eyes, which can also reflect protein leaking into the urine.
• Swollen ankles and feet from sodium and fluid retention. Heart, liver, and leg vein problems cause swelling too.
• Blood in the urine, which can also come from kidney stones, infection, or a tumor.
• Needing to urinate more often, especially at night, which also has common non-kidney causes such as a urinary infection or an enlarged prostate.

None of these symptoms tells you whether your kidneys are the cause. A blood and urine test does.

When symptoms need urgent care, not a lab order

A sudden loss of kidney function is different from slowly developing CKD. MedlinePlus lists the signs of acute kidney failure, including little or no urine, new swelling of the legs, ankles, and feet, changes in mental status or mood, nausea or vomiting, and shortness of breath, and advises contacting a provider if urine output slows or stops ^[4].

Get medical care the same day, or emergency care if symptoms are severe, if you notice:

• much less urine than usual, or none, especially during an illness, dehydration, or after starting a new medicine;
• chest pain or severe shortness of breath;
• new confusion or unusual drowsiness;
• rapidly worsening swelling of the legs, face, or around the eyes.

These are not reasons to order a test online and wait for the results.

Who should get tested

You do not need symptoms to justify a kidney test. Because early CKD is silent, testing is aimed at people with risk factors. NIDDK names four main ones ^[1][5]:

• diabetes;
• high blood pressure;
• heart and blood vessel disease;
• a family history of kidney failure.

Risk also rises with age and with how long you have had diabetes, high blood pressure, or heart disease ^[1]. NIDDK notes that African American, Hispanic, American Indian, Native Hawaiian, and other Pacific Islander people are more likely to develop advanced kidney disease ^[1]. NIDDK recommends a kidney check every year for people with diabetes, and asking your provider how often to test if you have high blood pressure, heart disease, or a family history of kidney failure ^[5].

The KDIGO 2024 guideline, the international standard for CKD care, recommends testing people at risk with both a blood test for filtration and a urine test for albumin ^[6]. That pairing is the core of the next section.

Which test answers which question

Kidney disease is defined by two kinds of evidence. KDIGO defines CKD as abnormal kidney structure or function present for more than 3 months, most often shown by an estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73m², or by kidney damage such as albumin in the urine ^[6]. CKD is then staged by both measures together: a G category for filtration and an A category for albumin ^[6]. One test cannot answer both questions.

eGFR: how well the kidneys filter

eGFR is calculated from blood creatinine, a waste product of muscle, along with age and sex ^[6][7]. NIDDK describes a GFR of 60 or more as in the normal range, less than 60 as a possible sign of kidney disease, and 15 or less as kidney failure ^[5]. Since 2021, the NKF and the American Society of Nephrology have recommended the race-free CKD-EPI 2021 equation in the US ^[7][8].

eGFR can be normal while the kidneys are already damaged. That is why it is paired with a urine test. If you already have a low result, the low eGFR symptoms and causes guide walks through the stages, the temporary causes of a falsely low number, and when to retest. The eGFR biomarker overview explains the marker itself.

UACR: the earliest sign of damage

The urine albumin-to-creatinine ratio measures albumin, a protein that healthy kidneys keep out of the urine. A damaged kidney lets some albumin through ^[5]. NIDDK treats a UACR of 30 mg/g or less as normal and more than 30 mg/g as a possible sign of kidney disease ^[5]. KDIGO grades albuminuria as A1 (below 30 mg/g), A2 (30 to 300 mg/g), and A3 (above 300 mg/g) ^[6]. Albumin in the urine can show kidney damage while eGFR still looks normal ^[6]. A single high result is usually repeated to confirm it ^[5].

The UACR biomarker overview covers the marker, and our guide to the urine albumin-to-creatinine ratio goes deeper on what drives it.

Cystatin C: a check when creatinine may mislead

Creatinine depends on muscle mass, diet, and some medicines, not just kidney filtration. A very muscular person, someone who ate a large meat meal before the draw, or someone taking creatine supplements can have a creatinine-based eGFR that reads lower than their true filtration ^[6]. KDIGO recommends adding cystatin C when the creatinine estimate is likely to be less accurate and the result matters, for example to confirm a CKD diagnosis ^[6]. Equations that combine creatinine and cystatin C were more accurate than either marker alone in the CKD-EPI 2021 study ^[8].

Cystatin C is a separate blood test. The cystatin C overview explains the marker, our cystatin C article covers how it is used, and the cystatin C test cost guide compares pricing.

BUN: useful context, not a staging test

Blood urea nitrogen (BUN) measures urea, a waste product of protein breakdown ^[9]. It rises with reduced kidney function, but also with dehydration, a high-protein diet, burns, some medicines, and a recent heart attack, and it falls with low protein intake and liver disease ^[9]. That makes BUN, and the BUN-to-creatinine ratio, more useful for context such as hydration than for deciding whether someone has CKD. KDIGO stages CKD with eGFR and urine albumin, not BUN ^[6]. BUN appears on a standard metabolic panel and as a separate blood urea nitrogen test.

Reading results without self-diagnosing

A single abnormal result is a reason to check again, not a diagnosis. CKD requires an abnormality that lasts more than 3 months ^[6], and dehydration, an acute illness, intense exercise, or a large meat meal can move a single creatinine or urine albumin result ^[6]. A useful sequence is to repeat the abnormal test, add the measure you did not run (urine albumin if you only had eGFR, or the reverse), and add cystatin C when creatinine may be misleading.

KDIGO recommends referral to a kidney specialist when eGFR is below 30, when urine albumin is persistently 300 mg/g or higher, or when eGFR falls quickly ^[6]. Results like these are worth discussing with your doctor promptly.

Where to start

If you have diabetes, high blood pressure, heart disease, or a family history of kidney failure, or you have simply never had your kidneys checked, start with the two measures KDIGO uses to find and stage CKD. The Mito Kidney Panel runs both from one visit: a blood creatinine with creatinine-based eGFR, and a random urine sample for the albumin-to-creatinine ratio. It does not include BUN or cystatin C, which are separate tests you can add when the question calls for them.

Panel contents and prices differ more than the names suggest, so the kidney function test cost guide explains how to compare options.

References

1. NIDDK: What is chronic kidney disease?
2. National Kidney Foundation: 10 signs you may have kidney disease
3. MedlinePlus: Chronic kidney disease
4. MedlinePlus: Acute kidney failure
5. NIDDK: Chronic kidney disease tests and diagnosis
6. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int. 2024
7. National Kidney Foundation: Estimated glomerular filtration rate (eGFR)
8. Inker LA, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021
9. MedlinePlus: BUN (blood urea nitrogen) test

Related Resources

• Low eGFR: symptoms, causes, and what the result means
• eGFR (creatinine) biomarker overview
• UACR biomarker overview
• Cystatin C biomarker overview
• High creatinine symptoms
• High BUN symptoms
• Kidney function test cost guide