What is a kidney function test?

A kidney function test is a procedure that measures how well your kidneys are functioning. The test involves getting a sample of blood from a vein in your arm or hand, then sending the sample to a lab for analysis.

Kidney function testing is important for individuals who are at risk of kidney disease or who are experiencing symptoms of kidney problems. Some of the risk factors for kidney disease according to the Mayo Clinic include:

• High blood pressure
• Diabetes
• Family history of kidney disease
• Smoking
• Obesity
• Age over 60

What’s measured by a kidney function test?

A kidney function test measures several biomarkers that provide information about how well your kidneys are functioning. Some of the common biomarkers, according to the CDC included:

• Creatinine - a waste product produced by muscles that are filtered out of the blood by the kidneys
• Blood Urea Nitrogen (BUN) - the amount of urea nitrogen in the blood that is filtered out by the kidneys. High levels of BUN can be a sign of kidney problems, according to the Mayo Clinic
• Estimated Glomerular Filtration Rate (eGFR) - an estimate of how well the kidneys are filtering waste products from the blood
• Urinalysis - a way to find protein or blood in the urine, that may indicate kidney problems
• Electrolyte levels - minerals, such as sodium, potassium, and chloride, that are essential for many bodily functions
• Albumin - a protein that is important for maintaining fluid balance in the body.

Your doctor may order one or more of these tests depending on your individual situation and medical history. The results of the tests can help your doctor diagnose kidney disease, monitor the progression of the disease, and develop an appropriate treatment plan, according to the National Kidney Foundation.

How is a kidney function test performed?

Kidney function tests involve giving a sample of blood. For this process, a healthcare provider will use a small needle to gain access to a vein in your arm or hand. They will draw a small sample of blood, which will then be sent to a lab for analysis.

When should I get a kidney function test?

According to the National Kidney Foundation and the Mayo Clinic, you should consider getting kidney function tests if you have any risk factors for kidney disease. The risk factors include:

• High blood pressure
• Diabetes
• Family history of kidney disease
• Obesity
• Age over 60
• Smoker
• Heart disease
• Peripheral artery disease
• Lupus or other autoimmune disorder

Additionally, you should consider kidney function tests if you use any medication that can possibly cause kidney damage. These medications, according to the National Kidney Foundation, include, but are not limited to:

• Aspirin
• Naproxen
• Ibuprofen

Your healthcare provider may recommend kidney function tests as part of your routine health and wellness testing, according to the CDC.

What are the symptoms of kidney problems

In its early stages, kidney disease or kidney damage may not present with any symptoms, according to the Mayo Clinic. As the damage or disease process progresses, you may experience the following symptoms:

• Swelling in the hands, feet, or ankles
• Fatigue or weakness
• Difficulty sleeping
• Poor appetite
• Nausea or vomiting
• Changes in urine output or color
• Blood in the urine
• Pain or difficulty urinating

Understanding your kidney function test results

Understanding your kidney function test results can help you and your doctor assess your kidney health and make informed decisions about your treatment plan. Here are some of the common biomarkers included in a kidney function test and what the results may indicate, according to the National Kidney Foundation:

• Creatinine: Higher levels of creatinine may indicate decreased kidney function.
• Blood Urea Nitrogen (BUN): Higher BUN levels may indicate kidney problems, dehydration, or other conditions.
• Estimated Glomerular Filtration Rate (eGFR): eGFR is a measure of how well your kidneys are filtering waste products from the blood. An eGFR that is lower than normal may indicate kidney problems.
• Urinalysis: A urinalysis can detect abnormalities, which may indicate kidney problems or other conditions like diabetes.
• Electrolyte levels: Abnormal levels of electrolytes in the blood can be a sign of kidney problems or other conditions like dehydration or malnutrition.

It's important to note that a kidney function test is just one tool that doctors use to assess kidney health. Your doctor will also consider other factors, such as your medical history, symptoms, and physical exam results, when interpreting your test results.

If your test results indicate kidney problems, your doctor may recommend further testing or refer you to a kidney specialist for further evaluation and treatment.

What is the normal range for kidney function test results?

The normal range for kidney function test results can vary depending on the specific test being performed and the laboratory that is analyzing the results. Here are some general guidelines for the normal ranges of the most common measures in a kidney function test, according to the CDC:

• Creatinine: 0.6 to 1.3 mg/dL for adult men and 0.5 to 1.1 mg/dL for adult women
• Blood Urea Nitrogen (BUN): 6 to 20 mg/dL
• Estimated Glomerular Filtration Rate (eGFR): An eGFR of 60 or higher is generally considered normal
• Urinalysis: A urinalysis may be considered normal if there are no abnormalities—such as protein, blood, or glucose, detected in the urine.
• Electrolyte levels - The normal range for electrolyte levels in the blood can vary depending on the specific electrolyte being measured.

It's important to note that the normal ranges for these measures can vary depending on factors such as age, gender, and other individual factors, according to the Mayo Clinic. Additionally, a single abnormal test result does not necessarily indicate kidney disease or other kidney problems.

Your doctor will consider your test results in the context of your medical history, physical exam, and other factors to determine whether further testing or treatment is necessary.

What are the reasons for abnormal kidney function test results?

There are several reasons why a kidney function test may show abnormal results. Here are some of the common causes of abnormal kidney function test results, as outlined by the National Kidney Foundation:

• Kidney disease
• Dehydration
• Certain medications (such as nonsteroidal anti-inflammatory drugs, also known as NSAIDs)
• Urinary tract obstruction
• Infection
• Autoimmune disorders (such as lupus or vasculitis)
• Diabetes
• High blood pressure
• Genetic conditions

Finding a kidney function test

You can find and request a kidney function test at most healthcare facilities, including:

• Walk-in clinics
• Urgent care clinics
• Primary care clinics
• Hospitals
• Walk-in laboratory

Can I get an at-home kidney function test?

There are at-home tests available for testing your kidney function, however, it is important to note that these tests may be less accurate than medical-grade testing.

The National Kidney Foundation recommends that you should consult a medical provider if:

• You are experiencing symptoms of kidney disease
• You are at higher risk of getting kidney disease
• You are worried that you may have kidney damage

Cost of kidney function tests

The cost of kidney function testing will vary depending on your location, your testing facility, and your insurance coverage. The national average of kidney function tests in the United States is between $20 and $34.

How is kidney disease diagnosed?

A medical provider can diagnose kidney disease with a combination of diagnostic testing, a physical exam, and an understanding of past and present medical history, according to the Mayo Clinic.

What are the symptoms of kidney disease?

The symptoms of kidney disease usually develop over time, as kidney damage slowly progresses and causes a build-up of fluid or body waste, according to the Mayo Clinic. The Mayo Clinic lists the symptoms of kidney disease as the following:

• Nausea
• Vomiting
• Loss of appetite
• Fatigue and weakness
• Sleep problems
• Urinating more or less
• Decreased mental sharpness
• Muscle cramps
• Swelling of feet and ankles
• Dry, itchy skin
• High blood pressure (hypertension) that's difficult to control
• Shortness of breath
• Chest pain

What are the risk factors for kidney disease?

There are several factors that can raise your risk of developing kidney disease, according to the Mayo Clinic. Some of these factors include:

• Diabetes
• High blood pressure
• Heart disease
• Smoking
• Obesity
• Family history of kidney disease
• Abnormal kidney structure
• Age > 60
• Frequent use of medications that can damage the kidneys (such as NSAIDs)