Last reviewed: January 10, 2026
Originally published: January 10, 2026
Last reviewed: January 10, 2026
Originally published: January 10, 2026
Comprehensive guide to understanding kidney function through blood tests. Learn about creatinine, eGFR, electrolytes, and other essential markers for assessing kidney health.
Your kidneys are vital organs that filter waste products from your blood, regulate fluid balance, maintain electrolyte levels, and produce hormones that control blood pressure and red blood cell production.
Kidney function blood tests measure how well your kidneys are performing these essential functions. Regular monitoring is crucial for early detection of kidney disease, which often shows no symptoms until significant damage has occurred.
This guide covers the 8 key blood tests used to assess kidney function and health.
Explore different kidney function tests to understand what each test measures and why it's important for your kidney health.
Blood Urea Nitrogen test to measure waste product from protein breakdown
Measures creatinine levels to assess kidney filtration function
Estimated Glomerular Filtration Rate to measure kidney filtering capacity
Measures sodium levels to assess electrolyte balance and kidney regulation
Measures potassium levels regulated by kidney function
Measures calcium levels that kidneys help regulate
Measures phosphorus levels controlled by kidney function
Detailed information about each kidney function blood test, including what it measures, and clinical significance.
Measures waste product from muscle metabolism
Creatinine is a waste product produced by muscles from the breakdown of creatine. Healthy kidneys filter creatinine from the blood into urine. High levels indicate impaired kidney function.
Estimates kidney filtration rate
eGFR estimates how much blood passes through the glomeruli (kidney filters) each minute. It's calculated using creatinine level, age, sex, and sometimes race. Lower values indicate reduced kidney function.
Measures nitrogen in blood from urea
BUN measures the amount of nitrogen in your blood that comes from urea, a waste product of protein metabolism. Kidneys filter urea from blood. High BUN can indicate kidney problems or dehydration.
Quick reference table comparing all kidney function blood tests at a glance.
| Test Name | Abbreviation | Purpose | Sample Type |
|---|---|---|---|
| Creatinine | Cr | Measures waste from muscle metabolism | Blood Serum |
| Estimated GFR | eGFR | Estimates kidney filtration rate | Calculated |
| Blood Urea Nitrogen | BUN | Measures nitrogen from urea waste | Blood Serum |
| Sodium | Na⁺ | Electrolyte balance, fluid regulation | Blood Serum |
| Potassium | K⁺ | Muscle/nerve function, heart rhythm | Blood Serum |
| Calcium | Ca⁺⁺ | Bone health, muscle function | Blood Serum |
| Phosphorus | PO₄ | Bone formation, energy production | Blood Serum |
Simple ways to support and maintain healthy kidney function.
Drink plenty of water throughout the day to help kidneys clear sodium, urea, and toxins from the body. Aim for 6-8 glasses daily.
Consume a balanced diet rich in fruits, vegetables, and whole grains. Limit salt, processed foods, and excessive protein intake.
Maintain a healthy weight through regular physical activity. Obesity increases the risk of diabetes and high blood pressure, which can damage kidneys.
Limit use of non-steroidal anti-inflammatory drugs (like ibuprofen) which can harm kidneys when taken regularly or in high doses.
Some medications can affect kidney function. Always take medications as prescribed and discuss potential kidney effects with your doctor.
High blood pressure is a leading cause of kidney damage. Monitor and manage your blood pressure through lifestyle and medication if needed.
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