Kidney disease is found and followed with simple blood and urine tests. Knowing what your numbers mean helps you take an active part in your care. Ask for copies of your results and bring them to your visits.
Blood tests
eGFR (estimated glomerular filtration rate)
eGFR estimates how well your kidneys filter waste. It is calculated from your creatinine level, age, and sex. An eGFR of 60 or higher is in the normal range for most adults. An eGFR below 60 for three months or more is a sign of chronic kidney disease, and the number is used to stage CKD.
Creatinine
Creatinine is a waste product from normal muscle activity. Healthy kidneys remove it from the blood. When kidney function falls, creatinine rises. Muscle mass, diet, and some medicines can affect the result.
Cystatin C
Cystatin C is another blood marker of kidney function. It is less affected by muscle mass, so it is sometimes used with creatinine to get a more accurate eGFR.
BUN (blood urea nitrogen)
BUN measures urea, a waste product from protein. It can be high when the kidneys are not working well, but it is also affected by dehydration, a high-protein diet, and some medicines.
Electrolytes and minerals
As CKD progresses, your doctor may check potassium, sodium, bicarbonate (acid balance), calcium, phosphorus, parathyroid hormone (PTH), and vitamin D. These help guide your diet and medicines.
Hemoglobin
The kidneys make a hormone that helps produce red blood cells. People with CKD can develop anemia (a low red blood cell count), which can cause tiredness and shortness of breath.
Urine tests
Urine albumin-to-creatinine ratio (UACR)
UACR measures albumin, a protein, in your urine. Healthy kidneys keep albumin in the blood. A UACR below 30 mg/g is normal. A result of 30 mg/g or higher on repeated tests is a sign of kidney damage, and higher levels mean a greater risk that kidney disease will progress.
Urinalysis
A urinalysis looks for protein, blood, sugar, signs of infection, and other clues about the health of the kidneys and urinary tract.
Imaging and other tests
A kidney ultrasound shows the size and shape of the kidneys and can find cysts, stones, or blockages. In some cases a kidney biopsy, where a tiny sample of kidney tissue is examined, is needed to find the exact cause of kidney disease.
Tips for understanding your results
- Look at the trend. One result can change with illness, dehydration, or a new medicine. Several results over time tell the real story.
- Know both numbers. eGFR and urine albumin together give the clearest picture of your kidney health.
- Ask before you fast or change medicines for a lab test.
Questions to ask at your visit
- What are my eGFR and UACR, and how have they changed since my last test?
- Are any of my electrolytes or minerals out of range?
- Do I need any changes to my diet or medicines based on these results?
- When should I repeat these tests?
This guide is general education and is not a substitute for medical advice. Talk with Dr. Salim or your care team about your own situation. Informed by patient materials from the National Kidney Foundation; learn more at kidney.org.