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Lab Values Explained

Measures of Kidney Function

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Serum Creatinine Creatinine is a waste product that is made when your body breaks down protein you eat and when muscles are injured. A high serum (blood) creatinine level means kidney damage. Creatinine levels may vary somewhat, even when the kidneys work normally. So, your doctor should check your level more than once before diagnosing CKD. Creatinine levels tend to be higher in men and people with large muscles. Measuring creatinine is only the first step to finding your level of kidney function. The normal serum creatinine range for men is 0.5-1.5 mg/dL. The normal range for women is 0.6-1.2 mg/dL.
Creatinine Clearance Creatinine clearance is a test sometimes used to estimate filtering capacity of the kidneys. The amount of creatinine in your urine is compared to the amount of creatinine in your blood. Your doctor may test your urine by asking you to collect your urine for 24 hours in a special container. Normal creatinine clearance for healthy men is 97-137 mL/min. Normal creatinine clearance for healthy women is 88-128 mL/min.
Glomerular Filtration Rate (GFR) GFR is a more accurate way to measure how well your kidneys filter wastes from your blood. Your GFR gives your doctor an idea of the speed at which your kidneys are failing, and whether you are at risk for complications of kidney disease. GFR can be estimated from serum creatinine, using a formula. Healthy adults have a GFR of about 140*; normal is greater than 90. Children and the elderly usually have lower GFR levels. A GFR less than 15 is kidney failure.

*GFR is reported in mL/min/1.73 m2.
Urine Albumin Inside healthy kidneys, tiny filtering units called nephrons filter out wastes but keep in large molecules, like red blood cells and albumin (protein). Some kidney diseases damage these filters so albumin and other proteins can leak into the urine. Protein—albumin—in the urine can be a sign of kidney disease. Albumin can be measured with a urine dipstick or a 24-hour urine collection to find out how much protein is "spilling" into the urine. Albumin levels can increase with heavy exercise, poor blood sugar control, urinary tract infections, and other illnesses. In a 24-hour urine sample, a normal level is less than 30 mg/day.
Microalbuminuria Microscopic amounts of protein too small to be measured with a standard dipstick test can be an early sign of kidney disease—especially in people with diabetes. Special dipsticks or laboratory tests can find microalbuminuria. The American Diabetes Association guidelines recommend that anyone with type 1 or type 2 diabetes have a test for microalbuminuria at least yearly. Urine in healthy people contains from 30mg/L to 300mg/L of albumin.
Blood Urea Nitrogen (BUN) Blood Urea Nitrogen (BUN) is another measure of wastes (urea) in the blood. Urea is produced from the breakdown of protein already in the body and protein in your diet. A high BUN usually means that kidney function is less than normal, but other factors may affect the BUN level. Bleeding in the intestines, congestive heart failure, and certain medications may make the BUN higher than normal. As BUN rises, symptoms of kidney disease may appear, such as a bad taste in the mouth, poor appetite, nausea, and vomiting. In dialysis, BUN is used to measure whether a person is receiving the correct amount of dialysis. Sometimes a low BUN may also mean that you are not eating enough protein. The normal BUN level for healthy individuals is 7-20 mg/dL in adults, and 5-18 mg/dL in children.

Patients on dialysis have higher BUN levels, usually 40-60 mg/dL. The nephrologist (kidney doctor) and dietitian will help determine whether the BUN is in the correct range.

Measures of Anemia

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Hematocrit (Hct) Hematocrit is the percentage of red blood cells in the blood, used to check for anemia. Anemia—a shortage of oxygen-carrying red blood cells—often begins at the early stages of kidney disease. It causes severe fatigue, heart damage, and other health problems. Anemia can be treated. The normal Hct level for healthy individuals is 40-50% for men and 36-44% for women.
Hemoglobin (Hgb) Hemoglobin is the part of red blood cells that actually carries oxygen. Both hematocrit and hemoglobin levels are measured to check for anemia. The normal Hgb level for healthy individuals is 14 to 18 g/dL for men and 12 to 16 g/dL for women.

Measures of Diabetes Control

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Hemoglobin A1c (HbA1c) The HbA1c measures your blood sugar control over the last 3 months. According to the National Diabetes Education Program, people with diabetes should have their HbA1c tested at least once every 6 months. The goal is to keep your HbA1c less than 6.5%.
Glucose Glucose is blood sugar. It is measured to determine if your body is able to digest and use sugar and carbohydrates correctly. Although high blood glucose levels are mainly found in diabetics, some medications can raise your blood glucose level. Diabetes is diagnosed if the non-fasting blood glucose is higher than 200 mg/dL. Normal (fasting) glucose levels are 65-110 mg/dL. In people with diabetes, the blood glucose goal before eating is 80-120 mg/dL. After eating, the blood glucose goal is 100-140 mg/dL.

Measures of Nutrition

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Serum Albumin The level of albumin (protein) in the blood is a measure of good nutrition. Research shows that people with kidney disease who become malnourished and do not get enough protein may suffer from many complications. It is especially important for people on low protein diets to have their serum protein levels measured. Normal serum albumin levels in healthy people are 3.6-5.0 g/dL. The goal for people on dialysis is an albumin level greater than 4.0 g/dL.

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