BUN, Creatinine, Glucose and the Kidney Ratio

📖 Terms in this lesson

BUN-to-creatinine ratio: A ratio above about 20 to 1 with a normal creatinine suggests dehydration rather than kidney damage.

Hemoglobin A1c: The average blood glucose over the past two to three months; 6.5% or higher diagnoses diabetes.

Chloride (Cl-): Normal about 98 to 106 mEq/L (some labs 96 to 106); it follows sodium, so it falls with vomiting and loop diuretics and rises with dehydration or large volumes of normal saline.

Bicarbonate (serum CO2): The venous bicarbonate on a chemistry panel, normally 22 to 26 mEq/L (some labs 23 to 29); low means metabolic acidosis such as DKA or diarrhea, high means metabolic alkalosis such as vomiting, and below 10 is critical.

Blood urea nitrogen (BUN): Normal 10 to 20 mg/dL; it rises with kidney dysfunction, dehydration, GI bleeding, high protein intake and steroids, so a high BUN with a normal creatinine usually means dehydration rather than kidney damage.

Serum creatinine: Normal about 0.6 to 1.2 mg/dL; it is the specific kidney marker because diet and hydration barely move it, and a doubling of the creatinine means the glomerular filtration rate has roughly halved.

Estimated GFR (eGFR): Normal 90 mL/min/1.73 m² or higher; below 60 for three months defines chronic kidney disease, below 30 is severe, and below 15 is kidney failure, when dialysis or transplant is planned.

Fasting blood glucose: Normal 70 to 99 mg/dL; 100 to 125 is prediabetes and 126 or higher on two occasions diagnoses diabetes, while a random glucose of 200 or more with symptoms also diagnoses it.

Hemoglobin A1c target in diabetes: For most adults with diabetes the treatment goal is an A1c under 7%, roughly an average glucose of 150 mg/dL; a less strict goal under 8% is used for frail or older clients at risk of hypoglycemia.

Phosphorus (PO4): Normal 2.5 to 4.5 mg/dL and inverse to calcium; it rises in kidney failure (binders, low-phosphorus diet) and falls with refeeding and malnutrition, and below about 1 mg/dL is critical.

Albumin: Normal 3.5 to 5 g/dL; low albumin causes edema and a falsely low total calcium and reflects liver synthesis, protein loss or inflammation, so it is not a reliable nutrition marker on its own.

Prealbumin: Normal about 15 to 36 mg/dL; with a half-life of two days it tracks recent protein intake faster than albumin, below about 10 to 11 suggests severe protein depletion, and inflammation also lowers it.

Total protein: Normal about 6 to 8 g/dL, the sum of albumin and globulins; low with malnutrition, liver disease and nephrotic protein loss, high with dehydration and some blood cancers such as multiple myeloma.