Which two laboratory values reflect kidney function and are relevant to dosing adjustments?

• A. Hemoglobin and hematocrit
• B. Serum potassium and bicarbonate
• C. LDL cholesterol and HDL
• D. Serum creatinine and estimated glomerular filtration rate (eGFR)

Answer: (D)

The main idea is that dosing changes for many drugs depend on how well the kidneys can clear them. Serum creatinine is a waste product filtered by the kidneys; higher levels suggest reduced filtration. The estimated glomerular filtration rate, or eGFR, uses creatinine along with factors like age and sex to estimate how much the kidneys are filtering per minute. Together, these values quantify kidney function and show whether dose adjustments or longer dosing intervals are needed to avoid drug accumulation and toxicity.

The other values aren’t direct measures of kidney filtering ability. Hemoglobin and hematocrit reflect blood oxygen-carrying capacity and not how well the kidneys are filtering. Potassium and bicarbonate indicate electrolyte and acid-base status, which the kidneys help regulate, but they don’t provide a precise assessment of renal clearance capacity for dosing. LDL and HDL are lipid markers, unrelated to kidney function.