Q.96 When the blood glucose level of a healthy person is 100 mg/dL, which one of the
following options is most likely to represent the level of glucose in the urine of that
person?
(A) < 1 mg/dL
(B) 10 mg/dL
(C) 50 mg/dL
(D) 100 mg/dL
Blood glucose 100 mg/dL represents a normal fasting level in healthy individuals, where kidneys efficiently reabsorb nearly all filtered glucose, resulting in negligible urine glucose. This CSIR NET Life Sciences question tests understanding of renal glucose handling and the renal threshold for glucose reabsorption, typically around 180 mg/dL.
Renal Glucose Reabsorption Basics
Glucose filters freely at the glomerulus but gets almost completely reabsorbed in the proximal tubule via SGLT2 and SGLT1 transporters until the transport maximum (TmG) of about 350-375 mg/min is reached. At blood glucose 100 mg/dL—well below the renal threshold of 180 mg/dL—no significant glucose spills into urine, keeping levels trace or undetectable (<1-15 mg/dL). Healthy kidneys maintain this efficiency, preventing glycosuria unless plasma levels exceed the threshold.
Option Analysis
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(A) < 1 mg/dL: Correct. Normal urine glucose in healthy people is trace (0-15 mg/dL, often <1 mg/dL detectable), as 100% reabsorption occurs at 100 mg/dL blood glucose.
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(B) 10 mg/dL: Incorrect. While trace amounts (1-15 mg/dL) may appear due to minor detection limits, 10 mg/dL exceeds typical undetectable levels at normal blood glucose and suggests slight elevation.
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(C) 50 mg/dL: Incorrect. Levels above 25-30 mg/dL indicate pathologic glucosuria, impossible at 100 mg/dL blood glucose in healthy kidneys.
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(D) 100 mg/dL: Incorrect. Urine glucose equaling blood glucose (100 mg/dL) occurs only post-threshold saturation (~180+ mg/dL), causing significant glycosuria.
Clinical Relevance for CSIR NET
This question emphasizes the renal threshold concept: below 180 mg/dL, urine glucose remains <1 mg/dL in health; above it, excretion rises linearly. For exams, remember TmG variability (300-375 mg/min) and splay effect causing slight glycosuria before full threshold. Glycosuria at 100 mg/dL signals renal glycosuria (rare tubular defect).
