Which statement correctly contrasts glycosylated hemoglobin (GHb) with serum glucose for monitoring diabetes?

Which statement correctly contrasts glycosylated hemoglobin (GHb) with serum glucose for monitoring diabetes?

• A. GHb reflects long-term average; serum glucose reflects long-term
• B. GHb reflects short-term; serum glucose reflects long-term
• C. GHb reflects long-term average; serum glucose reflects short-term variations
• D. GHb and serum glucose both reflect only short-term changes

Answer: (C)

Glycosylated hemoglobin (HbA1c) provides a record of how high blood glucose has been over a longer period, because glucose gradually attaches to hemoglobin in red blood cells, and those cells live about 120 days. This makes HbA1c a measure of average glucose over roughly 2–3 months. Serum (plasma) glucose, on the other hand, is a real-time snapshot that can change rapidly with meals, activity, stress, and fasting. A single value captures current levels and short-term fluctuations, not long-term control. So the statement that GHb reflects a long-term average and serum glucose reflects short-term variations accurately contrasts the two. The other options would misstate the time frame for one or both measures.

Glycosylated hemoglobin (HbA1c) provides a record of how high blood glucose has been over a longer period, because glucose gradually attaches to hemoglobin in red blood cells, and those cells live about 120 days. This makes HbA1c a measure of average glucose over roughly 2–3 months. Serum (plasma) glucose, on the other hand, is a real-time snapshot that can change rapidly with meals, activity, stress, and fasting. A single value captures current levels and short-term fluctuations, not long-term control. So the statement that GHb reflects a long-term average and serum glucose reflects short-term variations accurately contrasts the two. The other options would misstate the time frame for one or both measures.