Final answer:
The Glycemic Index does not provide accurate timing for glucose spikes or carbohydrate conversion to glucose. It gives a general comparison of post-meal blood glucose effects of different foods. Diabetes mellitus can be diagnosed by observing elevated blood glucose levels that do not normalize within normal time range after glucose ingestion or a meal.
Step-by-step explanation:
The Glycemic Index (GI) is a measurement that considers how quickly a carbohydrate-containing food can increase blood glucose levels, relative to pure glucose. However, it does not accurately indicate the timing of the spike in carbohydrate to glucose conversion nor correlate precisely with the exact moment of carbohydrate conversion to glucose. GI provides a rough comparison of different foods in terms of their post-ingestive glycemic effects, but it does not give precise timings for glucose spikes or when carbohydrate conversion begins.
Upon ingestion of glucose, a normal person will experience a rise in blood glucose levels which peaks around one hour and returns to baseline after approximately 2½ hours, thanks to insulin secretion. In contrast, a person with diabetes mellitus may experience a rapid and higher rise in blood glucose levels within half an hour, and their blood glucose levels may not return to normal even after 2½ hours. Insulin administration in normal individuals or insulin responsive diabetes patients would result in a different blood glucose profile, with a rapid decrease, followed by normalization over similar time frame as seen after glucose ingestion.
Assessing blood sugar after a meal can help diagnose diabetes. D-glucose, or blood sugar, should be in the range of 70 to 130 mg/dL before eating and below 140 mg/dL after eating in healthy individuals. Enzymatic methods offer precise blood glucose measurements, aiding in the diagnosis of diabetes or hypoglycemia.