Question

As a healthy volunteer, you have just signed up for a study of blood glucose level [Glu]. You are to monitor your [Glu] every two hours during day and night. Draw a diagram which shows how [Glu] varies over a day-night cycle (0000-2400 hours. On the same diagram, indicate the timing of your meals. On a separate y-axis (but synchronous x-axis), indicate your expected plasma [insulin] and [glucagon]. Most diabetics rely on subcutaneous administration of insulin to control their plasma [Glu] levels. Why can’t they just ingest an insulin “pill” with their meal?

Answer 1

Under everyday life conditions, the mean 24-hour interstitial fluid glucose concentration was about 90 mg/dl and the mean fasting glucose concentration was about 80 mg/dl. The highest postprandial increase in interstitial glucose concentrations was observed after breakfast (peak 132.3 ± 16.7 mg/dl, range 101–168 mg/dl), and mean time to peak glucose was between 46 and 50 minutes. Previous studies investigating blood glucose concentrations in healthy subjects have demonstrated similar results for fasting glucose and postprandial peak glucose levels.

Breakfast: 7.30 AM

Lunch: 1.00 PM

Dinner: 7.30 PM

Time (hours)	Glucose (mg/dl)	Expected Insulin (pmol/L)
6	83	22
8	137	100
10	80	60
12	82	22
14	121	90
16	82	60
18	83	22
20	130	95
22	85	62
24	83	22
2	83	22
4	82	22
6	83	22

The above image shows the relationship between levels of glucose, insulin and glucagon.

The hormone insulin is made up of proteins and if it is taken by mouth it will be denatured by the digestive process. This   would inactivate the insulin. Therefore, when the body can’t make insulin, it can’t be taken in pill form and at this time must be injected subcutaneously.