March 22, 2001
Blood Tests and Insulin Injections
Question from New York, USA:
I had a high two-hour after dinner blood sugar (135 mg/dl [7.5 mmol/L]), so I tested an hour later and it was 113 mg/dl [6.3 mmol/L]. At bedtime and it was 90 mg/dl [5 mmol/L], and, since I often have a problem with ketones, I ate a bedtime snack and drank some V-8 juice throughout the night trying to avoid morning ketones. I woke up at 5:00 am to test, and my blood sugar was 100 mg/dl [5.6 mmol/L]! Does that mean I could have high blood sugar lingering at night? I tested this morning and my fasting was still a little high, at 92 mg/dl [5.1 mmol/L]. I’m very puzzled as to how I should determine whether I need a bedtime snack at all.
I know what the cutoffs are for the fasting and one- and two-hour after meal blood sugars, but what should the blood sugar be at bedtime?
Answer:
Sounds like you did great. Blood sugars before bed should not be high, but they should not be low, either. Most people I know don’t want the bedtime sugar less than 90-100 mg/dl [5-5.6 mmol/L]. The purpose of the snack is to prevent low blood sugars. The lows in the night are particularly serious because you can’t defend yourself from them. Some physicians ask their patients to check sugars intermittently at 3:00 am with the goal of keeping the sugars above 80-90 mg/dl [4.4-5 mmol/L]. Sounds like your sugars did not do badly over the night. I anticipate what happened was that the sugar went up a little after the snack and settled back down where you found it. Good job.
JTL
