By Timothy Bailey, MD, FACE, FACP

You can do some sophisticated analysis of your blood glucose trends using the diabetes software that is linked to your meter. With a weekly or monthly chart that shows your blood glucose patterns, your doctor can review your overall trends and spot blood glucose issues at specific times of day. This type of analysis is called pattern management. It helps your doctor fine-tune your insulin regimen so that you can stay within range more of the time.

Software Matches Your Testing Routine

The first step in using diabetes software is to tell the program about your testing routine. This allows the software to label the blood glucose readings as either “before eating” or “after eating”. These are often split into eight “time buckets”, shown in Figure 1:

• Pre (before)-Breakfast (before you eat breakfast)
• Post (after)-Breakfast (after breakfast, but not too close to lunch)
• Pre-Lunch (just before lunch)
• Post-Lunch (after lunch, but not too close to dinner)
• Pre-Dinner (just before dinner)
• Post-Dinner (after dinner, but not too close to bedtime)
• Bedtime
• Night (ideally about half-way between bedtime and waking up)

Figure 1. Example of time periods

Using the times in Figure 1 as an example, if you test your blood glucose between the Pre-Breakfast time of 6 am and the Post-Breakfast time of 8 am, then it is classified as a “Pre-Breakfast”. It is a new concept for most people, but well worth understanding, because of the powerful features (such as time-specific averaging) that this makes possible.

Some people stick to a consistent routine at home and work, but others have unpredictable schedules. Someone doing shift work, for example, may work nights one week, evenings another week, then work during the day at other times. If your mealtime routine changes often, you can still use the software time buckets. You just can't associate those times with a particular type of meal such as breakfast or lunch.

Look for Patterns of High and Low Readings

Once you have things set up, the software makes the hard stuff automatic. Look at the chart in figure 2. This chart calculates the average reading for each of your mealtimes over the past several weeks. The green band represents the target blood glucose range of 90 to 130 mg/dL. The yellow band shows blood glucose levels that are too high, and the red band shows readings that are too low.

In this example, the average blood glucose levels are low “Pre-Lunch”, and too high at Bedtime. Each oval shows the average blood glucose reading for that time of day.

Figure 2. Example of blood Glucose and Insulin chart

• The low “Pre-Lunch” average means that too much insulin is being injected at breakfast in relation to the amount of carbohydrate that is being eaten.
  
• The high "Bedtime" average may mean that too little insulin is being taken at dinner in relation to the carbs that are eaten. Or, too many high-carb snacks are being eaten while watching TV during the evening.

Notice the dark purple line (I) above and below '204' at bedtime. This bar shows the variability in the blood glucose readings at that time. This is called the "standard deviation".

• The shorter this purple line is, the more consistent the readings are at that time of day. This makes it more likely that an insulin dose change will have the effect your doctor is looking for.
  
  
• If the whole line is very long, it means that the readings at that time of day vary a great deal. You'll need to figure out how your routine varies during the evening, then try to be more consistent so that you can get the bedtime readings into a much narrower range - reducing the deviation. Possible reasons for wide-ranging high blood sugars at bedtime may include:
  
  
• Too little insulin at dinner
  
  
• Different snacks eaten on different evenings - some higher carb than others
  
  
• Sometimes you exercise during the evening, sometimes you don't

Are you more a numbers person? If so, a blood glucose summary is for you (Figure 3). In this chart, you look at your data in a table. The rows represent the “time buckets”. The columns give:

• The total number of readings in that “time bucket”
  
  
• Average number of tests per day
  
  
• Average (mean) blood glucose level at each time of day
  
  
• Standard deviation, which shows how much your readings vary at each time of day
  
  
• The lowest and highest reading recorded at each time of day
  
  
• The number and % of readings that were below target, in range, and above target

Figure 3. Example of summary chart

Trend Line and Moving Average Over Time

To see how your average blood glucose is trending over time, just turn on the moving average feature in your software. In Figure 4, the moving average is the white line. You can also look at individual readings on each day.

In our example, the Bedtime blood sugars are generally too high, and they are also highly variable. If we look back at specific dates such as May 26 when the bedtime reading was over 250, we can figure out what we did or ate during that evening to produce such a high level.

Figure 4. Example of trend chart

In short, diabetes software gives you many ways to help you understand and better manage your diabetes. It's worthwhile spending some time to add this important tool to your diabetes care kit.

You can gain even greater insight into your diabetes routine and how to improve it.

Dr. Bailey is Board-Certified in Endocrinology, Metabolism, and Internal Medicine. He specializes in treating diabetes, osteoporosis, thyroid diseases, and lipid disorders at North County Endocrine. He is in full-time clinical practice and a clinical investigator active in conducting phase II to IV clinical trials. Optimally managing data from medical devices has been is a long-term interest of his. As a clinical Assistant Professor at the University of California at San Diego, he is active in the education of endocrinology fellows. He is a frequent speaker to both physician and patient groups.

Important note: The content of this article is not intended to be a substitute for professional medical advice, diagnosis or treatment. Do not disregard your doctor's advice or delay in seeking it because of something you have read on this article.