for a list of available programs, or visit integrateddiabetes.com/diabetic-logsheets for a variety of downloadable and printable logging systems).
Blood sugar readings by themselves are not of much use unless they are all running above or below your desired range. For most of us, that just isn’t the case. When inconsistencies exist, you need to figure out why the readings are going up or down. Were they caused by too much or too little food? Miscounting the carbs? Incorrect insulin doses? Changes in physical activity? Stress or illness? The weather?
To figure out why your blood sugar levels vary, your records should include
• amounts of insulin taken (and other diabetes medications, if the doses vary)
• food consumed (grams of carbohydrate and anything else noteworthy, like restaurant meals or parties)
• physical activity (type and length of exercise as well as other labor-intensive activities such as housework, yard work, shopping, and extended walking)
• stress that might affect blood sugars (illness, menstrual cycles, emotional events, and hypoglycemic episodes)
• if you’re a pump user, when infusion set changes take place
In addition to logging apps, this type of information can be logged electronically as “events” in some CGM receivers, glucose meters, pumps, or apps that link with these devices. Use those features! When generating reports, the information that accompanies the glucose data can be extremely valuable for making wise adjustments.
C. Data Analysis
Reviewing and interpreting your self-monitoring records is essential. Otherwise, your logbooks and stored data are about as useful as those adorable but lonely characters on the Island of Misfit Toys in the old TV special Rudolph the Red-Nosed Reindeer .
For most people, it is best to review your own records on a weekly or every-other-week basis.
Keep track of how often your readings (or how much time, if you use a CGM) are above, below, and within your target range for each phase of the day, fasting, morning, afternoon, evening, and overnight.
At any phase of the day, if more than 25 percent of your glucose values are above your acceptable range, or more than 10 percent are below, changes to your diabetes management program are probably in order.
Because low blood sugars can sometimes produce high readings a few hours later, eliminating the lows before addressing the highs is usually the best course of action.
It is necessary to eliminate low blood sugars before addressing highs because of the tendency to rebound from lows.
When looking at your own reports, don’t just focus on what’s out of range. Feel good about your successes! This is a tough bugger of a condition to manage day in and day out. After giving yourself a pat on the back, it’s time to play detective. Take a look at areas that need improvement, and see if you can figure out what may be causing the highs and lows. Here are some questions to ask yourself:
• Are the patterns different on certain days of the week? Certain phases of the month?
• Is physical activity having an immediate or delayed effect?
• Do certain types of foods always seem to make your blood sugar rise or fall?
• Are you always high after experiencing a low? Or do lows tend to repeat themselves?
• Are you often low (or still a bit high) after taking extra insulin to correct elevated readings?
• Are emotional situations affecting your control?
• Does your glucose level vary based on how long you have used an insulin pen, vial, or pump infusion set?
For example, one of my patients, a curbside baggage handler at the airport, discovered that his daytime blood sugar varied based on how much luggage he processed. On the busiest travel days, Fridays and Sundays, his blood sugars were much lower than the rest of the week. A simple reduction in his mealtime insulin on busy days solved the problem.
Another client had nice, consistent glucose readings throughout the week except for certain evenings. A look at her data taught us that choir practice usually preceded her elevated blood sugars. It seems that the passion and emotion she felt while singing were causing an adrenaline-induced rise in her blood sugar. A little extra insulin before practice solved the problem nicely.
One of our young clients, a second grader using a bright pink insulin pump, had very erratic readings when reporting to the nurse before lunch, some highs, some lows, but rarely in range. Her records revealed that the lows were on days she had gym class in the morning, and the highs were on days she had quizzes in the morning. A slight tweaking of her morning insulin based on her level of activity and quiz schedule put her blood sugars back on track.
One more example: a delightful middle-aged woman with generally good control, except a tendency to rise overnight on weekends.
The culprit was going out to dinner with her husband.
I would have told her to never go out to eat, but I would rather not have to take my food through a straw for the rest of my life.
Instead, we discussed carb counting and lower-fat food options at her favorite restaurants, along with basal insulin dosing strategies for preventing an overnight rise when she chooses to indulge.
Electronic devices such as blood glucose meters, insulin pumps, and continuous glucose monitors can provide useful information, if you know what to look for. Beautiful pie charts and bar graphs might look delicious, but they don’t always yield useful information. Below are some of the more valuable aspects of the data reports.
Statistics
When viewing data over the past couple of weeks (or more), focus on the overall average glucose, standard deviation, and percentage of readings that are above, below, and within your target range. The average should correlate well with your HbA1c, although meter reading averages may underestimate if you don’t do much after-meal checking (blood glucose levels [BGs] tend to spike up for a short while after meals and snacks).
The standard deviation (SD) reflects the amount of variability in your readings. Lower is better. If the SD is more than half of your average, your readings include too many extreme highs and lows. An SD that is less than one-third of your average means that your readings are fairly consistent, without too many in the extreme ranges.
The percent of readings (or time) within your target range is the gold standard for assessing the quality of your diabetes management. Though a couple of extreme highs or lows can greatly influence your average and SD, they won’t necessarily wreck your in-range percentage. In your software, be sure to set your target range (the default setting is often unrealistic).
The percent of readings in range (or time spent in range) is the gold standard for assessing the quality of your diabetes control.
In some data analysis programs, detailed statistics are available by time of day and day of the week. These can help to pinpoint the source of out-of-range readings. For example, you might discover that you’re experiencing frequent lows only on workout days or highs on days when you sleep in.
Modal Day Reports
These are my personal favorite reports because they provide a quick visual summary of the quality of blood glucose control at various times of day. (See examples that follow.) Be sure the meal schedule in the software corresponds with your usual schedule; many are preset for the “early bird special” crowd, with meals and bedtime at very early times of day.
When looking at a meter modal day report, ask yourself: Are there frequent highs or lows at certain times of day? Are the readings consistent or widely scattered? Are the readings taken at relatively consistent times of day or haphazard? In Figure 4.12 , many of the fasting (wake-up) readings are elevated, but this could be an after-effect from the frequent lows seen at bedtime. There are also some very high readings before dinner that may need to be addressed.
CGM software can superimpose multiple days of sensor data onto a single report. The overlay report, sometimes referred to as a spaghetti graph, provides unique insight into the ebb and flow of glucose levels on a typical day, helping answer questions such as:
• When are most highs and lows occurring?
• Are mealtime insulin doses returning glucose to normal following meals?
• Are glucose levels peaking very high after meals?
• Is there an upward or downward trend overnight?
• Do lows trigger rebound highs?
• Are lows occurring without warning signs or symptoms?
Figure 4.12: Example of a blood glucose meter modal day report
Figure 4.13: Example of a sensor overlay report
Individual Day Reports
Figure 4.14: Example of an individual day report
Individual day reports provide more detail than can be seen in other reports because, as the name implies, they just focus on a single day at a time. These are particularly helpful when using a pump and CGM, because they can combine the data from both into a single report. Looking at reports for several individual days can reveal:
• how long it takes for bolus insulin to finish working (duration of bolus action)
• the immediate and delayed impact of various forms of physical activity
• whether correction doses are bringing the blood sugar down too much or too little
• glucose patterns that follow meal boluses
• if glucose levels are stable between meals (for evaluating basal settings)
Figure 4.15: Example of a glucose trend graph from a meter download
Glucose Trend Graphs
Both CGM and meter software can generate trend graphs that show how glucose values vary over an extended period of time, such as a month or several months.
By highlighting periodic peaks and valleys, these graphs can shed light on whether adjustments are needed for things like menstrual cycles, off/vacation days versus work/school days, and seasonal variations in physical activity.
Trend graphs are also useful for illustrating control changes over prolonged periods of time.
Gradual upward trends often indicate a need to intensify therapy.
Downward trends may indicate that your therapy is on the right track as long as you are not experiencing hypoglycemia too often.
In Figure 4.15 , the trend graph shows that glucose levels are becoming steadily less erratic and more in range.
Ambulatory Glucose Profile (AGP) Reports
AGP is a standardized report that displays CGM data in a graphic format in order to show typical daily ebb and flow. The report includes a median (similar to an average) line, a dark shaded area that includes the middle 50 percent of readings (25 percent above and 25 percent below the median), and a light shaded area that includes the middle 80 percent of readings (40 percent above and 40 percent below the median). Anything outside of the middle 80 percent range represents the extremes that occurred within that time period.
Figure 4.16: Example of a standard AGP Report
Figure 4.17: An AGP report showing data from a hybrid closed-loop system
The essence of an AGP report is its uniformity and simplicity.
When the dark shaded area reaches beyond the target range, there is reason for concern since a significant amount of time (more than 25 percent) is spent out of range.
It is best to evaluate approximately two weeks of data in order for the AGP report to have validity, since single high or low events can produce significant percentages of out-of-range readings when evaluating only a few days at a time.
In addition, a time of day when the dark range is uncharacteristically wide (looking like a pig in a snake) represents extreme glucose variability.
This may be due to variation in food intake, stress levels, or physical activity at that time of day.