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Pop Quiz for Surfers

Not this surfer and not by Mr. Hand.

Definable and reproducible patterns on CGM blood sugar trend plots are meant to be interpreted and used by a Sugar Surfer for immediate self-care decision making. Looking at these plots often and searching for common patterns is part of the practice of Sugar Surfing. Once competent with this skill, the Surfer begin to apply his/her knowledge of what has recently happened (food, stress, insulin doses both basal in nature as well as for meals and corrections) and combines these data with what is happening (or about to happen soon) ‘in the moment”: e.g., a long car drive, a soccer match, birthday party, banquet, or just a quiet afternoon reading a book at home. This is what Sugar Surfing is about: managing in the moment.

To some, especially those not familiar with the use of continuous glucose monitoring, breaking from the dogma of strictly managing to historically identified trends and adherence to strict regimens can be quite alarming. Looking at old blood sugar information and your self-care actions (or omissions) from days or weeks past (i.e., logbook) IS helpful, but only in the sense of giving you the best idea of what might happen next under similar circumstances. You need a rough idea of what to expect and be prepared for the unexpected. Remember: chaos still reigns in diabetes. It has and always will. The best defense is good preparation coupled with frequent action. As Louis Pasteur famously said, “Chance favors the prepared mind”.

Look at the first image. The only annotations are the two blood sugar levels and a dose of insulin. You can estimate the time for each by looking at the timeline across the bottom. This image is meant to challenge you to look beyond the numbers. It’s the PATTERNS that matter. Pattern recognition is a Sugar Surfing skill that must be appreciated and practiced with every glance of the screen. It’s not hard to do nor does it take much time. It just takes patience, consistency and resilience; the three virtues of Sugar Surfing.

Looking at the arrows and the actual number are not as helpful as the trend line itself. It's the trend that shows you direction, duration and rate of change. Only YOU, the Surfer, possess the knowledge of what drives the trend line. Artificial general purpose arrows are not to be trusted beyond what the practiced Surfer can infer from his/her own raw data and life experience.

The answers are displayed on the second image below.

From left to right:

  1. a brief straight line trend (aka “shelf”), followed by;

  2. a 2 hour upward drift (aka “delta wave”), followed by;

  3. another shelf;

  4. then another delta wave;

  5. At this point the high blood sugar level is noticed (it was occurring during sleep).

  6. A dose of 7 units of rapid acting insulin was given.

  7. Next, you see a short period of continued rising BG denoted by the green L (aka “lag”) before the blood sugar trend inflects downward (aka “pivots”) and over the next 2.5 hours a fall in the BG trend occurs (aka “drop”).

  8. As the 7 units of insulin wear off, the fall in BG slows then stops and another shelf emerges.

  9. At this episodes conclusion, the trend line is at a more desirable BG range (at least for this Surfer).


Remember that desired targets depend on the Surfer and the Situation!


This sort of back and forth occurs each day in the life of a Sugar Surfer. With well-practiced moves and experience, a certain air of confidence emerges. A Sugar Surfer knows that BG will drift out of range from time to time (in both directions). The empowered Surfer doesn’t harbor guilt about this. They simply take action to correct it and follow through to ensure their intended result occurs as intended... at least more often than not. There is no shame in a high or low BG level. It’s just a situation to manage.

What is NOT shown here is the most likely reason for the first slow BG rise. It was a slow digesting carb meal eaten the night before. In fact the transition of the first shelf into the first delta wave on the left side of the image represents the waning effect of the first fast acting insulin dose taken for the dinner meal the night before. If this happens again (and it will for this meal), I would consider applying an additional dose as the first delta wave was rising past 140 mg/dl (7.8 mmol). When to act with extra insulin in response to a rising trend is an individual decision and situationally dependent as every practiced Surfer knows.

The second shelf that occurred around 140 mg/dl could easily have been left alone. But as the second delta wave occurred, there could have been action taken earlier had this occurred during waking hours. But once 200 mg/dl (11.1 mmol) was exceeded and this delta wave was discovered, action was taken. My decision to take 7 units of insulin is based on practice and knowing the effective lowering range of fast acting insulins from well-practiced high BG levels (180 mg/dl, for example). I could have easily chosen to give myself a smaller dose earlier in that second delta wave had I been awake and aware.

The 2-3 hours to lower an out of range BG is expected here. The lack of any need to apply the brakes with fast carbs was not needed in this example. Once the last shelf was reached, it remained there through the morning. As readers of the book or workshop attendees know, this means I have a well-balanced basal insulin dose (14 units Tresiba in this case, not a pump).

The point of this post is to look at the patterns of your trend line “in the moment” and not as a weekly retrospective search for trends. You must seek to identify meaningful information that you can quickly turn around and use to steer the trend line in a direction of YOUR choosing. Otherwise, this incredible technology called CGM easily becomes nothing more than a convenient alternative to pricing your finger and that my friends seems hardly empowering.

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