Sugar Surfing Lesson #10: Why does my blood sugar change unpredictably?

Whenever I’m asked about why someone’s blood sugars seem so unpredictable and hard to control, I just envision some of the possible reasons why and how this can happen. The reasons for this variance are NUMEROUS. Most of them are not mutually exclusive. In fact, when you consider the number of possible combinations of 1 or more of the reasons listed below, the number is too staggering to calculate. Many of these possible explanations are either unknown or underappreciated. Some are fortunately rare.

Sugar Surfing™ assumes that our blood sugar levels are in constant motion. I call it “flux and drift”. In 2008, I said The only person with a straight-line blood sugar is a dead person”. If you review some of the list of possibilities below, you might even add a few I’ve left out.

The teaching point is simple: glycemic variance is baked into all of us. Many of these variables can be learned and effectively managed using Dynamic Diabetes Management methods (Sugar Surfing). Others can only be responded to ‘in the moment” when they happen or are discovered. Sugar Surfing is always part proactive, part reactive.

Next time you find yourself perplexed by an unexpected change in blood sugar (either up or down), pull up this list and consider some of the possible reasons. As your surfing skills improve and mature, this list will start to become intuitive. Some of these are very uncommon. You will ultimately develop your own list of "usual suspects" and develop effective tactics to counteract them. Reading the book Sugar Surfing and/or reviewing previous posts on this page are your best first step resources.

This list IS NOT all inclusive, but it's a start. Hopefully, your view of the "glycemic universe" just got a little bigger!

Factors with the potential to impact blood sugar control which good Sugar Surfers should be aware of:


Insulin type (rapid, fast, intermediate, long acting) and action

Amount of insulin taken

If on pump: normal bolus, extended bolus or combination bolus

If on pump: use of temporary basal rates

Injection/infusion site on body or route (injected, pump or inhaled)

Injection into fatty areas (lipohypertrophy slows insulin absorption)

Insulin antibodies (can bind and delay insulin action)

Kidney function (reduced kidney function = prolonged insulin activity)

State of insulin (partially disintegrated due to heat or freezing)

Factors which influence absorption of insulin from site (hydration status, exercise)

Frequency of dosing (overlapping effects of one or more insulins types; stacking)

Timing of insulin dose relative to the meal or snack eaten

Use of insulin for correcting out of range blood sugars (under dosing, overdosing, use of fixed dose corrections)

Insulin pumps (multiple basal rates, wrong times on pump, air bubbles in tubing, tunneling at the site, dislodged site, improperly inserted site, degraded insulin from prolonged reservoir use, programming errors)