Double BG Spikes After A Meal - Not Enough Insulin?

[maxell]

T2 diabetic for 3 years on 1,500mg Metformin only. Low to moderate carbs (around 100-150g carbs daily). A1c = 5.5-5.9.

Noticed a disturbing BG pattern after I started tracking BG at 15 minute intervals after a meal, Jimmy Moore style. I seem to have two spikes (not one) after a meal. My BG spikes to 130-145 around 30-60 minute mark then comes down to 100-110 around 75-90 minute mark. So far so good and I would be very glad and think my BG is well under control. But at the 90-120 minute mark, BG rises again to 120-130 or so. Not as much a spike as 140 but still a spike. I've been seeing this pattern over and over again. These tests were done consuming "only" 25-40g of carbs.

Why would this be happening? After the 2nd rise, BG does come down for good to 95-110 at the 120-140 minute mark. My educated guess is that this siganls not enough insulin secretion, giving rise to a later BG spike? What do you think?

 

[phoenix]

No idea what it really means but you aren't alone, it happens in some people without diabetes and researchers don't know why either.

A study gave a group of people an OGTT
http://care.diabetesjournals.org/content/26/4/1026.long
They were non diabetic, and glucose intolerant (but not people with diabetes)
They found 2 glucose curve shapes.

“monophasic” when plasma glucose increased after an oral glucose load to the maximum after 30–90 min and decreased until 120 min with a final downward move of at least 0.25 mmol/l between 90 and 120 min.

and

“Biphasic.” Glucose shapes that reached a nadir (low point)after an initial increase and increased again >0.25 mmol/l until 120 min
These people weren't diabetic . Their glucose levels typically reached 150mg/l at 30 min, declined to 80mg/l at 90 min and rose again to 115-120mg/dl at 120min.(figures estimated from fig 2in the paper).
They had also had a glucose challenge rather than a low carb meal . The fall in many was far greater than the one you are seeing but yours (just) comes within the definition.

They gave some possible explanations including amount of insulin.

The insulin concentrations (Fig. 2B) have a shape very similar to that of the glucose curve. It appears that they are a consequence rather than a cause of the glucose concentrations, although this is ultimately difficult to assess.

ie the insulin ,as is to be expected was released after the rise in the glucose; the amount of insulin was measured and compared to the overall amount of glucose and this didn't appear to depend on the shape .
Other possibilities were : stomach emptying (didn't test), some involvement of the liver (lower fasting glucagon in those with bi phasic peaks), genes/gender (more females; some weak genetic associations)
All in all they didn't know why some people had biphasic curves . (needs further research) but one might think that these people were perhaps on the way to glucose intolerance but this doesn't necessarily seem to be the case.

"Subjects with a biphasic shape had significantly lower age, BMI, waist-to-hip ratio (WHR), HbA1c, plasma glucose, and area under the insulin curve (insulinAUC) and a better estimated insulin sensitivity and secretion (using validated indexes) than monophasic subjects'

 

[maxell]

Wow, thanks so much for your insight. We learn something new everyday, huh? I never would have detected this pattern if I hadn't checked at 15 minute intervals. I used to check only 1 and 2 hours after. But if my BG curve is biphasic, I could be catching another rising trend after my BG had initially plummetted. It is curious why so little is written about this. My guess is, after the 2 hour mark, the biphasic pattern might resemble a kind of sine waves with the crest and trough getting smaller and smaller. Perhaps that's more modulating than just one big rise and fall, who knows.

"Subjects with a biphasic shape had significantly lower age, BMI, waist-to-hip ratio (WHR), HbA1c, plasma glucose, and area under the insulin curve (insulinAUC) and a better estimated insulin sensitivity and secretion (using validated indexes) than monophasic subjects'