Fasting Is Fraught
I cringe every time I’m told to fast for a test or procedure. Fasting poses a risk for hypoglycemia in people with type 1 diabetes, even when using state-of-the-art technology. Fasting should not be required unless absolutely necessary, especially for routine lab tests.
Saleh Aldasouqi, MD, chief of endocrinology at Michigan State University, East Lansing, Michigan, has published several papers on a phenomenon he calls “Fasting-Evoked En Route Hypoglycemia in Diabetes,” in which patients who fast overnight and skip breakfast experience hypoglycemia on the way to the lab.
“Patients continue taking their diabetes medication but don’t eat anything, resulting in low blood sugar levels that cause them to have a hypoglycemic event while driving to or from the lab, putting themselves and others at risk,” Dr. Aldasouqi explained, adding that fasting often isn’t necessary for routine lipid panels.
If fasting is necessary, as for a surgical procedure that involves anesthesia, the need for insulin adjustment — NOT withholding — should be discussed with the patient to determine whether they can do it themselves or whether their diabetes provider should be consulted.
But again, this is tricky even for endocrinologists. True story: When I had my second carpal tunnel surgery in July 2019, my hand surgeon wisely scheduled me for his first procedure in the morning to minimize the length of time I’d have to fast. (He has type 1 diabetes himself, which helped.) My endocrinologist had advised me, per guidelines, to cut back my basal insulin infusion on my pump by 20% before going to bed.
But at bedtime, my continuous glucose monitor (CGM) showed that I was in the 170 mg/dL’s and rising, not entirely surprising since I’d cut back on my predinner insulin dose knowing I wouldn’t be able to eat if I dropped low later. I didn’t cut back the basal.
When I woke up, my glucose level was over 300 mg/dL. This time, stress was the likely cause. (That’s happened before.) Despite giving myself several small insulin boluses that morning without eating, my blood sugar was still about 345 mg/dL when I arrived at the hospital. The nurse told me that if it had been over 375 mg/dL, they would have had to cancel the surgery, but it wasn’t, so they went ahead. I have no idea how they came up with that cutoff.
Anyway, thankfully, everything went fine; I brought my blood sugar back in target range afterward and healed normally. Point being, type 1 diabetes management is a crazy balancing act, and guidelines only go so far.
We Don’t React Well to Steroids
If it’s absolutely necessary to give steroids to a person with type 1 diabetes for any reason, plans must be made in advance for the inevitable glucose spike. If the person doesn’t know how to adjust their insulin for it, please have them consult their diabetes provider. In my experience with locally injected corticosteroids, the spike is always higher and longer than I expected. Thankfully, I haven’t had to deal with systemic steroids, but my guess is they’re probably worse.