Wednesday, November 2, 2016

CGM Trial and Error

At the beginning of pregnancy, I wrote a little bit about choosing settings for my CGM. What kinds of goals would I set for my blood sugars? Coming up with rules for diabetes management is not an easy thing, and I tend to rely on A1C values to tell me whether I'm pointed the right direction or not. But A1Cs only come once every three months, and something has to be done in the meantime.

When I chose those pregnancy settings for my CGM, I had only been on the CGM for about four months. Because we had just moved to a new town, I was still looking for a doctor and hadn't yet been for an A1C blood draw. My first A1C on the CGM was 7.1%, and that was taken in late April. I assumed it was a little high because I hadn't been as disciplined about my blood sugars before pregnancy started, and thought that keeping a tighter watch on the blood sugars and my food intake would bring it down below 6.0%.

My next A1C was taken in July, and it was 6.2%. Not quite as low as I'd hoped, but still good enough for baby, I assumed. I don't remember what all my A1Cs have been during all my pregnancies. I do know that I had a 5.2% which occurred during the months when I almost drowned myself in a bathtub with a low blood sugar, so that made me think that aiming for 5.5%-6.0% was probably best. I didn't want to be trying so hard for a low A1C that I was forced to suffer severe lows in compromising situations (driving, bathing, exercising, etc.).

My most recent A1C, taken in October, was 5.9%. The somewhat high number was a source of some dismay to me, because my monitor readings were really very good during the six months prior, yet I was barely inside my the target A1C that I'd been shooting for. In addition, my Dexcom clarity report indicated an estimated A1C of 4.7% for the same time period. Confusing and a little upsetting.

When I wrote about my growth ultrasound of 32 weeks, which showed a baby that was a bit on the large side, the anxieties I was having about the CGM readings and its apparent inaccuracy were very present in my mind. Evening calibrations were regularly showing up 20-30 mg/dL higher than morning ones, and that made me unsure of whether my blood sugar was being accurately reflected on the monitor the rest of the day. I assumed that if my blood sugar was actually 20-30 mg/dL higher for most of the day (and night?), that would explain why my true A1C was so much higher than Dexcom's estimate.

So my sensor receiver may tell me that my blood sugar is 55 when it is, in fact, 75 on my glucose monitor. Except that there are times when the monitor says my blood sugar is 55 and it actually is. No, I haven't figured out yet how to tell the difference. Also, I usually love being at 75, except when I don't. Sometimes 75 feels really terrible and lightheaded and weak and shaky. Likewise, I usually feel pretty junky at 55, except when I don't. Sometimes 55 feels as normal as 75 usually does.

So then comes the question: what to do? What are the rules for this situation? I have to write a whole blog post to explain it to myself and I'm still not sure I understand it. There's no way I can squeeze all this information into a 15 minute endocrinology or diabetes education exam. I've just got to make up new rules for myself as best I can. I've finally decided, as with other pregnancies, that I probably just have to be comfortable riding a low blood sugar line that most people are not used to and that most endocrinologists caution you to avoid.

The upshot of it is that I've lowered my target range considerably, hoping to squeeze out the last few weeks at a lower A1C than the first seven months. I have no low alert besides the built-in "Urgent Low" that appears when the sensor reads 55 mg/dL. I even sometimes ignore that if I feel OK and I'm at home and can get food quickly, should the need arise. My high alert is the very lowest the sensor will allow, at 120 mg/dL. I very rarely get above 130 mg/dL, because I begin treating with a modest 3.0 unit correction bolus any time my blood sugar gets to 120 mg/dL.

I was sincerely hoping that the sensor would allow me to avoid the worst pregnancy lows that I've suffered in the past, but the consistent margin of error with calibration simply requires that I assume my blood sugar is a little higher than the sensor is telling me and I have to hang out a little lower than the targets recommended by most endocrinologists (e.g., 80 mg/dL as the ideal reading on the sensor instead of 100 mg/dL as the ideal reading on a glucose monitor). The sensor does, at least, alert me at night when my blood sugar is dropping. That was information I did not have in previous pregnancies. But I still have to keep Gatorade with me everywhere I go, I still have to ask people to help me when my blood sugar gets low while I'm out of the house and I've run out of Gatorade, I still have to hang out at that junky-feeling 55 or 75 for a lot of the day, and I still have to give correction boluses with my fingers crossed, hoping that I'm just the right amount of low two hours later.

No one said having a baby with diabetes was going to be easy! But neither is going to medical school, and I'm pretty sure your endocrinologist thought that was worth it. Sometimes the hard stuff totally is.


  1. Nah, having a baby when you have type 1 diabetes seems way harder than med school. For what it's worth. I'm praying for you every day these last few weeks of pregnancy! You can do it!!!

    1. So you mean I've done something harder than med school five times? Cool. Now I feel a little like a superhero.

      What about residency? Surely residency AND med school make it almost equivalent... :)