Wanna see my dawn phenomenon?

The dawn phenomenon (anyone have a better link for this?) is a powerful beast. One of my reasons for wanting a CGMS was that I was waking up high in the morning, and because of my hypoglycemia unawareness I often didn't know if the high fasting sugars were due to the dawn phenomenon or rebound from a nighttime low.

In July I posted a very nice example of the latter, when I stupidly ignored the Dexcom warning that my blood sugar was dropping, tanked into the 40's, and rebounded.

This morning, I woke up to a high threshold alert (> 140 mg/dL) at about 4:30 am. I fell back asleep (whoops), but I woke up again about an hour later and the receiver showed my blood glucose a little over 200 mg/dL.


The Dexcom Seven manual says never to correct for high or low blood glucose without a confirmatory finger stick. Most people with half a brain* will, over time, learn when they do and don't need the finger stick. I know that when my sugar is trending up, I can usually correct for a high blood sugar based only on the Dexcom reading. So I corrected, my sugar came down, and I didn't hang out for hours with excessive glucose in my blood. Hurray for Comrade Dex. Anyway, I just thought I'd post this so you can see what the Dexcom Seven does for people who wake up high. It is helping me catch nighttime lows, and it is helping me realize right away when I need to ratchet up my early a.m. basal rates.



*This footnote is to acknowledge that some Dexcom users, with whole and functioning brains, will find that they do need finger sticks to confirm every Dexcom reading before making a correction.

Demise of sensor #1, and test strips

SENSOR DEMISE

Yesterday I think my first sensor died. It was a bad blood sugar day to begin with, which didn't help since Comrade Dex doesn't do as well with the highs. After breakfast I went up to the 250-300 range, and darned if I couldn't get it to come down for what felt like hours. Then there was some up and down action, and finally I wrote the day off as a loss.

I had some accuracy issues with the receiver when my sugar was really high, but that's nothing new and I didn't take it as an indication of sensor death. Later in the day, though, I had some long signal gaps, and then a couple hours where it kept asking me for a calibration finger stick. I probably did 4 calibrations before I gave up. About 30 minutes later I did get some more readings, but then it asked for calibration again so I just ripped the darn thing out.

Two points I want to make about this.

First, this sensor lasted just a few hours past 10 days. I am disappointed, I was hoping to get 14, but there you have it. That comes out to just under $6.00 per day. If it had been a 3-day sensor, it would have been just under $3.50 per day.

Second, when I finally admitted the sensor had probably failed and took it out, it was almost 10:00 pm. There was no way I was going to stay up for 2 hours waiting for the new sensor to warm up, so I slept sans Dex, and put in a new sensor this morning. I guess I could have let the alarm wake me up to calibrate at midnight, but for a variety of reasons I didn't want to do that. I hadn't thought of this wrinkle in letting the sensor go until it fails - if it fails late at night you might not realize it, because I don't think it vibrates or anything when there is a signal gap or when it says it needs calibration. Maybe in the future I can learn to read the warning signs of imminent failure, and avoid nights where Comrade Dex doesn't have my back.

TEST STRIPS

Silly me, I thought I'd use fewer test strips once I started the Dexcom Seven. In fact, I used more test strips than normal in the past 10 days. I hope this is because I am getting to know the system, and I need to test more often to learn when it is and isn't accurate. In the past 11 days I have used 81 test strips. I think I've done 4 today (including the 2 for initial calibration of sensor #2), so that's 77 test strips in the 10 days that I had my first sensor. Seven to eight strips a day isn't unusual for me when I'm exercising, but I don't exercise much these days, and I was using closer to 6 per day before I started the CGMS. I hope as I get to know the Dexcom Seven better, the number of test strips will go down, but I guess it doesn't matter too much. Insurance isn't paying for the Dexcom, but they will pay for test strips. Interestingly, the daily cost of test strips vs. daily cost of a sensor that lasts for 10 days aren't too far apart. Funny that so many insurance companies won't consider CGMS coverage, then. Oh wait, did I say funny? I meant horrible, stupid, cruel, and shortsighted.

Why Dexcom?

Once I decided to buy a CGMS, I had to choose from the available models. There are currently three games in town, although Abbott's Navigator should be coming soon. Besides Dexcom, Minimed has two systems - the Guardian and the Paradigm Real Time system (or whatever it's called). The latter is integrated with Minimed's latest insulin pump. I have an Animas IR1200, and my insurance company is not interested in buying me a new insulin pump yet, so the Paradigm was not an option. I chose semi-arbitrarily between the Guardian and the Dexcom. From my research on the internet, it seemed like each system had pros and cons, some people love one, some people love the other, and you can't really know how a system will work for you until you try it. Dexcom had cheaper startup costs, and the Dexcom rep called me back much more quickly. Some people think I'm silly, but I put a lot of stock in the behavior of sales reps to evaluate a company. That was a big reason I chose the Animas pump over Minimed in the first place. After I met with Tim the Dexcom sales rep, and the product looked good to me, I decided to go for it.

Initially they were going to give the the 3 day system for a week, then upgrade me to the 7, but someone behind the scenes decided to give me the 7 right off the bat. I got trained via a 20 minute phone call, and that was that.

Comrade Dex and me

A couple people have asked if I am blogging about my new Dexcom 7 continuous glucose monitor system (CGMS). I have never blogged in my life, but since I am apparently the first person to receive this device commercially (or so the sales rep kept telling me), maybe I’ll give it a shot. I haven’t read other Dexcom blogs, so I’ll probably be redundant to other people with the 3 day system, but I will do my best to be original.

First off, I never used the 3 day system, so I can’t compare the 7 to the 3. I just purchased it a couple weeks ago, and they gave me the 7 right off the bat. I am on my first sensor, and it’s only day 6. At $60 a pop, I will use each sensor for as long as possible.

Starting off the experience was the sales rep meeting. Tim is a very nice guy and gave a good demonstration. He was able to answer my basic questions, but was fuzzy on some of the details. For instance, when giving the spiel about how the higher price of the 7 day sensor ($60 vs. $35 for the 3 day) actually translates into lower per-day costs, I pointed out that since most people get far more than 3 days out of each sensor, that is only true if the 7 day sensor lasts proportionally longer than the 3 day sensor. He seemed thrown by that one. I also asked if the sensor was actually different, or if they just asked the FDA to let them market the original sensor for 7 days. He didn’t know. Some things in the 7 system are different – for instance, the transmitter is redesigned to fit more tightly to the pod, allowing 7 users to shower and swim without using a patch. That doesn’t seem to have anything to do with 7 days, though. He did say it’s more accurate than the 3 day, but I don’t know if that’s a difference in the sensor, or improvements in the transmitter and receiver. Since I am only on day 6 of my first sensor, I don’t know how long the 7’s will last, but my guess is that the per-day cost will be higher than the 3. Since I am a nerd, here is a chart to show what I mean:

For anyone who has been using the 3 day sensor, a rough guide is to take the number of days you usually get per sensor, double it, subtract a few, and that is about how many 7-sensor days you need to get the same per-day cost. If your 3-day sensors usually last 10 days, you have to use the 7 sensors for almost 18 days to break even. If you get 21 days out of the 3, you have to use the 7 for a whopping 36 days before the 7 starts to get cheaper. So yes, the 7 is cheaper than the 3 if you only use it for the specified number of days, but we all know most people use them as long as they last, so it is disingenuous to claim the cheaper costs as a selling point for the 7. Maybe the improvements in the new system will help people not resent paying more for the 7, but heck, let’s be honest about the expense, since most of us are paying for all or part of these systems ourselves.

All this said, I don’t want to come down too hard on these companies. I know a lot of money went into development of Comrade Dex, and I am very grateful to have it. It feels like a miracle to spend time with my toddler and not worry (quite so much) about crashing while I’m taking care of him. Now if only I can figure out how to get it to sense my high blood sugars at night, but that’s another story.