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Permalink Reply by Marps on March 8, 2010 at 11:22am

I've had the Dex for a little over a month and I LOVE it.

My Hypo is set at 60 and the automatic Hypo alarm is set at 55. You cannot re-set the automatic Hypo alarm.
I set mine slightly higher because the Dex is actually reading 15 minutes BEHIND your finger sticks. And when the Dex is out of your target range (between 80-120) it gets to be slightly "off". The last thing you want to do is have your Hypo alarm set at 40 (which is already extremely low) and then find out you're actually trending downward and at 30 (almost beyond help when sleeping)

You can set the alarm to Beep, Vibrate, or Beep & Vibrate
It will alarm every 5 or ten minutes until you hit the "Ok" button.
which means that while your'e sleeping, it will keep beeping every 5 or ten minutes until you wake up.
(Great safety feature)

Also, if you have the alarm on Vibrate, but you ignore it for more than 5 times (I think?) then it will start alarming too.
(this feature has saved my butt numerous times in the past month already)

I put my Dex on the nightstand next to my headboard. When it's right on the wood top, it's really really loud and annoying if the alarm goes off. Which is a surefire way to get my butt out of bed.

If you're considering getting the Dex, do it.
It has completely revolutionized my entire way of looking at my diabetes life.
Really.

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Permalink Reply by Marps on March 8, 2010 at 11:41am

yay! Finally! haha.

The only thing with the lows that I've seen is:
During the daytime, my CGM will sometimes read 60 when I'm really at 94. So, if that were to happen while I'm sleeping, it would seriously aggravate me to no end to be stripped of my beauty sleep for a false alarm... every night. Do you see this too?

I guess it depends how accurate it is on how you're trending before the reading?

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Permalink Reply by Xanthasun on March 8, 2010 at 2:20pm

Thanks for the replies guys! and especially the reminder that it lags.

I had this worry that it would suddenly go off at 55 while at work and be totally noticeable to coworkers (whom I have not for the most part informed) and not that it's a good thing...but 55 is very functional for me so I don't really want a crazy alarm during the day...but at night would be great. So it's good to know about the vibrate setting too.

I'm seeing my endo this friday so hope to get the paperwork done by then :)

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Permalink Reply by Helmut on March 8, 2010 at 5:54pm

5.3.3 LOW GLUCOSE ALARM
The Receiver also has an automatic Low Glucose ALARM set at 55 mg/dL. This ALARM is a feature in addition to your personal glucose alerts. You cannot change or turn off this ALARM or its re-Alert settings.
• When your SEVEN PLUS glucose reading is at or below 55mg/dL the Receiver will notify you with 4 low beeps and vibration in this order:
- 1st 5-minute ALARM: “Vibrate”
- 2nd 5-minute ALARM: “Vibrate” “Beep” “Beep” “Beep” “Beep”
- 3rd 5-minute ALARM: “Vibrate” “Beep” “Beep” “Beep” “Beep” (louder)
• The Receiver will vibrate and beep every 5 minutes after the 3rd ALARM if your readings are still at or below 55 mg/dL until you press the C button.

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Permalink Reply by Xanthasun on March 10, 2010 at 9:21am

Thanks for the additional info. I had seen that it couldn't be turned off/changed...but not about how the alarms change every five minutes.

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Permalink Reply by Ricardo on March 11, 2010 at 6:30am

Marps Wrote:
My Hypo is set at 60 and the automatic Hypo alarm is set at 55. You cannot re-set the automatic Hypo alarm.
I set mine slightly higher because the Dex is actually reading 15 minutes BEHIND your finger sticks.

The only thing with the lows that I've seen is:
During the daytime, my CGM will sometimes read 60 when I'm really at 94.

Danny Wrote:
My system lags a few moments, so I keep my low alert at 80 mg/dl. The first few weeks after having the unit, my setting were at 70 mg/dl. I was finding that I was already in my high 50's or low 60's by the time I was treating my low blood sugar.

Hi Danny and Marps,

My understanding is that Dexcom improved on lag time. The often quoted 15 minute lag time applies to MM and Navigator sensors. I have seen quotes of the Dexcom lag time at 3 - 5 minutes. This is why Dexcom tells you that you do not have to wait until your BG is stable to calibrate the sensor. Both MM and Navigator require stable BG.

Technically Dexcom distinguishes their sensors by measuring BG in serous fluid (as opposed to ISF). MM uses a stainless steel sensor, Navigator coats theirs with a polymer and Dexcom coats theirs with substances to promote vascularization at the sensor. They all are using the same basic technology with slight variations. Dexcom's approach lessens the lag time and gives them the longest rated sensor life (7 days) over the competition.

See this post by Dexcom where they talk about the difference with the Dexcom and he quotes an average 5 minute lag.

As for the discrepancies you are seeing between the sensor and a fingerstick, I personally would consider those variances intolerable. After using the Dex for over a year I don't consider the sensor as tracking well if the difference is no more than about 10 points. My observation has been that as long as I am in the euglycemic range, I can maintian the difference at less than 5 points. When my BG goes into the hyperglycemic range, I notice the calibration starts to drift, so that when my BG comes back down, I start to see differences like both of you have quoted.

I usually start to feel hypo at about BG 55 - 65. My expectation is that the Dex will read no more than 5 - 10 points higher.

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Permalink Reply by Ricardo on March 11, 2010 at 6:50am

One additional statement:

To get the Dexcom vs fingerstick difference down to 5 points, I have to calibrate at stable BG. Dexcom reduced lag time, but they have not eliminated it.

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Permalink Reply by Marps on March 11, 2010 at 7:42am

I've only had the Dex for one month (maybe five weeks now? So it's a newer model) and I'm calibrating it at LEAST 5 times per day- probably more. I'm still doing finger sticks 10+ per day in ADDITION to the Dex readings. I'm still seeing variances.

Just a few mintues ago, Dex was reading a stable (more than two hours straight line) of 205. I did a finger stick and I am at 152 and stable.

I'm definitely seeing variances, but again, I don't use the Dex to tell me what my BG is. I use it to tell me if I'm stable, rising, falling, or severely rising or falling. It's helped a lot.

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Permalink Reply by Ricardo on March 11, 2010 at 8:57am

Hi Again Marps,

Wow, that is a large variance. When I first started w/ the Dex, I saw that kind of variance. Since then I have learned how the Dex works with my body and can get better performance out of it.

I only calibrate twice per day if I can minimize the time my BG goes over 160. I find that this prevents the calibration from drifting, which for me seems to occur at BG of approximately 160 and greater. If my BG does go above 160 for extended periods of time (such as a failed infusion set or illness), I will calibrate 3 or 6 times that day to try and re-establish the calibration accuracy. As I stated previously, for the most accurate calibration, I will try to wait until my BG is stable (such as less than a 10 point change over 30 - 60 minutes).

I also will restrict my calibration to BG roughly 50 - 150, since I have my alarms set at 70 and 140. I find that a more narrow calibration range gives better accuracy within that range. My opinion is that calibrations at, for example BG of 200, will decrease the accuracy of the calibration when my BG goes back to the euglycemic range, which also happens to be the range where I want to spend the most time. The downside to this approach is that I tend to have poor accuracy at BG over 160, since I never calibrate there, but I accept this since my goal is to minimize the time at these levels. For accuracy at BG > 160, I resort to fingersticks until my BG comes down and then I can rely on the Dex again.

Another thing I do is when I see a calibration reading that differs more than 15 - 20 points from the Dex, I will do one or two more additional fingersticks and average the results before I enter the reading in the Dex. Remember, most BG meters are rated at +/- 20% accuracy. IMHO, I feel the average may be closer to the true reading than a single fingerstick. I don't have the link right now, but Freestyle published a report where they show that their meters can obtain +/- 10% accuracy more than 90% of the time. For this reason, I switched from the OneTouch to the Freestyle Lite.

Again, my opinion is that when everything is working right, a 5 point or less difference is darned good enough for me and will not make an appreciable difference in the amount of insulin I take. So despite what the manual says, if I minimize hyperglycemia and continue to see < 5 point differences during calibrations, I do rely on the Dex reading without a confirming fingerstick.

YMMV

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