January 29, 2013

Alternate-site Blood Glucose Testing

I had not thought to do a blog on alternative site blood glucose testing. I am doing this at the good natured ribbing I am taking from one of the people from the site where I do some peer mentoring. She is a person that uses an alternate site and is thankful I covered it for her and did give the warnings about when not to use alternate sites. She sent me some URLs and said I had better use this topic. So for her I am writing this blog.

I admit that I very seldom use an alternate site because I use insulin and prefer the now factor in my test results. Most of the alternate sites are shown in these images.

The above also shows other areas that people do use for testing. I would say that you will need to experiment to find out what works for you. Basically the hands give the more accurate readings and are current. I have not run into anyone that uses the marked areas of the earlobes so I cannot speak for that.

The biggest warning is for those that have had hypoglycemia. Do not use alternative sites as the readings are from 15 minutes prior on the arms and about 20 minutes prior on the thighs. The calf area is about 20 to 25 minutes prior. Why the lag time?  The BD dot com site gives this explanation, “With all meters, routine testing on an unrubbed forearm, upper arm, thigh or calf gives a test result that is 20 to 30 minutes old. We will call these sites 'lagging' alternative test sites. The fingertips and the palm hold the most recent 'memories' of your blood glucose. Fingertip and palm testing tell you what your blood glucose level is right now.”

Basically this means if you are going low, the readings from alternative sites may be 20 to 30 minutes old and not an accurate reading of where you are now. This you need to be aware of, as relying on readings from these sites during hypoglycemia, may delay correction and cause your death. So at times like these, rely on your finger blood glucose readings.

The U.S. Food and Drug Administration gives these guidelines:
1. People with hypoglycemia unawareness should not use alternate site testing at all.
2. Don't use alternate sites when a seriously low blood glucose might go undetected:
  • When you have just taken insulin, or any time during or after exercise.
  • When there are unknown variables occurring in your day, such as illness.
  • Any time you just feel "low".
  • Whenever you are about to drive.”
Like most sources say – talk to your doctor before using alternate-site testing and please, please ignore the television ads that say you don't need to test on your fingers anymore. All they are doing is taking advantage of people that don't stay in touch with their doctors and basically do little talking during an appointment. My endocrinologist did ask me about some of the TV ads about alternate-site testing and I explained that was a fabrication as far as I could see and I would not test there because I am on insulin. The doctor thanked me for that and said he had two patients that had fallen for the TV ads and wanted prescriptions for the test strips. The office would not give prescriptions since they were on insulin. Both doctors spent quite a lot of time going over the problems if they were having hypoglycemia. They did not think they had convinced them not to use alternate-site testing.

The FDA site also says the following. Can you test blood glucose from sites other than your fingers? Some meters allow you to test blood from sites other than the fingertip. Examples of such alternative sampling sites are your palm, upper arm, forearm, thigh, or calf. Alternative site testing (AST) should not be performed at times when your blood glucose may be changing rapidly, as these alternative sampling sites may provide inaccurate results at those times. You should use only blood from your fingertip to test if any of the following applies:
  • you have just taken insulin
  • you think your blood sugar is low
  • you are not aware of symptoms when you become hypoglycemic
  • the results do not agree with the way you feel
  • you have just eaten
  • you have just exercised
  • you are ill
  • you are under stress
Also, you should never use results from an alternative sampling site to calibrate a continuous glucose monitor (CGM), or in insulin dosing calculations.”

If you are a person with type 2 diabetes and have it well managed, then talk to your doctor about using alternate-site testing.  One last fact, alternate site testing can also be painful.

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