Diabetes Management: My Non-Scientific Explanation of Standard Deviation

by Leighann on January 6, 2014

Please remember that I never give medical advice. Ask your endocrinologist or pediatrician for advice about your own child. Make your own informed decisions for your own child.

I’ve heard many parents are perplexed when they look at their meter, pump, or CGM data with their endo and “standard deviation” is mentioned.

So here’s my layperson’s explanation of standard deviation:

Standard deviation is the variability.

Say your BG average is 150.

You can get that average from having a ton of 50’s and 250’s. Or you can get that average from having BG’s mostly between 100 and 200. Or you could have them clustered around 150.

The smaller the standard deviation, the less variability there is. In other words, the BG’s aren’t all over the place.

I wanted to double check that I understood SD from my college statistics courses, so I flipped open my copy of Think Like a Pancreas (read my review).

Scheiner states:

“The standard deviation (SD) reflects the amount of variability in your readings. Lower is better. If the SD is more than half of your average, your readings include many extreme highs and/or lows. An SD that is less than one-third of your average means that your readings are fairly consistent from day to day, without too many in the extreme ranges.”

Gary also says:

“The percent of readings (or time) within your target range is the gold standard for assessing the quality of your diabetes management. Though a couple of extreme highs or lows can greatly influence your average and SD, they won’t necessarily wreck your percent in-range.”

So is standard deviation an important variable to look at? Maybe as part of the overall picture.

Quite honestly, I’d be happy just to be able to download our pump and CGM to my Mac! Let alone actually look at the statistics.

You Might Also Like…

Purchase Think Like a Pancreas: A Practical Guide to Managing Diabetes with Insulin–Completely Revised and Updated written by Gary Scheiner

More posts about the continuous glucose monitor (CGM)

More posts about insulin pumps

More posts about diabetes management

More posts mentioning Gary Scheiner and his books

{ 1 comment… read it below or add one }

1 James October 8, 2015 at 2:47 pm

I was doing some research to see what a “good” standard deviation might be and came across what you have written here.
I’m just curious if you have started using DiaSend to upload your CGM and pump from your Mac. It’s about time! I’m assuming you are using it but just wanted to throw this out there in case you aren’t aware of it.


Leave a Comment

Previous post:

Next post: