A1c, How low is too low?

Some of the A1c's that I've seen people mention on here are pretty low.  I'm just curious how low is too low and if anyone knows what kind of long term effects can be seen from the difference of acceptable low to acceptable high.  For example, if I have a 7 A1c, what kind of differences can I expect when compared to someone with a 5 A1c?  

I'm trying to get mine down to a 6 A1c. I would be really proud of myself If I could do that. A 7 A1c is a good average, but I am curious like you, I would like to know of anyone has experienced a difference in their health, ie vision, etc...

For the past 3 years I've been in the 5.4-6.1 range for all my A1Cs.  My endo seems to be thrilled with those numbers.  And after 30 yrs of T1, I'm still complication free.  So far so good.  Knock on wood!  I've had some pretty low lows over that time, probably around 30...and the highest I've had, one time when my pump malfunctioned, was 459.  No highs or lows were experienced over prolonged periods though, and I really think that's the key.  If highs and lows are corrected in a relatively short amount of time (hours vs days), then I think the risk of complications is very low.  That's just my theory though....

Hi Kristen,I like your theory.

question then.....many people have told me (its only been about 3 months for me with diabetes) that having lows are more serious and then highs--due to what happens with lows compared to highs. does having lows prevent more complications down the road compared to having highs? so are lows and highs equal then?

Jordan, I have found that having lows more frequently has been overall better for me than when I was experiencing constant highs.  I have more energy, my blood sugars are averaged out better, and overall I just feel healthier.  Nothing scientific here, I may be off, but lows (not too low!) are better in the long run than highs!  Having a low blood sugar, for me, feels worse while I am having it, but it usually comes up rather quickly and I feel better.  As with a high, I can sometimes feel sick for hours and even days.  Constant or a pattern of high blood sugars also leads to kidney problems and eye problems, the list is endless for the side effects of high blood sugars.  I have been diabetic for 20 plus years and still haven't figured it all out.  Hang in there!!

The conclusion of the Diabetes Control and Complications Trial (1993) was that intensive treatment which enabled the achievement of lower HbA1c, despite the risk and prevalence of more hypoglycemic reactions, was preferable to conventional treatment because it greatly reduced the occurence of long-term complications (eg. retinapathy, neuropathy, kidney disease).  It is stated in the article published in the New England Journal of Medicine as such:

"We believe that the risk of severe hypoglycemia with intensive therapy is greatly outweighed by the reduction in microvascular and neurologic complications."

The final figure in the article (reproduced below) shows their findings with respect to HbA1c and the progression of retinapathy:


The left graph charts Glycosylated Hemoglobin values (HbA1c) (x axis) against the rate of progression of retinapathy (y axis).  The right graph charts Glycosylated Hemoglobin values (HbA1c) (x axis) against the rate of severe hypogolycemic reactions (low blood sugars) (y axis).  Again, their conclusion and recommendation is to strive for the lower HbA1c values regardless of the greatly increased number of low blood sugar reactions.

Thanks for posting these charts.  It looks like the 5.5 to 7.0 is a pretty good range.  I think the risks involved with severe hypoglycemia can be greatly diminished if you're careful and prepared.  Granted, I've heard from my doctor what can happen during prolonged periods of severe hypoglycemia, and it's not good, but I think for the most part that can be avoided.  Careful monitoring and having people around you with knowledge of your condition seems as if it would almost erase the possibility of  suffering from severe hypoglycemia for long periods of time.  I think if I could get mine in the 6-6.5 range that would be pretty good. 

This is an interesting subject for discussion.  I have been part of the DCCT study and its follow portion, EDIC.  When I first started in 1987 my A1C was over 10.  The push was on to lower that number, which I eventually did.  The study determined in the mid 90's that a lower A1C did in fact reduce complications.

I maintained a low A1C for many years but an unintended result of trying to keep lower readings is the increased chances of hypoglycemia.  I eventually had to quit work because I was unable to recognize low blood sugars at work and home, having frequent visits from the paramedics. I have not worked for 6 years now.  My episodes of low blood sugar with a need for medic intervention has been greatly reduced.  The last time was just a result of giving a bolus but the dinner was delayed.

I also participated in the recent study by JDRF on CGMS.  The dr for this study also participated in the DCCT/EDIC study.  He is also a T1.  He acknowledged that the original intent to lower A1C's produced the unintended consequence of hypoglycemia unawareness.  Since then he encourages trying to maintain an A1C between 6.5% and 7%.


I can understand Rich's situation.  My father has had T1 for 35 years and he was always told to keep his sugars as low as possible.  The result is an inability to feel when his sugar is low.  He is extremely active an within minutes he can changed into a totally different person.  Over the years he's had some seriously scary hypo's.  His testostrone kicks in and his physical strength becomes equal to 10 men even at his present age, 66.  Either way his A1C's have never been extremely low so he maintains a decent average.  Unfortunately for him these hypo events have caused damage to his brain (this is not to mention just the general cuts, scapes, bruises that might happen during the hypo).  The bottomline is your brain needs sugar.  If it's severely deprived, brain cells will die. 

I personally don't concentrate too much on A1C results because it is only an average.  I believe extreme fluctuations in your sugars are just as bad for your body as mantaining high sugars all the time.  My goal at this point in my life is to maintain a consistant level.  I don't like going under 70 or higher than 170 ever.  Not to say it doesn't go beyond those ranges because it does.  But on a normal day to day basis it doesn't.  During my high school and college years, my A1C's fell in the high 6 to low 7's.  But to be honest my sugars were swinging big time.  I would go from 40 to 400 and everything in between.  Now,my A1C's stay in the upper 5's (I started paying more attention when I was preparing to conceive my son).  So do I feel better - you bet.  Keeping your sugars as even as possible is a goal that everyone, not only people with diabetes, should have.