I really dislike the term “brittle.” As a T1 since 1962, it has been tossed at me a lot. I have really thought about this recently. It means: liable to break or shatter easily; unstable, neurotic, uptight.

I made a comment to another T1 when she used the phrase. My dislike of BRITTLE is a life lesson. I’m sorry if I upset her.

Can we find a better word? DOCTORS?!?!

I also dislike this term because I thought it was simply a layperson’s term to signify volatile and hard to control blood glucose levels. Apparently the term is used in both patient and medical professional circles.

I found this description published at a Pub Med, National Institutes of Health website.

Type 1 diabetes is an intrinsically unstable condition. However, the term “brittle diabetes” is reserved for those cases in which the instability, whatever its cause, results in disruption of life and often recurrent and/or prolonged hospitalization. It affects 3/1000 insulin-dependent diabetic patients, mainly young women. Its prognosis is poor with lower quality of life scores, more microvascular and pregnancy complications and shortened life expectancy. Three forms have been described: recurrent diabetic ketoacidosis, predominant hypoglycemic forms and mixed instability. Main causes of brittleness include malabsorption, certain drugs (alcohol, antipsychotics), defective insulin absorption or degradation, defect of hyperglycemic hormones especially glucocorticoid and glucagon, and above all delayed gastric emptying as a result of autonomic neuropathy.

According to the above citation, it is a relatively rare, occurring in only 3 of 1,000 cases of insulin dependent diabetes.

One thing that has bothered me about this term is that assigning it to a difficult to control form of diabetes relieves both doctors and patients of any further responsibility to help solve or mitigate the problem.

Before the days of insulin pumps, CGMs, new insulins, and automated insulin dosing systems, the person with diabetes was essentially flying blind as to their ongoing blood sugar status and veering off into severe hypo- or hyper-glycemia was more common.

My personal experience with reducing blood glucose volatility with a lower carb diet and diabetes technology has lead me to believe, at least in my case, that brittle diabetes was an unhelpful term. Before I discovered the great tools available to me to control BG instability, I could have just thrown up my hands and concluded that I’m a brittle diabetic and there’s no sense in even trying to better my life.

I think the term has been inappropriately been used to give up any efforts to try and stabilize blood sugar levels.

I do understand with the spectrum of personal experiences across the diabetic population, that there are people who live with a combination of physical problems including celiac disease, gastroparesis, allergies, and other hormonal imbalances. These complicating diagnoses can be understood to contribute to extreme blood glucose variability and the assignment of the term, “brittle diabetes.” I feel badly for these cases.

I think, however, that it is likely an over-used term. There’s much we all can do to reduce our blood glucose volatility but it takes some education and persistence to improve.


All three of these things pretty much describe me and my issues with diabetes and although I now have a CGM, eat low carb and use one of the newest insulin regimens on the market, every day is a battle to stay in control. I am not offended by the term brittle but I have experienced Dr.s blaming me for my brittleness even though I am doing everything right.

For me the term brittle gives me an explanation for the ridiculous amount of trouble this disease causes me even though being diagnosed as brittle does not actually help to control my BG’s. Being brittle is not an excuse to give up or shift responsibility. It does however give me a reason for many of those WTF numbers and reactions that really don’t seem to have been caused by anything I’ve done.

I’ve had some of the best Dr.s in the world and some of the worst and the fact is that none of them have completely been able to resolve this issue because they simply do not know how and until somebody figures out the mechanism that causes brittleness then all I can do is try my hardest to stay in control and not beat myself up when nothing works like it’s supposed to.


This blaming is definitely out of line. I think clinicians can be overly influenced by the norms they observe in their cohort of patients. With an incidence of 3/1000, you are likely the only case this doctor will ever see.

I think your CGM traces, if the doctor observes carefully, can demonstrate that your volatile patterns are not likely caused by surreptitious misbehavior.

Are you able to present insulin, food, and exercise data graphs over the glucose traces? If you don’t mind me asking, are your CGM standard deviations high, like over 50 mg/dL? It seems like just being aware of these unexplained BG excursions via the CGM would elicit counter-moves from you.

Any Dr. who blames me for being brittle never sees me again so I’m not having that problem with my current Dr.

By deviations do you mean my range? My range is currently set for 70-170 but I have an alarm set to go off at 150 as an attempt to stop highs. What point works best for you to prevent highs?

My doctor definitely wouldn’t consider me brittle, and while I also wouldn’t use the term, I do have blood sugar that I feel is far more volatile than most who put in an equivilent effort.

Even with testing 6-8x a day, using a pump and CGM, making course correctiosn often (I average 15 boluses a day, plus one or more temporary basal rates), adjusting pump settings often based on my BG, eating a very low-carb diet, cooking all my food from scratch, weighing or measuring almost everything I eat, and exercising each day, I still have a standard deviation of 2.5-3.0 mmol/L (45-55 mg/dl), daily highs and lows, and at times prolonged and/or extreme hyper- or hypoglycemia.

My control is considered excellent by my doctor because of the amount of daily effort I put in, but I feel like others who put in the type of effort I put in on a daily basis typically have significantly better control than I’m able to achieve. Compared to the average person with Type 1 who tests a handful of times a day, doesn’t use a pump or CGM, doesn’t adjust their own insulin doses, and eats whatever they want my control is good. I’m positive (from experience) that if I followed those latter routines my blood sugar would never be in range.

My main problem with the term “brittle” is when people use it who clearly have not tried all options available to them. I have seen people say they are “brittle” but have never tried a pump, never tried a CGM, never tried a low-carb diet, never tried adjusting their own insulin doses. If that’s the case, how can they possibly know whether they have brittle diabetes? If they have tried all of those things and still have wildly fluctuating blood sugar, then they can use the term more appropriately.


Standard deviation (SD) is the amount by which blood sugar fluctuates from the average. If your standard deviation is 30, it means that most of your reading stay within +/- 30 mg/dl of your average blood sugar. So if your average blood sugar were 100 mg/dl, an SD of 30 mg/dl would mean that most of your readings stayed between 70 and 130 mg/dl. If your standard deviation were 60 mg/dl at the same average, then most of your readings would stay between 40 and 160 mg/dl. So you can see that someone can have the same average (and A1c) but have different standard deviations or more or less fluctuation in their blood sugar.

Stanard deviation is usually calculated by most software that can download diabetes data. It is a useful statistic to keep track of if you are trying to improve control (as is average and time in range).


Complicating the discussion is the fact that the medical definition has changed over time. Since the term was coined in 1934, doctors have interpreted it differently in the 1950s, 1970s, and 1980s. From the same site you cite:

When I was diagnosed in 1970, it was used by doctors and nurses as an umbrella term for difficult-to-control patients. Whether they were difficult to control for physiological reasons or because they didn’t test that much and didn’t follow the time’s restrictive diet (ahem) wasn’t really taken into consideration. If your sugars were all over the place and you had lots of lows, you were called brittle. I haven’t heard it used for a long, long time.

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Blood glucose reporting software gives you a standard deviation number. It is an indication of the variability of the data set. @Jen gives a good explanation in her comment.

I see the high alarm threshold as a personal choice that balances your need to be aware of impending hyperglycemia with your toleration of alarms in your daily life. Ideally it will be set at a point where you can take action (go for a walk, take a correction dose, delay a meal) yet not create alarm fatigue. I set mine at 140 mg/dL.

I used to refer many years ago to myself as “brittle”. sigh. that was so self-defeating. I just didn’t have the knowledge, the tools, and the gumption, to get better regulated. It took all 3 of those aspects of controlling bg’s to come together to get my bg’s and bg excursions down to a healthy level. I’m definitely NOT “brittle”.

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It’s most helpful when based on readings from CGMS.

If someone is testing only pre-meal to determine bolus amount (common with MDI, 4x per day routine), the SD would only reflect pre meal BG.

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I’ve heard “brittle” tossed around a lot over the past half century. But I never knew that anyone used it to so narrowly describe such a tiny subset (I would’ve though that maybe 10-20% of T1’s might be “brittle” from the way I’ve heard docs used it.)

The mention of young women, so early in the definition, makes me wonder if maybe they’re taking about something more like an eating disorder. Maybe, given the way other definitions of brittle suggest repeated DKA epioses, overlapping with diabulimia (which again I might think, based purely on anecdotes, is happening far more frequently, at the couple percent level.)

I think in the early days, when they calculated your insulin based on weight, they often thought of this number being pretty accurate across everyone. Then we were using the exchange system for foods, urine testing and or visual BG testing. . One could accurately follow the exchange diet and primitive insulin dosing rules, yet number of carbs would vary greatly and occasionally match up with current carb counting techniques. But most often NOT.

In modern day, with newer faster insulin, pumps or apps with calculators, it may appear we are much less brittle than the old days. But we just have better tools, that reduces the appearance of brittle-ness.

But emotions, hormones, exercise and many other factors still come into play on a daily basis that can make it much more unpredictable for some, and maybe less impact on another.

I recall one doctor saying they could put a type 1 in the hospital, control their food, insulin, and activity levels, and achieve good control 100% of the time. And concluded patients should be able to do the same. Glad he’s not my doctor.

I don’t think my Libre has the software that can calculate SD like @Jen described but my average BG is 140ish and the lowest I’ve gone in recent months is into the 60’s and I go up into the low 200’s for a few hours almost every day and I haven’t been able to stop it. However this is a lot better than I was last year when I was spending half my day over 200 and not able to fix it.

I think the young women comment may refer to the effects of hormones. Puberty and pregnancy and all the hormonal changes for me, without any technology, not even a BG meter, were indescribably difficult.

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I did a trial of 1 Libre sensor, and just checked the data on the reader. The closest to SD might be daily patterns in the history section, as a graph with upper and lower range. But it lacks the distinction of what percent is closer to the average trend, vs occasional outliers.

I think you can load the reader data to freestyle website, where there may be more options, including SD.

You can calculate it easily.
And, in my mind, standard deviation of 50/50 is impossible on a low carb diet. My current basal is 7.1 daily. If I eat 40 carbs per day, my bolus total would be 2.6. That’s an SD of 36%.

I did a quick Google search for “Freestyle Libre reports” and was surprised to not find standard deviation as one of the metrics it calculates. I don’t use the system, so maybe there’s someone else here that can verify whether or not the Libre calculates standard deviation. I find standard deviation a useful bit of information.

The standard deviation we have been discussing is of blood glucose data, not insulin doses.

[quote="Terry4, post:18, The standard deviation we have been discussing is of blood glucose data, not insulin doses

I’ve had T1 a long time. Every time a doctor talks about SD, it is always the relationship of basal to bolus, so that has always been my understanding. Would love some more.