Anticipating and Preventing Severe Hypoglycemia

by John Zrebiec,  MSW, CDE
Acting Chief,  Diabetes Mental Health and Counseling Services,  Joslin Diabetes Center


It is no surprise that anyone with diabetes worries about long-term  complications, and many studies—especially the now-famous Diabetes Control and Complications Trial (DCCT)—have confirmed the importance of avoiding recurrent high blood sugar levels. The DCCT was also one of the first studies that emphasized the importance of avoiding low blood sugar levels, too, especially severe hypoglycemia.

Severe hypoglycemia is not defined by a blood sugar number, rather it is defined as the inability to independently treat a low blood sugar level. We now know that serious injuries can be caused by household accidents and auto crashes related to severe hypoglycemia.

Joslin offers a hypoglycemia prevention workshop based on collaborative research done over the past 25 years with the Department of Behavioral Medicine at University of Virginia.

Recognizing the Symptoms of Severe Hypoglycemia

The results of that research show that the most common symptoms of a low blood sugar (below 70 mg/dl) include feeling shaky, sweaty, pounding heart and lack of coordination. Yet, it is not uncommon for someone with diabetes to lose these classic symptoms over the course of time. In fact, it’s not unusual for someone with diabetes for many years to have lost, or have trouble detecting, the physical and mood changes caused by a low blood sugar.

Clinical research and my own experience working with diabetes patients here at the Joslin Diabetes Center indicate that even if physical symptoms and mood changes disappear over the course of time, the thinking symptoms caused by a low blood sugar do not fade away.

These thinking symptoms may become the best, and perhaps the only, symptoms of hypoglycemia for those who have had diabetes for a long time. Examples of these thinking symptoms are difficulty concentrating, slowed thinking or fuzzy thinking.

These symptoms typically start at a blood sugar level of 65 mg/dl which should be high enough for someone to independently recognize and treat the low blood sugar. Obviously, as blood sugars drop lower, thinking symptoms can become worse leading to confusion, disorientation and severe hypoglycemia, that is, the inability to think clearly enough to react.

Our research tells us that the most common reason for a low blood sugar (defined as less than 70 mg/dl) is taking too much insulin, and the second most common reason is not eating enough or delaying eating after taking insulin.

But the most common reason for severe hypoglycemia is delaying treating after recognizing symptoms. And not surprisingly, the most common mistake when treating a low blood sugar is over-treating.

Another common mistake is treating with something that tastes good like chocolate or ice cream rather than fast-acting carbohydrate. (The fat content in the chocolate or ice cream slows down the absorption of the sugar).

Our research also tells us that low blood sugars breed more low blood sugars, and the more lows that one has, the less symptomatic they become, and the longer it may take to bring blood sugars back to the normal range.

Our collaborative hypoglycemia research started back in the mid-1980’s with an initial study that found people taking insulin were not as accurate at detecting low blood sugar levels as they imagined. In fact, when asked to guess blood sugar levels based on symptoms before checking, they missed the number by a wide margin 55% of the time.

The most common mistake was that these adults thought their blood sugar level was okay when it was not (too low or high). Subsequent studies with children and their parents have had similar results.

The Risk of Injury

We know from research that most of the hypoglycemia related accidents during waking hours are from car accidents. For example, a few months ago the Boston newspapers carried a story about a woman who drove her car into her neighbor’s swimming pool during a severe low blood sugar. Fortunately, her neighbor was home and dove into the water to rescue her.

Our research has shown that drivers start to slow down to compensate for a low blood sugar, but they also start to swerve on the road. This is why there are now guidelines for driving that include:

  1. checking blood sugars before you turn on the car if you think you might be low.
  2. stopping as soon as possible if you feel low or someone else thinks you are low while driving.
  3. checking and treating low blood sugars, immediately and appropriately.
  4. waiting, as hard as that may sound, to start driving again until blood sugars return to a normal range.

During the night, the most common reason for injury is that people get up to go find some orange juice to treat their low blood sugar and end up falling down the stairs or having some other type of household accident. I recently saw a man who fell down the stairs and broke his leg on his way to the refrigerator for some juice. That’s why it’s important to have something right by your bed to treat a low blood sugar rather than find yourself roaming around the house, confused in the dark.


The ultimate goal is to reduce low blood sugar levels to as few as possible, although eliminating them is impossible if you are taking insulin and striving for tight control. However, the goal is to totally eliminate severe low blood sugar levels that can be potentially harmful, as well as distressing to both you and family members who may have to deal with them.

Click here for information on the hypoglycemia prevention workshop at Joslin Diabetes Center.


  1. As a practicing Type 1 for 44 years I am one of those who have lost the typical symptoms and feelings of low blood sugar. I now make absolutely sure that I ALWAYS have glucose tablets on me at all times and whenever I feel strange I test or I will just take a glucose tablet. and then test. I would greatly benefit if I had a continuous glucose monitor. Are you listening Medicare?
    Medicare is all about prevention so how about preventing severe hypoglycemia?

  2. Hola! vivo en Uruguay tengo un hijo de 5 años con diabetes tipo 1. Me interesa mucho la información que ustedes proporcionan atraves de su sitio web. El tema que mi inglés no es muy bueno y se me pierden muchas cosas de la información. He tenido la oporunidad de leer el libro “Manual Joslin” en español, cuando mi hijo debuto. Me interesa mucho toda la información que ustedes proporcionan. Quisiera saber si ustedes tienen algun sitio o página que se pueda leer en español. Desde ya muchas gracias.

    • Querido Senor Robledo:
      Siento mucho para la repuesta tardia y mi Espanol peor. En Joslin nosotros tenemos una clinica donde los medicos y otros empleados hablan Espanol. Mandare su pregunta a ellos.

  3. As someone who is not diabetic, but very hypoglycemic, it’s so hard for me to believe that people can’t feel low blood sugar symptoms. I have never heard of that….weird. When I drop, I have DRAMATIC and REALLY BAD symptoms that are extremely scary, especially when I live alone and my attacks often happen at night. 🙁

    • Atheria, believe you me there is such a thing as “hypoglycemic unawareness” — especially among Type 1 (insulin-dependent) diabetics who have had many instancesof hypoglycemia, or are presecibed too much insulin over a prolonged period of time. I spent the better part of a year-and-a-half in that situation; I had always been able to recognize low blood sugar symptoms — but mine disappeared altogether in the fall of 1989. I had just begun my first job as a cantor in a synagogue, and was working a full-time “day job” in a stressful atmosphere. One night, I decided to drive one additional block before getting dinner on my way to a rehearsal. By the time I’d driven that block, I was nearly unconscious — and driving through the streets of White Plains NY in that condition. Fortunately, a policeman on his rounds saw me driving as if Moe, Larry and Curly were fighting for the steering wheel. He followed me, and saw me pull into what I thought was a parking spot on a side street in front of a bar. I remember him pounding on the window, asking if I was okay — and he believed me when I managed to say that I was very sick. He looked for my medic alert ID and called the paramedics, instead of a squad car — otherwise I would not have survived. Ths EMTs were wise enough to start me on IV glucose before testing my sugar. With the IV glucose, it was 17. A month or so later, I had an episode in front of my new congregation — and changed diabetologists. I had to stop working, because I never knew when an attack would happen. It took about 5 months, and a stay in an inpatient Diabetes Treatment Unit, before my doctor reduced my insulin dosage to a point where I could feel my hypoglycemia symptoms again.

  4. Still in the learning stages for detecting lows. Initially, least in my case, doctors seem to over prescribe in the beginning – so its important to keep track so can make adjustments in medications.

    My mornings used to be kind of low & doctor suggested having a late snack but instead had me stop taking 1 medication & adjusting another and now I’m in the normal range every morning.

    Still wondering about the lows when I’m out biking or hiking. One time (in the beginning stages of figuring things out) I pedaled to the doctor for routine check up and BG was 30. And I didn’t feel bad or anything. They gave me some chewing gum & suggested I take along a snack when I’m out biking.

    Yikes, lets see how many times it takes to pass the captcha test, its easier taming diabetes than capthcas

  5. John, Right on the money again. I have had a car accident and did not recognize my low blood sugar and it read 18 when the Police showed up. I also have had lows while working out and have solved that problem with peanut butter crackers and sipping Gatorade throughout my workout. In a fast paced world, it is so important to keep an eye out for lows. I have no signs anymore and have had Diabetes since 1988. I know how important it is to take your BS before driving and I know to eat when drinking alcohol. I have learned a lot about taking those extra steps to be in better control through your hard work at the Joslin Clinic. Great Job and I hope your message goes out to those who could learn from your studies. We all need refreshers and reminders that our health is vital to a long and productive life.

  6. For most of my 43 years of type 1, I could almost always see a low blood sugar coming a mile down the road. The last couple of years, though, I have had a few incidents take me completely by surprise – including 2 visits to the ER, never happened before. A CGM helps, but maybe not in the way you think. Since it is ‘behind’ your actual blood sugar by up to 1/2 an hour, it is not the fast acting predictor you may think it will be. But having worn one for a year and a half now, I find it has helped me see my blood sugar trends overall, and learn how to avoid lows. This is a big step foward for me.

  7. I’ve been Type 1 for over 36 years with a terrible and very frequent hypoglycemia unawareness problem. I’ve gone through all the problems that you guys describe and more, you can’t imagine, car accidents, shocks at work, shocks at night while I’m sleeping, in the street, at the store, everywhere, the worst part is that I live alone. I don’t know how I’m still alive . Does anyone know about these trained dogs that can detect low glucose? Where can I buy one and how much is it? I guess it would be a great benefit if I had one. Are you listening Medicare? jajajajaja… I laugh but this problem is not funny at all 🙁

  8. Hi everybody,

    I’ve recently read that some researchers at Oslo Universitry Hospital are looking into a new sweat meter that warns patients of dangerously low sugar and I’d like to know what researchers at Joslin think about it, if you think that it could work in the near future.
    Thank you in advanced,

  9. I have been diagnoses Type 2 in 1994. I would start to feel hypoglycemic at 70. After a few years I wouldn’t feel a low blood sugar until I was around 60. Now I don’t sense it until I reach the low 50s or less. When it does happen it comes on very quickly without a warning. It scares me but I don’t panic. I eat 4 sugar packets 916 carbs) immediately and then test. It is the best feeling in the world to stopthe clammy sweating and shaking.

  10. I have type 2 and I get up some nights with a deep sweat from my shoulders up.
    I know right a way what it is. I take some peanut butter and jelly crackers.
    that seems to work.
    the two packs of sugar sounds interesting.
    Any better than crackers and peanut butter ?

  11. I am a Type 1 for over 23 years. I wear an insulin pump and have managed to keep my lows in hand. They mostly happen after excercise or bolusing too much at meal time. On my night table I keep a juice box and in the drawer glucose tablets. I am lucky though that my husband is a light sleeper and wakes up when I become restless and helps me take care of the situation. Daytime, I am able to do the correction. Living with diabetes is like walking on a bunjee cord! (ha!)

  12. After 23 years of type 1, I just had my first severe hypoglycemia reaction. I awoke at 1:30 in the morning, feeling low. I made it to the kitchen and tested. My BS was 16. I got the OJ out of the fridge. Next thing I knew, I was waking up on the floor. The unopened OJ was still sitting on the table. It was 4:30 in the morning. I called for my husband, who luckily woke up and came to my aid. He gave me the OJ. My BS went up to 23. After some more OJ, I was more “with” it and my husband called the EMT’s, who took me to the ER. The doctors there kept asking me about how much I’d eaten earlier and how much insulin I’d taken. My dinner was at 6:00 pm. I’d dosed my Humalog according to the carbs in the meal. At 11:40 pm, I tested my BS before bed. It was 283. I took no more Humalog, but did give myself my usual dose of Lantus. I have double checked all my calculations and still can’t figure out how my BS dropped from 283 to 16 in 2 hours. I had no excessive exercise during the day to acccount for the drop either. Any other ideas? Without having any of the usual suspects (too little food, too much insulin, too much exercise) to account for this extreme drop, I’m almost afraid to go to sleep at night. I’ve placed juice boxes and my meter right next to the bed now so I don’t have to walk down the hall to the kitchen, but I really would like some idea why my BS dropped so quickly and so low to cause me to black out. It’s downright frightening.

  13. I’ve been hypoglycemic for years (but not diabetic) and it’s been getting worse with age. In my case, taking multi-vitamins (one-a-day kind) worsened my condition even more, until I found out and stopped taking them.

    Four months ago, totally by chance, I discovered a wonderful natural food product that regulates the pancreas and I haven’t had a single attack since. I also lost ten pounds of weight along the way as an added bonus, as I was able to stop eating multiple snacks during the day.

    The product is Jerusalem artichoke. It can of course be found raw in any supermarket, but I found out that a swiss company (A. Vogel) makes it in liquid form and also in pills. It is stocked in many natural-product stores. One just has to follow the instructions on the label, but I didn’t stop after 6 weeks and kept taking it, since my purpose is not weight loss.

    What a relief to be normal and only eat three meals a day, without the frequent food craving, body weakening, shaking and sweating everytime tle blood sugar level goes haywire. I hope it works for other people as well as it did for me.

  14. I have type 1 diabetes for almost 15 years. I have always thought that hypoglymecia is only an issue affecting me, assuming that I’m just really bad at managing my diabetes. But after searching the internet, I realized that it is also a concern for a lot of people with diabetes too. Since I experience hypoglycemia often, I always make a point to carry a bottle of juice w/ me. But I find this very inconvenient since I really don’t get to drink it when I’m thirsty. So I came up with a design for a water bottle that can store and dispense powder juice. That way we can carry water to quench thirst and allows us to sip juice when needed. Please check out this product design at
    If you think this product developed, manufactured and placed in the market, please vote for it. If you also have inputs on how to make it a better product, your feedbacks are welcomed too! thanks.

  15. I am not a diabetic. But I have extreme sugar lows. It happens without warning and scares me to death I’m trying to follow a diabetic diet to maybe stable my blood sugars and help me loose weight. It’s starting to consume me and my life. I’m finding it harder to focus at work and I’m always dizzy headed after having an hypoglycemic episodes sometimes it last all day and I get weak and tired. Has anyone had these problems?

1 Trackback / Pingback

  1. Gestational Diabetes

Leave a Reply

Your email address will not be published.