Blood Glucose lows

The other day I had an extremely busy day going to different cities to different stores and to an appointment at the kidney clinic. Starting at noon, I didn’t have time to eat lunch except to grab a sub sandwich to eat in my car. Therefore, I did not take my lunch time insulin. When I got to the next store in a different city, I took my insulin. My BG was already high, then it was fairly low… I had to start eating a candy bar in Walmart or I wouldn’t have got out to my car. Then I snacked on the way home, took my dinner time insulin, but my BG was running quite high. In the middle of the night my dexcom alarm sounded, which I didn’t hear, but my wife did. She woke me up and made me do a finger stick and that turned out to be lower than dexcom was saying. It was one of the lowest ever, if not the lowest my BG has been. It was 2.8 My dr has told me a few times that have really low BG, to my brain, is like having a stroke. My wife fed me apple juice and honey to bring it up, then I was fine. However, ever since then I have felt strange in my head, really almost laid back like I am drugged, no energy and just like a rag doll. Anyone have any thoughts on the effects of severe lows or words of wisdom?

That’s pretty typical for me at least. Severe lows can hurt your brain, at least temporarily. In my experience running around to several different stores with any insulin on board will result in low BG, but lows can happen even hours later. The fuzzy feeling will go away. Your body needs time to recover and your liver needs time to refill with glucose to help with your energy levels.


Lesson learned, we all go low sometimes. I have avoided super low ones for several years.

I find thst I used to over correct for low sugar. Which put me on a roller coaster. Thsts when I would have severe lows.

When I got low now, I eat a small amount of carb like a carb gel or something like juice.

It’s so easy to over do it, I’ve eaten an entire meal after waking up low. The. You need to take more insulin to prevent going high.

A single banana is more than enough for most lows. Of course I have cgm, so I see it coming now. Also my pump dial so Down my 7nsulin preventing a low.

I think it can cause brain damage if it happens often.


@Les4 – I’m sorry you’re feeling the effects of severe low blood sugar. I’ve lived through many in my 40 years of using insulin. You should be able to reverse all these effects within a few days or so. Your goal going forward is to minimize the number of times that this happens. I know, it’s easier said than done!

The best thing you could do is smooth out your glucose variability. The best way to manage variability is using a continuous glucose monitor. Even a temporary period with a CGM can teach you what food, exercise, or other routines raise your glucose variability. This is not an easy problem to solve but is definitely doable.

Lows are usually caused by a prior high. Stop the lows by stopping the highs. Again, this is easier said than done.

I know what you’re feeling as well as the worry about long-term health. This is an important quality of life issue and justifies investing in a viable solution. You could really benefit from the lessons a CGM could teach you.


Thank you for your response. I have had a CGM for many years and love it. It has been invaluable in my diabetes journey. Not sure what I would do without it. I got my CGM right at the beginning when I was having hypoglycemia episodes. It was a great help. Like I said, my schedule for the day got thrown off because of the chores I had to do. I will certainly be much more attentive to my own needs from now on. Thanks.

Thanks for your response. “I think it can cause brain damage if it happens often.” … that is what I am worried about. I usually have everything under control, but Tuesday was an unusual day. I love my CGM too, if I didn’t have it, I might not be here. I know now that I have to be much more careful and look after myself no matter what else is demanding my time. Thanks.

If you are using mM units, your 2.8 translates to about 50 in the U.S. units (mg/dl).

Your brain uses the GLUT3 transport to get its glucose supply. Which means it does not need insulin to take in glucose like our skeletal muscle, and more importantly for this conversation, it means that it is able to get glucose even when it is extremely low.

GLUT3 is a high-affinity glucose transporter. It has a high affinity for glucose. The high-affinity for glucose means that GLUT3 is able to pull in glucose even when it is not available in high quantities.
(The affinity is usually expressed as the Km (Michaelis constant) of the enzyme.)

And that means the brain is usually able to continue getting a constant glucose source, even when the glucose level is very low. Once it gets below 2.2 (about in 40 mg/dl units), that’s when it can become a problem.

Here is a reference, talking specifically about glucose and the brain:

Biochemistry, 5th Edition (Section 30.2):
Glycolysis slows down when the glucose level approaches the KM value of hexokinase (~50 μM), the enzyme that traps glucose in the cell (Section 16.1.1). This danger point is reached when the plasma-glucose level drops below about 2.2 mM (39.6 mg/dl)

Anyway, the point is, it’s not great to be at 2.8, and it can certainly make you feel all sorts of crappy. But your brain was not damaged from that, you still had a little bit of wiggle room left.


Thank you so much for your response and the info. Good to know. I am still feeling the effects of my Tuesday low.


If this had happened to me, I’d blame the hangover-feeling on the rollercoaster; that is, the blood sugar going way up and way down, multiple times, very quickly. A BG of 2.8 (US equivalent 50) is low, but not so dangerously low. Over 46 years of T1D, I’ve had lows in the 40’s and even 30’s probably hundreds of times. Not so much since I’ve had a CGM. Be sure you always carry a sugar source with you, and try not to overcorrect. (I know, much easier said than done). When you’re feeling that low, all you want to do is cram as much sugar as possible.
The rollercoaster is a killer. Like the others have said, you will feel better. Sorry this happened to you. Shopping is much more exercise than you would think.


It sure if you are on a pump. Pumps with auto-control help a lot. Also, you should try skipping each mealtime once per month to see if your basal is set correctly. I.e., skip just one breakfast per month , then a week later skip one lunch, etc.


If you are insulin dependent, the best advice I can give is, you need to prioritize your survival over your convenience.

Eating without taking insulin is dangerous long and short term. Combining later large corrections with meal boluses is dangerous. Driving between cities without having your BG under control is dangerous.

I hate hypo, especially nocturnal hypo. I had a job where I had to unpredictably drive in heavy traffic to get to customer locations which often were job sites with no food available at them. I was always dealing with intentional highs during the day “to stay safe” then fighting to get my fastings down. I eventually worked out a strategy that worked better than luck and convenience. This was long before I had a CGM.

The Dexcom CGM helps but once BG gets above 10mmol/l or below 5 it is even less accurate than it is within that range, (which is +/- 10% on average). The sensors when they work right are good at showing trends. But you can not trust the precise Dexcom numbers, but especially not when you are hyper or hypo. A finger stick meter is more reliable than a CGM sensor, and more accurate over a wider low range. But outside the 5-10 “control” using BGM or CGM numbers for BG correction is a nonlinear gamble.

If you are above 10mmol/l , you will need unpredictably more insulin to drop your BG than you will between 5 and 10. The problem is that whether you use a rapid insulin or a longer duration insulin, unless you take them on a fixed schedule, you don’t know between injections how much is yet to be absorbed into your blood.

What the G6 can tell you is whether your BG has leveled off. If my basal was covered, and my BG was high I wouldn’t eat anything until it did.

Once leveled off I wouldn’t try to make a full correction for it; I’d “micro bolus”. That’s 1/2 the correction using a finger stick, waiting an hour using the G6 to see it was dropping. If it wasn’t, I’d take the other half. After a second hour if it still wasn’t dropping I’d take 1/4 the correction, every hour until it started to drop AND THEN be prepared to handle a low.

I’d do this at hour intervals until I saw it was dropping, then wait until it leveled off for a 1/2 hour. If it was level and in range I’d correct for that. I never go to sleep until I know that my BG has leveled off and is in range.

If you are below 5 you will need unpredictably more carbs to raise it than if you were in range. But if you take more quick carbs than you need to make your BG start rising after 20 minutes, you are likely to overshoot and go high. If you are at 2.8 and have a good sensor, 15 measured grams is a safe start, but I wouldn’t take more if I saw my BG climbing at all.

If you drop as low as you did , you can expect to be more prone to hypo and feel “off” for several days.

If you are insulin dependent, the best advice I can give is, you need to start prioritizing your survival over your convenience.

Eating without taking insulin is dangerous. Combining large corrections with eml boluses is dangerous. Driving between cities without having your BG under control is dangerous. Having a supply of glucose tabs of gel packs withcon reliable, consistent, measured amounts of glucose with you 24x7 for moderate low self-corrections can make managing your BG easier. Having a glucagon kit in your home and your wife trained to use it could keep you alive until paramedics arrive 10-15 minutes after they are called…

My eventual strategy for controlling my BG with an unpredictable work schedule and uncertain food supplies was "brown bagging "lunch every day and keeping a supply of packaged durable food and water in my car and desk. That made all my meals prectable and measured. I continued to do this throughout my career.

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I think you have it backwards. Can you explain how a high bG can trigger a low?

Lows often trigger counter regulatory hormones and they can continue to be secreated for up to 24 hrs. I was tought to NOT make adjustments to counter a high if there was a low within 24 hrs before. The faster one treats a low, the less rebound there is, usually.

Also, I almost always totally crash after recovering from a low. Not bG crash, but I find it nearly impossible to stay awake. I take a nap.

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Over time, one’s body may not secreat as much adreneline in response to a low. Adrenaline causes most of the physical symptoms. The result is you can have lows, even severe Iows, without realizing it’s happening. It’s called hypoglycemia unawareness. It can start out infrequent or mild and get worse over time. It’s not brain damage, but the body adapting to a frequent condition in a way that isn’t so good.


A high blood glucose level often elicits corrective action from the diabetic. With an insulin regimen this means adding some insulin to correct the high. Overcorrection is often the result and that causes a low that needs a food correction. You’ll often hear insulin using diabetics talk about the tyranny of the blood glucose rollercoaster.

I agree with you that preventing or limiting the duration of a low will dampen the effects of counter-regulatory hormones which then can lead to a high. Highs lead to lows and lows, in turn, lead to highs. It’s a chicken or the egg scenario - which comes first?

If you want to break this vicious cycle, you need to break into the cycle at some stage. That’s why I often write that blood glucose variability is the metric that people should pay attention to. High BG variability usually means riding the glucocoaster. It also means, as you’ve observed, a very tiring effect; high BG variability, in my opinion, is the best lens to look through for analysis and fixing the problem.


@Terry4 Ah! Got it! I thought you were saying there was a metabolic response to highs that can make the bG go Iow. By “get rid of the highs,” you meant to take steps before it goes high, so that it doesn’t. Thanks for clarifying.

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@TJG – The most effective technique is to eat, exercise, and dose insulin (amount and timing) in such a way to stabilize the blood glucose. That, of course, is easier said than done! It is possible but often people think the process is “overly complicated” or means that they must openly examine what and how they eat. That’s a highly volatile topic!

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Lows feel horrible in the moment and can take me days to recover from, depending on how severe. I also get flare-ups w/ this other disorder I have (Ehlers-Danlos) from even being in 70s or 80s where I get horrible neck and head pain from the physiological strain of hypo (and worse when below 70, for sure). Plus the brain fog and malaise you mention, yes. That is why in my book lows are to be avoided as much as possible, and are worse than highs. Frequent lows over long time periods can also cause long-term health issues, just like lots of highs for long periods. They’re really horrible.

And, yes, activity has an extremely significant impact on my glucose levels. And, like another poster said, these effects can happen hours after the activity itself, even (it seems like) overnight.

Anyway, you will recover, I don’t have any doubt. And your experience seems normal to me, given how low you went. Lows are not something that will make your body happy, that’s for sure. Even when doing our best, T1D is really hard to manage, so don’t beat yourself up, either. I try my best to learn lessons, but it’s hard, even so. Cheers, Becky

May I suggest you carry glucose tabs or jell with you chocolate isn’t he best to use as it contains fat that slows the absorption. Glad you are ok. Nancy50

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When I have lows at that level, it usually takes a few hours of normal levels and then I feel pretty good. But it does take some time. Am very insulin sensitive so I am quite careful about bolusing. My Omnipod has been very beneficial and my A1C today was 5.7 - which is remarkable considering how many highs I’ve experienced recently. We’re all different and have different reactions to different things. Wish you all the very best with this. Take care of yourself for sure.


I’ve been Type 1 for 43 + years now with way too many lows along this journey. The best thing I learned, & it took me way too long to learn this was to not over treat a low. You, we all need to learn how our body responds. For me a low of 75 requires about 7 or 8 grams of fast acting carbs. If my sugar is 50 I need a bit more. Not an entire candy bar ( which is what I used to eat in the beginning). Find a carb you can carry with you at all times like a jelly candy. Know how many carbs is in the entire piece. Experiment to know how much of that candy you need to bring up a low of 70. I was told by my endo that I should take 15 grams, but, in fact that is not accurate for me. So give it a trial run to learn. Look @ that candy/carb exactly as if it was medicine-and know that the proper dose is crucial. Easier to master than it might sound & it will help you so much. At least it has helped me stay healthy.