The Many Reasons for High and Low Blood Sugars (and why we need a LOT of compassion for ourselves!)

reasons for high and low blood sugars

“Just count your carbs, use your insulin-to-carb ratio to calculate your dose, and voila! Your blood sugars will be perfect!”

…said by no person actually living with type 1 diabetes, EVER.

I have been teaching people with type 1 diabetes around the world for the last ten years what it really takes to achieve healthy blood sugar levels. I’ve also been successfully managing my own T1D since 1980. And I’m here to say, keeping blood sugars in a healthy range is a LOT more complicated than most T1Ds are ever taught.

In this article, I will attempt to cover the many variables, far beyond just carbs, that can affect one’s blood sugar level. Before I cover the many non-food variables, let’s quickly touch on why carb counting alone does not work.

All Carbs Are Not Created Equal

First of all, all carbs are not created equal. If you eat 30 grams of carbs from pineapple, it will raise blood sugar much, much faster than 30 grams of carbs from a low glycemic food, like black beans. Yet timing of how to dose for different types of glycemic foods is rarely taught. The dose for the pineapple will have to be given much further in advance than the dose for the beans. Pre-dosing will allow the insulin to be closer to peaking when the pineapple is being absorbed, which is important since it will cause blood sugar to spike within just a few minutes. The beans, however, might need a split dose. For those on a pump, you’ll want to use an extended bolus, or if on MDI, perhaps 1 unit now and 1 unit an hour later, due to their much slower effect on blood sugar.

How Fiber Plays a Role

Then there is the issue with fiber. Insoluble fiber is the roughage found in many vegetables and whole grains. This type of fiber doesn’t get digested, thus does not affect blood sugar, so we do not have to count this type when calculating carbs. When a label shows how much fiber is in the food, it’s usually 50% insoluble and 50% soluble. Soluble will affect blood sugar, so it is suggested to subtract half of the total grams of fiber from the total carbohydrate count.

Protein and Fat

What about protein and fat? Many people think protein and fat are ‘free’ foods. That is not true. Many will see a slow and steady rise in blood sugar 2-5 hours after eating protein. High-fat meals can cause an increase in insulin resistance for 5-10 hours requiring a temporary basal increase for hours after the meal. This is easily seen with meals like pizza, anything with a lot of cheese or cream, or even after eating a large amount of healthy fats, like avocados and nuts.

The Effects of Caffeine

Coffee doesn’t have any carbs, right? Yes, but it has caffeine, which many studies have shown causes an increase in insulin resistance and a release of adrenaline, which will raise blood sugar. Caffeine is tricky. Some type 1s always see a rise in BG and some don’t. Usually, coffee is consumed in the morning, when blood sugar tends to rise anyway, so it can be hard to tell if the rise is being caused by dawn phenomenon (the natural rise in morning blood sugar caused by the liver’s secretion of glucose) or the caffeine. To help determine this, I suggest drinking black coffee without sweeteners on an empty stomach later in the day, and watch if BG rises or not. But the tricky thing is, even in the same person, sometimes a rise in BG is seen from caffeine, and sometimes not.

Water and Dehydration

Water certainly does not have carbs, right?! Of course not. But not drinking enough water can result in a higher blood sugar. What?? Here’s why: When you are dehydrated, the amount of water in the bloodstream decreases, which makes the existing glucose in the bloodstream more concentrated. While the amount of sugar in your bloodstream hasn’t technically increased, it can result in higher blood sugar level readings because the ratio of sugar to water has increased.

Furthermore, dehydration increases the level of the hormone vasopressin, which pushes the liver to produce blood sugar. Mild to moderate levels of dehydration—especially during hot weather, intense exercise, or illness (diarrhea or vomiting)—can cause blood sugar readings to increase by 50 to 100 mg/dL or higher. When dehydrated, insulin will take effect slower due to it having a harder time absorbing, thus causing a delay in the effect of a bolus.

As if all of that wasn’t confusing enough, there’s more!

When Insulin Becomes Less Effective

If insulin gets too hot or if it freezes, it can lose potency. If the bottle/pen has been open longer than 28 days, it can also lose potency. Anyone who is not good at rotating pump or shot locations on their body has a high risk of scar tissue buildup, and if delivering insulin into scar tissue, this will cause a very frustrating delay and/or reduction in the absorption of the insulin.

The Role of the Liver

The liver is a constant source of glucose streaming into the bloodstream (thus one reason why we need long-acting insulin/basal insulin in our bodies at all times). The liver’s glucose output peaks in the morning hours, or any period of prolonged fasting. It also peaks with any event that causes a release of adrenaline, as well as after an extreme low blood sugar. These types of blood sugar rises are very hard to manage because the amount of glucose the liver is releasing is frankly unpredictable.

Fluctuating Hormones

Speaking of hormones, women’s cycles can also affect blood sugar. Many women will have an increased need for insulin 1-7 days prior to the start of their cycle and a reduced need on day one. Having said that, every female with type 1 should track their BG trends around their cycle to determine what is true for them. Women going through perimenopause, as well as teens going through puberty, will also see an increase in insulin resistance, which can be very frustrating due to its sporadic nature. Some doctors recommend the drug Metformin to mitigate this.


Feelings of stress, anger, and nervousness all release cortisol, which will cause resistance to insulin and a need for more insulin. This can be dramatic if someone suddenly sees police lights in the rearview mirror, or gets a disturbing text, for example. I have seen my own blood sugar spike up over 100 points in under thirty minutes in situations like this. Stress also affects the way we take care of our diabetes.

Chronic stress will also raise blood sugar, but more subtly. This effect can also be seen the day after a poor night’s sleep. Physical stress, like taking an extremely cold shower, can also raise BG. I shot up to 300 after shivering for ten minutes during an ice-cold shower.


Anytime we get sick, the body releases stress hormones like epinephrine (also known as adrenaline) to fight the illness. These hormones can raise blood sugar levels and increase the amount of insulin the body needs. This can also be seen in people who get seasonal allergy symptoms.


Some medications can cause an increase in insulin resistance, such as steroids, some antidepressants, some BP lowering meds, nicotine, estrogens, birth control pills, niacin, and more. Some can decrease resistance, like Ritalin and beta-blockers. Alcohol can actually lower blood sugar, due to the fact that the liver will reduce glucose output to focus on breaking down the alcohol. Yet, this can be hard to see since alcohol is often mixed with sugars and/or eaten at mealtimes, which will raise your glucose levels.

Body Changes

Any increase in body weight will cause an increased need for insulin, and vice versa in the case of weight loss, even if just by a few pounds.

Tech Issues

CGMs and meters often are not 100% accurate and in today’s high-tech world, it’s easy for us to forget this. If a finger used for a blood sample is dirty or wet, this can alter the reading too. If there are bubbles in the pump tubing or if an infusion set accidentally comes out, this will obviously cause blood sugar to rise.

The only time in 40 years with T1D that I ended up in the ER with diabetic ketoacidosis (DKA) was due to exactly this. I ran a half-marathon in the morning and then treated myself to a very high carb dinner. As I finished dinner, I started to feel very sick. I assumed I was just tired and dehydrated from my long run. Soon all of my muscles started to cramp and I felt super nauseous. I became so hot that I remember gingerly rolling myself off the couch to lie down on my tile floor to cool down. I soon realized I needed help. I crawled to the phone and dialed 911. It was not until I was in the ambulance that I realized my entire tubing was full of bubbles.

Temperature Changes

Warmer temperatures cause blood vessel dilation, which can cause an increase in blood flow to the muscles, and thus a drop in BG. The same can be seen after a hot shower or time spent in a hot tub. Some report that cold weather drives glucose numbers down – perhaps related to the body working harder to stay warm. Yet, when you go to an environment with a different temperature, many other factors may be changing, such as your activity level, what you are eating, hydration, etc.


Though most studies related to diabetes and altitude concern the accuracy of blood glucose meters, there are some reports that altitude can increase insulin resistance. However, if you are going to a high altitude to ski or hike, for example, the extra activity can of course drop BG.


It’s easy to think exercise will always drop blood sugar, but this is actually not true. INJECTED INSULIN is what causes hypoglycemia, not exercise alone. This is very helpful to understand. I did not learn this until after living with T1D for 20 years and had very frustratingly stuffed my face with tons of carbs every time prior to being active throughout my childhood. When you fully grasp this concept, it is truly possible to exercise without eating anything!

Every low is caused by excessive injected insulin. Exercise enhances the effect of insulin.  For exercise to cause a low, there must be enough injected insulin in the body for the exercise to activate to cause a low.

If exercise alone caused hypos, then every person who ever exercised would have to deal with low blood sugars, but that is clearly not true. To illustrate this, if someone with type 1 wakes up with a high blood sugar and immediately goes on a walk to bring it down, the BG will likely not come down. Why? Since there has not been a bolus since the night before and the only insulin on board is basal or long-acting, this small amount of insulin will likely not be enough insulin in the body for the walk to cause a low. If anything, it could make the dawn phenomenon worse and actually cause BG to rise.

So the advice to ‘always eat before exercise’ really depends on how much insulin you have on board and what your blood sugar is. The less insulin, the less chance of a low, and vice versa. However, the type of exercise also creates different blood sugar effects.

Anaerobic exercise, such as weight lifting and high intensity interval training (HIIT), can actually initially raise blood sugar due to an increase in glucose production in the body during these types of activities. However, during steady-state cardio – like a long walk, elliptical, or bike ride – glucose utilization predominates, thus there is a greater chance of lows with steady state cardio over anaerobic activities.

With anaerobic exercise, as well as a steady state activity lasting over two hours, something called delayed onset hypoglycemia (DOH) can occur. This is due to the fact that during these activities, a lot of stored glycogen in the muscles gets used up. Thus after the activity completes, the body can be busy for hours replenishing the body’s muscle glycogen storage reserves, thus removing glucose from the bloodstream without the need for insulin. Knowing this is very important because many often think that once they stop being active, their risk of having a low goes away, but not in this case.

Case in point. I completed an intense, seven-hour gravel bike race a few summers ago, and I needed to reduce my basal rate for 48 hours after the ride. Had I not known about DOH, I could have suffered a serious low that night as I slept.

In Summary

In the life of a type 1, calculating accurate rapid doses is our most challenging task. It is a task that must be done daily, multiple times a day, every day of our lives, from the day we were diagnosed, today, tomorrow, and until the miracle of some sort of cure is discovered. Having said that, when you have the right education and support, managing type 1 and staying in range over 70% of the time is absolutely doable.


Additional Resources:

Does Caffeine Affect Blood Sugars?

Staying In Range During and After Exercise: A Real Pain in the…

Drinking with Dr. E and Dr. P: How Alcohol Affects Blood Sugars

Dawn Phenomenon: How to Identify and Manage It

What Is Insulin Resistance and How Do You Know If You Have It?


About the Author

Dr. Jody Stanislaw received her Doctorate in Naturopathic Medicine in 2007. Her TEDx talk, Sugar is Not a Treat, has over 2.8 million views. She has successfully managed living with type 1 diabetes since the age of 7 and now shares her wisdom helping T1Ds all over the world.

Via her virtual Type 1 Diabetes consulting practice, over the past 10 years she has helped thousands of patients all over the world achieve the best blood sugar control of their lives. In addition to teaching patients how to improve blood sugar levels, she also supports patients with key lifestyle areas such as diet, exercise, sleep, and emotional health, which are critical but often left out of standard care.

She has presented over 200 Facebook lives since March 2020. Her videos have thousands of views. Testimonials sharing how her content has dramatically improved people’s lives are endless.

From her 40+ years of personal plus professional experience with type 1 diabetes, she teaches life-changing information about how to successfully manage this complex condition that standard medical care often leaves out. She has private programs, online courses, and a monthly T1D training program.

For more info, visit:

  1. Avatar

    I can’t do this any more. I quit having T1D. I’m tired of dealing with it 24/7. This tamagotchi is going to die.

    • Lee, you are so not alone. I think every single one of us with T1D have days where we’ve said ENOUGH!! I sure know I have too. But then tomorrow comes and we feel better. I know the editor privately reached out to you after you wrote this. Please know there are always fellow T1Ds you can reach out to anytime you are needing support. I have bimonthly group calls, all the FB groups….If you would like to try one of my group calls sometime, send me a note via my website; click ‘contact’ on the bottom of the home page. Here to help, Dr. Jody

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        Thank you. I am over that mood now. I spent a few days in hospital. If I can survive the “care” I had on the ward, I can survive anything!

        • Haha, glad you have a sense of humor about it! But more importantly, glad you reached out for help AND that you are feeling better now. Dark moods eventually dissipate, just like how clouds always clear. It helps me to remember that when I’m having a heavy day.

          • Avatar

            Well I was diagnosed with type 1 diabetes at a local hospital about 3 years ago at age 64. That was a bummer. By now, I am tired of it and I am thinking about going back to the hospital and tell, them, that I don’t want it anymore. They should take it back!!!
            If I only would have gotten it at Costco I would make use of their generous return policy!!!

  2. Avatar

    You have a lot of company in your frustration, Lee! I’d guess just about all of us T1D warriors have had those low moments (pun intended). I also am sure that I’m not the only one rooting for you to keep the faith.

    Thank you, Dr. Jody, both for the validation and for your really helpful suggestions about how to work with our many and constant BG challenges. Great article!

  3. Thank you for this fine summary of why counting carbs is not enough to control blood sugars and spelling out many of the factors affecting BS. After seeing many endocrinologists through the 28 years with Type 1 it got to the point where I wanted to punch them when they asked what my insulin to carb ratio is and how important it is to carb count! And how I need to avoid lows! As if counting carbs and doing sometimes convoluted calculations is the magic bullet for control! I would love to have an endocrinologist who is also Type 1 and understands the frustration and distress of living with this disease every second of their lives, no time off for good behavior or birthdays. Thank you.

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    This review article is one of the best, comprehensive I have read. I have worked with Dr Jody and highly recommend her to folks that are frustrated. She is caring and understanding if the challenges we T1Ds face.

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    This was FANTASTIC and accurate AF. And yet our endos where I work insist that if their patients were just counting the carbs correctly they would not have mysterious fluctuations. Duh. 🤯

    • I’m laughing at the truth of your comment and I totally agree with you! That’s exactly why I’ve committed my career to creating better education for T1Ds. If you’d like to have a free intro call with me, it would be fun to connect and I’d love to support you if you are looking for better support.

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      Ohmygosh! Im so glad to read this article…and your response Karen! I can’t count a carb to save a hippo (not that I want to face one other than I turn into as hangry hippo) due to fluctuating BG numbers. I’m T2D…um no it’s more like T1.5D since I’m all over the board no matter what meds I take or how I eat.
      To Dr. Jody, thank you! I learned a bit more and I sent this link to my T1D family member. Stay well everyone, try not to go insane over diabetes and Blessings!

      • Thanks for your comment Erica! Many adults with T2 can potentially be misdiagnosed and are actually T1D. They way to decipher is via getting your autoantibodies tested. Have you done that? T1s have autoantibodies; T2 do not. If you’d like a free intro call with me, we can discuss further.

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    PS I did have PA who was diabetic…he knew all my excuses before I tried them and called me on my BS….then gave me great diabetic recipes to help me cope. Too bad the insurance changed my doc.

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    I am a type 1 for 25 years coming up on July 12 th. I had such trash support/ education when I was diagnosed that I was motivated to make diabetes education my career. Luckily, I was a sophomore in college when I was diagnosed and wasn’t sure what I wanted to major in anyway. Today I work as an RD, CDCES. I am very lucky that my own endo is very supportive and encouraging. Unfortunately, I have so many patients that are thoroughly depressed bc they believe that their fluctuating blood sugars are all their fault. It’s never occurred to them, or apparently their physicians either, that other factors might be at play. Majority of Physicians are reinforcing their patient’s feelings of inadequacy at controlling blood sugars by saying just don’t eat white foods or some other ridiculous band aid response. I wish I knew how to get physicians more apt to educate themselves on the many layers of blood sugar control. They sorely need it where I live.

  8. HI Karen, I’d love to set up a zoom call with you. I have online training that I’d love to get into doctor’s offices. Please visit and then scroll to the bottom of the home page and click on ‘contact’ to send me a note.

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    Dr. Jody I would love to get information about your online training for doctor’s offices you mentioned in the above post. I work as an RN CDCES at a hospital. I see a lot of patients to provide their initial education on how to self manage their diabetes as well as patients that are struggling with their management and are hospitalized with complications. I am also in the process of compiling information on the basics of diabetes management to be provided to patients in form of a booklet. There is so much information involved with self management, too much to include in a booklet form. Need to convey the most important information first then refer folks to places like TCOYD and other websites or groups where people can gain information and support. Resources such as good websites and support groups online would be greatly appreciated. FYI I am a mom to a type 1 and type 2 myself.

    • Hi Cynthia, I’d love to set up a zoom call with you. I have online training that I’d love to get into doctor’s offices. Please visit and then scroll to the bottom of the home page and click on ‘contact’ to send me a note.

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    Hi, Is there a way to print this article in larger print for my patients to read? please advise,

    • Avatar

      Hi Carolina,
      Not directly from the website, but you can copy and paste the text into a word document, and then you can make the font as large as you would like. 🙂

  11. Hello Dr. Jody, I was just wandering around on the internet when I saw your article and questions with info/answers. Delighted to read your article regarding crazy blood sugars and how other factors, besides carbs, can affect it. Two thumbs up!!! On Halloween, 10-31, I will have had T1 or as they used to call it, IDDM many years ago, for 62 years. I have gone through so many doctors and nurse educators through the years that it is hard not to develop attitudes about everything. I had one doctor just sit and watch me actively having a hypo episode right in front of her. I told aide to get me juice and doctor said no as she wanted to get a blood draw for an accurate reading first. Yes, right, just watch me fall on the floor as I was shaking so bad and sweating profusely. I had the nurse check BG with a glucometer and it was 49! Aide brought me juice and I drank it right in front of her despite her continuing to tell me “no.” I was so glad that she was just a hospital doctor and not my personal doctor. I have taken really good care of myself until other outside influences almost destroyed me. During an outpatient PT appointment, I ended up with a complete rotational fracture of my R ankle which ended up in a RBK amputation. I got pneumonia and they put me in a coma! Didn’t know why and husband wasn’t told either. Okay, while in a coma, I had a left CVA! No one told me but I figured it out as I am an occupational therapist. After out of the coma, they sent me for all these tests, in the middle of the night and destroyed both of my kidneys by using the wrong technique for a diabetic. To end this drama, I walked into the hospital with shallow breathing and left in a wheelchair, RLE amputation, unable to walk, left sided weakness, mental confusion, on dialysis as kidneys don’t function anymore, with bilateral hearing loss due to all the antibiotics and meds they were giving me, as well as a new diet kidney/dialysis restriction added to me diabetic diet. Talk about depression. I now have to learn a whole new way of living and husband has to take charge of my daily care and medication as well as my 5 MDI! Whole new life for him too. I, too, have been going through periods of dark depression as our whole lives have changed for the worse and knowing all my health issues are not just going to go away or that they are caused by mental issues. Even medication for the depression won’t erase them. I did get a kidney transplant (!) as my step son was a match! PANDEMIC hit…therefore I am stuck in the house, I think, forever as I now have no immune system, and husband is afraid to take me anywhere for fear of germs. I’ve gotten addicted to surfing the internet (found your article!) for news and just reading interesting articles. So, if you don’t mind another reader, I signed up to receive your website info! Thank you, Martha (the old one!)

    • You are a true warrior Martha! I hope that new kidney is treating you well. Blessings to you on your diabetes journey with all its ups and downs.

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