Reducing dietary carbohydrates to resolve chronic low blood sugar may seem counter-intuitive, but for people with dysregulated insulin production or insulin resistance, low-carbohydrate diets like the ketogenic diet may be the most effective choice for preventing hypoglycemic attacks. I struggled with chronic reactive hypoglycemia (low blood sugar after meals) for years until I started the keto diet in 2020. This change has been transformative for me and many others struggling with unstable blood sugar. In this article, I explain the science of why post-meal hypoglycemia occurs, what steps I’ve taken to prevent it from happening, and how I’ve made a ketogenic diet a sustainable choice for myself. If you’ve struggle with hypoglycemia and blood sugar imbalances like me, the ketogenic diet could be a great solution for reclaiming your health.
 
What is Reactive Hypoglycemia?
Reactive hypoglycemia occurs when a person experiences an abnormally high peak in blood sugar after a carbohydrate-containing meal and a subsequent steep drop in blood sugar one to three hours later, without injecting insulin. This is sometimes called “postprandial” or “spontaneous” hypoglycemia. It’s a different kind of hypoglycemia than that caused by injecting too much insulin or using other blood-sugar-lowering medications (called “iatrogenic hypoglycemia”).
 
In reactive hypoglycemia, the body responds to a spike in blood sugar above normal levels (that is, above around 120 mg/dL) by over-producing insulin from the pancreas, or producing insulin too late. This causes a sudden drop below a healthy level one to three hours later. Hypoglycemia is generally defined as having less that 70 mg/dL of a sugar called glucose circulating in the blood, though symptoms can occur at levels higher or lower than this. A sudden crash in blood sugar can cause jitters, light-headedness, strong thirst or hunger, confusion, anxiety, weakness, sweating, and if severe enough, unconsciousness, coma, or death. Reactive hypoglycemia is a common occurrence in people with type 2 diabetes, cystic fibrosis-related diabetes, metabolic syndrome, insulin resistance, glucose intolerance, or generalized “hypoglycemia”. It rarely happens in type 1 diabetes, because in type 1 the endocrine pancreas is unable to produce any insulin at all. Unfortunately, reactive hypoglycemia is poorly studied or understood, and conventional treatment methods are often unsuccessful.
 
My Journey with Blood Sugar Dysregulation
For over fifteen years I’ve been struggling with reactive hypoglycemia, a complication of my genetic disease, cystic fibrosis. Over the years it had slowly worsened, especially after I was diagnosed with diabetes in 2013. In the beginning, I only experienced hypoglycemic crashes mid-morning, one or two hours after eating breakfast. I noticed that I was especially likely to crash if I ate sugary or high-carb breakfasts, so I gradually reduced the amount of carbohydrates I ate in the morning to prevent my blood glucose from spiking. Around 2017, I started a low-carbohydrate version of the Paleo diet, keeping daily carbohydrates under about 80g. This was effective for a while, but I was also pretty loosey-goosey with it and continued to experience both hyperglycemia and hypoglycemic attacks every few days.
 
Then, in early 2020, my reactive hypoglycemia became uncontrollable after a medication change. I was experiencing crashes daily, sometimes three or four times a day. These crashes could get critically low (as low as 30 mg/dL). I started using a continuous glucose monitor (CGM), but my blood sugar was so unstable that the CGM was not reading accurately, and so I had to finger-stick test with a glucometer around ten times per day. I especially worried about having a critical low (that is, below 55 mg/dL) while asleep… and never waking up. I literally feared for my life every day.

This whole situation gave me constant anxiety and insomnia. I dove deep into the scientific literature on the endocrine system and started experimenting. As a nutritionist and clinical herbalist, I used every tool I knew of to help me balance my blood sugar. Some of it helped a little, but none of it was enough to stop the crashes from happening. Worst of all, when I experienced a crash I would often over-correct with more carbs than I needed, which would set up the next crash a few hours later. It was a terrifying rollercoaster, and I couldn’t get off the ride.
 
In October of 2020, I was coming to my wits end. My doctors couldn’t help me. They’d just tell me to inject more insulin with meals, and then ignore me (or shrug) when I told them that would only make my crashes worse. It was at this moment that I finally decided to try what I considered to be the option of last resort: the ketogenic diet.
 
Two and a half years later, I’m still keto and my blood sugar is more stable than ever. My chronic anxiety is gone, I can sleep through the night without concern, and I can exercise without having to stop and eat half-way through. My hemoglobin A1c has also significantly improved, from its peak at 6.5% in 2013 down to 5.1% in January 2023. I no longer use insulin at all – my blood sugar is entirely controlled by diet and exercise. This last part is unique to my particular case, as my pancreas still produces its own insulin (however improperly). Some people with blood sugar imbalances or diabetes will need to use insulin or other medications for the rest of their lives, even if they use a keto diet, and that’s perfectly ok. The goal is not to be insulin- or medication-free – the goal is to have steady blood sugar so that we can stay safe, feel healthy, and get on with the rest of our lives.
 
What Causes Reactive Hypoglycemia?
Reactive hypoglycemia can be understood as a mismatch between the amount of insulin produced by the pancreas and the amount of glucose circulating in the blood. Insulin is a hormone that the pancreas produces to move glucose out of the blood and into the tissues, where it’s used as energy for cellular activity. Normally, when we eat, the body immediately detects how much carbohydrate we ingested and produces the exact right amount of insulin on-demand. The pancreas also produces a small amount of basal insulin throughout the day unassociated with meals.
 
For people with blood sugar disorders, several things can contribute to hypoglycemia. The pancreas might produce roughly the right amount of insulin, but the release might be delayed. A delay would mean that by the time the insulin begins to push the glucose out of the bloodstream, small amounts of basal insulin or physical activity might have reduced the blood sugar already, so that when the insulin kicks in, it overshoots the body’s need, eventually causing a drop below 70 mg/dL. In addition, the body may be unable to properly detect how much carbohydrate was just eaten, preventing the pancreas from judging the right amount of insulin to produce [1,2,3].
 
People with healthy endocrine systems might also experience occasional, non-critical hypoglycemia, but it is usually transient and self-correcting, even without food. The pancreatic hormone glucagon acts as a counter-balance to insulin, so if hypoglycemia does occur, the pancreas releases glucagon which raises the blood sugar back to healthy levels. In some people with blood sugar disorders, the pancreas does not produce glucagon properly. Failed release of glucagon occurs in reactive hypoglycemia, so the only way to correct it is to eat carbohydrates or inject exogenous glucagon.
 
There may be other causes to hypoglycemia unique to certain disorders or diseases including insulin resistance, pancreatic tumors, liver disease, and so on. The suitability of the ketogenic diet must be judged on a case by case basis according to one’s individual diagnoses and symptoms, ideally in consultation with a knowledgeable healthcare practitioner.
 
Why Choose Keto for Addressing Hypoglycemia?
The primary reason keto is a great choice for those of us with blood sugar imbalances is that by eating fewer carbohydrates we prevent spikes in blood sugar, minimize insulin secretion, and prevent post-meal crashes. Reducing insulin secretion helps us avoid an insulin overshoot and excessive drop in blood sugar.
 
By reducing carbohydrate intake to a total of around 20-60 grams per day (tailored to one’s individual needs) our tissues learn how to gain energy from ketones rather than glucose. Ketones are small molecules produced by the liver from the breakdown of fats. Ketones are normally produced during fasting and other times when dietary carbohydrates are unavailable. Ketosis is a physiological state in which the body produces and is fueled primarily by ketones. Nutritional ketosis is a natural adaptation which allows for metabolic flexibility when food sources shift or become scarce. In fact, ketones are the preferred fuel of the vital organs such as the kidneys, heart, and brain. Studies have shown that nutritional ketosis can improve many neurological conditions including epilepsy, Parkinson’s, migraines, Alzheimer’s
, and depression [4]. 
 
The transition to ketosis doesn’t happen overnight. The conversion can take weeks or months, depending on the individual’s physiology and how strictly they adhere to the diet. Not everyone needs to monitor their ketone levels with urine strips or a blood ketone meter, but for those of us with unstable blood sugar, it may be a good idea to do so. This can help us know if our diets are adequately producing enough ketones to keep the blood sugar steady. I aim for a blood ketone level of 1.0 to 2.0 mmol/L, though I don’t test every day.
 
Being in ketosis means that I can eat less frequently and am hungry less often, but I don’t usually skimp on calories. Even though I rarely have crashes anymore, I still keep a little tube of maple sugar cubes with me when I exercise, just in case. I’ve discovered that a half-cube (amounting to about 3g of sugar) is enough to rescue me from most hypoglycemic episodes. Sometimes, if I poorly time post-meal exercise, I can slide into a mild hypoglycemia which is easy to correct with a small amount of maple sugar.
 
Another benefit of ketosis is that it’s inherently anti-inflammatory [5]. Paired with a whole foods diet including low-carb vegetables, grass-fed and pasture-raised animal products, and small amounts of nuts, the keto diet is a great choice for reducing systemic inflammation, which in turn improves insulin resistance.
 

Getting Started
We’re using the ketogenic diet as a therapeutic medical intervention, therefore it’s important to approach it with caution and adequate planning. Do your research before starting (see resources listed below). Inform your medical practitioners you’ll be trying something new with your diet, and develop ways to track your progress and record what works and what doesn’t. I’ll be honest with you, the beginning can be a little tough, most especially because it requires some experimentation as you learn more about your body’s particular needs. There is no one-size-fits-all approach to going keto, but I can offer some tips based on my own mistakes and successes:

1. Don’t go cold turkey. For those of us with unstable blood sugar, we need to slowly retrain the pancreas to produce less insulin. Launching in too fast can result in steeper crashes. For several weeks after dropping my carb intake to 60g per day, my pancreas was still overproducing insulin daily. This was frustrating, but I persisted. It took about two months for the blood sugar to get steady enough that I felt safe to drop the carbs further. At this point my hypoglycemic crashes reduced from three per day to once every other day. Now, two and a half years later, if I keep strict to my carb limit of about 40-50g per day I get a mild hypoglycemia only once or twice every couple of weeks. Based on my experience, the safest first step is to drop carbs to about 75g per day. In two weeks consider reducing carbs by another 10g. In another two weeks drop an additional 10g, and so on until you find your body’s ideal carb limit. Base this limit on your symptoms and ketone production. For me, I get adequate ketone production, fiber intake, and blood sugar stability with 50g per day, though some days I allow up to 60g, mostly from additional vegetable fiber.
2. “Net carbs” is a marketing gimmick. The standard medical approach to using a ketogenic diet is to count total daily carbohydrates – fiber, sugars, starches, and all.
3. In the first several weeks, find a source of high-fiber “baseline” carbohydrate to provide a steady supply of glucose without spiking the blood sugar. For me that was “peas pudding”, or boiled split peas made into a mash. I always kept this in the fridge and ate 1-2 tablespoon of it every few hours in the beginning. Alternatives are small amounts of hummus, oatmeal (unsweetened – I like it with butter and salt), and unsweetened sunflower seed or nut butter. As my insulin secretion re-regulated, I reduced this baseline carb source and then eliminated it entirely.
4. Minimize or eliminate “cheat days”, especially at the beginning. For those of us with blood sugar instability, having a cheat day can be pretty risky. Remember that we’re re-training our body to shift to a different fuel source, so consistency is key. Several months after achieving more blood sugar stability, it may be ok to have 10-20g more carbs on occasion, but beware of making this a regular occurrence or the pancreas may return to its old habits.
5. Avoid carbs in the morning. This was one of the earliest and most important rules I learned, as reactive hypoglycemia occurs most easily after breakfast. Carbs absorb much quicker after a prolonged fast, leading to a spike in blood sugar. I’ve found it best to limit carbs to less than 10g at the first meal of the day – the lower the better. Instead, I choose a high-protein and high-fat breakfast.
6. Limit per-meal intake of carbs to a maximum of 20g. Per-meal limitations are just as important as daily total restrictions for maintaining steady blood sugar. Also, I make sure that my carbs consist mainly of fiber from vegetables or nuts/seeds. Getting our daily carb allotment mostly from simple sugars is not going to help balance our blood sugar very well.
7. Add medium chain triglycerides (a.k.a. MCT oil) from coconuts to your meals. Adding MCT oil to your diet can boost ketone production significantly, which can help speed up the transition to ketosis. This may be especially useful in the evening as we prepare for the overnight fast. If your budget doesn’t have room for MCT oil, regular coconut oil is nearly as effective.
8. We don’t need to buy fancy “keto-friendly” bars, snack foods, or expensive supplements. Now that keto has become a fashionable diet, it’s easy to get sucked into the consumerism around it. Packaged keto products are often expensive, wasteful, and have hidden ingredients that may throw off our blood sugar. The base of our diet should be whole foods, ideally grown and raised locally using environmentally-sustainable and humane methods.
9. Ensure adequate electrolyte intake. You may have heard of the phenomenon called “keto flu” some people experience at the beginning of a keto diet. Symptoms may include fatigue, muscle weakness, and generally feeling lousy. Many keto experts suggest this is the result of inadequate electrolyte intake. I never experienced this personally, perhaps because my diet transition was slow, but it may be a good idea to take a sugar-free electrolyte supplement daily for the first few weeks.
10. Take a short walk after eating a meal containing carbs. Because exercising muscle can suck up glucose from the blood without the need for insulin, exercise can be a very effective tool for preventing hyperglycemia after a meal. I recommend gentle exercise like walking. If the meal contains more than 20g of carbs, more rigorous exercise may be warranted. Exercise immediately after eating. I discovered that waiting even ten minutes could allow the blood sugar to rise enough that the pancreas detects it and produces insulin before I could cut off the peak through walking. Exercising after the pancreas has already produced a large bolus of insulin can risk steepening a post-meal drop in blood sugar.
11. Find the minimum effective rescue dose of carbs needed to correct a crash. It can feel scary to be hypo and that rush of adrenaline may encourage us to eat too many carbs to correct it. Overdosing on corrective carbs can lead to hyperglycemia and set up the next crash. So it may take a little experimentation to find the right dose for you. For me, most of the time it requires only 3g of a sugar source like maple sugar candy or honey (I avoid glucose tablets due to their artificial colors and flavors). On occasion I may need to double that dose. When I get hypo it’s almost always on a hike, so I make sure to rest for at least 5 min after dosing to let it sink into the blood stream faster. I test again about 10 min after dosing, and if I’m still not above at least 70 mg/dL, I dose again. I keep a small tube of rescue carbs with me at all times.
12. Eat plenty of fat. Remember that a keto diet is first and foremost a high-fat diet. The body uses fats to create ketones, allowing us to get our energy primarily from fat instead of carbs. Personally, I get about 60% of my daily calories from fat. We must also pay attention to the quality of our dietary fats. Grass-fed butter or ghee, unfiltered coconut oil, and extra virgin single-sourced olive oil are a few of the best choices. Avoid refined polyunsaturated oils like soybean, corn, canola, peanut, or generic “vegetable” oil. Similarly, margarine and transfats are highly inflammatory and contribute to cardiovascular disease. Cold-pressed flaxseed and sustainable fish oils are great choices to get in those anti-inflammatory omega-3 fatty acids. Grass-fed and pasture-raised meats, dairy, and eggs are excellent sources of healthy fats, as is sustainable wild-caught seafood.

 
Not ready yet to commit to keto?
For those not yet ready to commit to the keto diet, it may be good to spend some time doing research and practicing a few of the tips I outline above. In particular, I think tips number five, six, ten, and eleven are the most important for anyone wanting better blood sugar control. These steps will help even if you’re not following a strict low-carb diet. Experimenting with these steps first can help build the willpower needed to start and stick with a keto diet.
 
In addition, I recommend paying attention to your stress level. Both physical and psychological stress release cortisol, a stress hormone which contributes to insulin resistance and unstable blood sugar. Mindfulness, deep breathing, rest, and good sleep hygiene are very important for blood glucose regulation. Also consider cutting out sugar and experimenting with using a low-carb sweetener like whole-leaf stevia powder. Read up on the glycemic index and cut out refined carbs (like white flour) and other foods which spike blood sugar more quickly. Lastly, cinnamon bark (as powder, tincture, capsule, tea, or added to food) has been used for thousands of years to stabilize blood sugar, and studies have shown it to be effective at slowing the rate of carbohydrate absorption and improving insulin sensitivity.

 
I hope this article has been helpful for you to understand more about why reactive hypoglycemia happens and what steps you can take to address it. There are many great resources out there to learn more about ketosis and the keto diet. Here’s a video introduction to the ketogenic diet by Dr. Dominic D’Agostino. He runs a helpful website with lots of scientific information and tips on the keto diet, including an excellent list of books, apps, and other resources to get started. If you’re interested in the science of ketosis, here’s a short article on its basic metabolic pathways. I’ve found Thomas DeLauer’s Youtube channel to be a rich resource of practical guidance on ketosis and intermittent fasting. I also appreciate the research of Dr. Peter Attia, an expert on ketosis who runs a great blog and podcast on the science of ketosis and fasting.
 
There is much more to say on this topic, so if you’d like me to write about any  of the above topics in greater detail, please leave a comment below. If you have used a low-carb or ketogenic diet to balance your blood sugar, please tell us about your experiences and insights!
 
Thank you for reading. I wish you success in your healing journey.
 
 
 
References:
[1] Hicks, R., Marks, B. E., Oxman, R., & Moheet, A. (2021). Spontaneous and iatrogenic hypoglycemia in cystic fibrosis. Journal of Clinical & Translational Endocrinology, 26, 100267.
[2] Battezzati, A., Mari, A., Zazzeron, L., Alicandro, G., Claut, L., Battezzati, P. M., & Colombo, C. (2011). Identification of insulin secretory defects and insulin resistance during oral glucose tolerance test in a cohort of cystic fibrosis patients. European journal of endocrinology, 165(1), 69.
[3] Kandaswamy, L., Raghavan, R., & Pappachan, J. M. (2016). Spontaneous hypoglycemia: diagnostic evaluation and management. Endocrine, 53(1), 47-57.
[4] McDonald, T. J., & Cervenka, M. C. (2018). Ketogenic diets for adult neurological disorders. Neurotherapeutics, 15(4), 1018-1031.
[5] Pinto, A., Bonucci, A., Maggi, E., Corsi, M., & Businaro, R. (2018). Anti-oxidant and anti-inflammatory activity of ketogenic diet: new perspectives for neuroprotection in Alzheimer’s disease. Antioxidants, 7(5), 63.

In October 2020 I began a very successful experiment with the ketogenic diet to control my  reactive hypoglycemia. I wrote this post in April 2021 outlining the initial phases of this experiment. Since then, a lot has changed, so I wanted to give an update on how it's working for me now.

Even though I had been "keto" for a year and a half, I had been pretty loosey-goosey with my carb limits. As long as I stuck under 60g carbs/day I could see that I was producing a little bit of ketones (using a ketone meter) and this kept my glucose relatively stable. After a few months of keto, my A1c dropped dramatically from 6.2 down to 5.2. I'm holding steady now at around 5.3.

But because I was a little lax with my carbs, especially between the end of 2021 and the beginning of 2022, I would regularly get hypoglycemic crashes once every couple of weeks which I required a rescue remedy (a half of a cube of maple sugar). So recently I've gotten much more strict with my carb intake, and the results have been excellent. My ketones are in optimal range almost all the time, my energy and digestion is great, and my blood sugar is in better control than ever before.

As a person struggling with CF-related diabetes, I've tried lots of things to balance my blood sugar over the years. It wasn't until 2020 when I discovered the ketogenic diet that my life really changed for the better and my blood sugar came under excellent control. Diet is the primary intervention for controlling most types of diabetes, but sometimes we may need medications and/or herbal medicines to assist with glucose control. 

I recently taught an in-depth class on holistic nutrition and herbal medicine for diabetes and blood sugar imbalances including CFRD, types I and II diabetes, metabolic syndrome, reactive hypoglycemia, and glucose intolerance (which you can check out here). I cover the topics of diet and herbs very comprehensively in that class, but in this article I'll mention briefly a few medicinal herbs that I have used and recommended to other diabetics to assist with blood sugar control. 

For the last ten years or so I've struggled with reactive hypoglycemia related to CFRD (cystic fibrosis-related diabetes). In the last couple of years it has become very difficult to manage. Reactive hypoglycemia is a condition where the blood sugar crashes 1-3 hours after a meal containing carbohydrates, leading to distressing hypoglycemia symptoms such as shakiness, anxiety, weakness, brain fog, fatigue, tachycardia, and in severe cases, unconsciousness or even coma. Reactive hypoglycemia is more common in CFRD than many CF-specialists realize. Despite avoiding simple carbohydrates and adhering to a Paleo-ish diet for many years, my reactive hypoglycemia has only gotten worse. That is, until I started a ketogenic diet in October of 2020. I've made a remarkable improvement in my blood sugar control and I'd like to report my success in detail here.