Welcome to Keto Sister.  Summertime for me means that my children are sometimes at summer camp, Vacation Bible School, visiting with friends, or most often home with me.  Due to the inconsistency of their schedules, my posts have been inconsistent in recent weeks.  Forgive me! The minute school starts again, I can resume weekly posts.  Some weeks, my posts may increase to two because I have a lot to say.

Over the next two weeks, I want to discuss a topic that effects many of those who follow a ketogenic (keto) diet for different reasons: blood sugar levels.  Some encounter high or low blood sugar levels before eating keto, and it is why they decide to reduce carbs in the first place.  Others may encounter one of these after being in ketosis for a while.  Today I want to introduce a few terms to explain in laymen’s terms what blood sugar is, ideal levels, and what can happen when it is either too high or too low.


What is blood sugar and what does it tell us?

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), blood sugar is the sugar found in your blood (2017).  It comes from the food in our diets and is one of two fuel or energy sources for the body.  The body works hard to maintain homeostasis in the blood and does not like anything to be too high or too low.  When blood sugar levels are one or the other, the body works to return the level to what appears to be its preference.  Because blood sugar levels that were either lower than 81 or higher than 108 miligrams per deciliter correlate with increased risk of death (Balkau et al., 1999), this range is considered ideal for those who eat carbohydrate-based diets.  To date, I could find no scientific studies on ideal or even normal blood sugar levels among those on a ketogenic diet, though studies on human longevity and caloric restriction suggest that optimal ranges are roughly between 70 and 85 mg/dL (see Primal Body, Primal Mind by the brilliant Nora Gedgaudas for details).

Blood sugar tells us a number of things about the current state of health.  When we embark on a ketogenic diet, one of the first changes to the body is a reduction in blood glucose.  This occurs because we eat less glucose when we reduce carb levels.  The absence of carbs triggers two processes in the body simultaneously: ketone production and glucose generation.  Many functions are fueled by glucose on a normal, higher carb diet.  In the absence of those carbs, the body creates a fuel source from dietary fat and stored fat called ketone bodies, and it fuels as many processes with ketones as it can (hence, ketosis).  Some things do require glucose for fuel, such as red blood cells, the thyroid, insulin mechanisms in muscle and fat cells, mucin production, and the brain.  For these, the body creates the glucose it needs from either triglyceride or protein through a process called gluconeogenesis.  This process, despite opinions to the contrary, occurs in the body based upon the body’s need for glucose and is not a supply driven process (meaning it is not based upon how much fat or protein you eat).

When blood sugar levels are 80 mg/dL or lower, one is considered to have low blood sugar.  Because ketones are being utilized in a healthy body during nutritional ketosis, lower blood sugar levels may be considered an ideal state (Manninen, 2004).  It demonstrates that the body is maintaining minimum glucose levels because higher levels are no longer required for fuel.  One reason this is considered ideal is because elevated blood glucose levels can be toxic to the body.  The opposite problem, high blood sugar, is much more common among Americans in particular.  The body maintains homeostasis in blood glucose levels because elevated levels lead to problematic bodily functions with the kidneys, eyes, nerves, and feet (NIDDK, 2017).  When levels are too high, it means that the body is not responding to its mechanism for transporting glucose out of the blood and into cells for storage.  This lack of sensitivity to insulin is called insulin resistance.


Blood Glucose and Insulin

Insulin resistance is a condition often created by eating too many carbs.  When we eat carbs and proteins, glucose is transported from the stomach into the bloodstream.  The blood carries the glucose around the body for uptake and use, and the excess is removed for storage when insulin is released.  If a person eats too many carbs and frequently has insulin released, it is possible for the body to develop an insensitivity and stop responding to the same amounts.  It is kind of like a mother who nags her daughter (I can certainly relate to this analogy!).  Over time, the child will tune out nagging and the parent may feel that raising her voice will encourage responsiveness.  So she yells, and the daughter listens until eventually she does not even respond to yelling because her mother yells all the time.  The louder mom yells, the more the daughter resists.  In the body, sometimes the more insulin released, the less the body responds (insulin resistance).  Or sometimes the body has an exaggerated response and drops blood glucose levels too low (reactive hypoglycemia), which can be just as debilitating with symptoms of dizziness, fatigue, weakness, blurry vision, fainting and more.

Very high or very low blood glucose levels are dangerous, especially for those with diabetes.  For this reason, many with issues regulating their blood sugar levels find they are better able to stabilize blood sugar on a lower carb diet.  Without the dietary fluctuations of glucose, the body takes on more responsibility for maintaining glucose within range.

Why, then, would a person have elevated blood sugar in ketosis?  Assuming a person is eating a reduced carb diet and does not have insulin resistance as described above, two reasons come to mind:

  1. Physiological Insulin Resistance, also known as PhIR, can be induced in a body that does not have enough glucose available for all the functions needed.  To ensure that enough glucose stays available for the brain, the rest of the body is signaled to resist insulin and leave available glucose in the blood for the brain's use only.
  2. Elevated cortisol, which is a heightened stress response in which the body creates glucose in the liver in response to emergency signals that glucose is needed.


Both of these states are common in ketosis, but they are not healthy or ideal.  In next week’s post, I will explain these states in greater detail and outline why they are problematic, the circumstances under which they occur, and how to resolve them if they happen to you.  If you have any questions, please post your comment below.  Be sure to return next week—thanks for reading.



Balkau B et al. (1999).  Is There a Glycemic Threshold for Mortality Risk?  Diabetes Care 22 (5), 696-699.

Manninen, A. H. (2004). Metabolic Effects of the Very-Low-Carbohydrate Diets: Misunderstood “Villains” of Human Metabolism. Journal of the International Society of Sports Nutrition1(2), 7–11. http://doi.org/10.1186/1550-2783-1-2-7

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) (2017).  Blood Sugar.  National Institutes of Health, US National Library of Medicine. https://medlineplus.gov/diabetescomplications.html