Dark kitchen, one lamp, meter beeps, number is up. You ate nothing. Welcome to the club. A fasting glucose in ketosis often reads higher than it did on carbs, and in a lean, fat-adapted person that is usually a change in fuel priority, not a disease. Two things stack. Physiological insulin resistance, where muscle stops competing for glucose because it is busy burning fat and ketones. And the dawn effect, your own hormones pushing the liver to pour sugar out before you wake. One reading diagnoses nothing. I filmed a fit physician eating 600 burgers in 30 days with bloodwork throughout, and the lesson that stuck is simple: test once and you are still guessing.
Why Does Fasting Glucose in Ketosis Read Higher Than You Expect?
Five forty in the morning, one lamp over the counter, and the meter reads higher than it ever did back when you ate bread. Here is what happened overnight: your muscles stopped bidding for glucose. That is the whole answer. Carbs go low. You run on fat and ketone bodies. Resting muscle takes up less sugar. More of it stays in the blood for the tissues that still want it. The name is physiological insulin resistance, or adaptive glucose sparing if you prefer the friendlier one. It is not the thing that rides along with type 2 diabetes. Lump the two together and the panic starts.
The evidence says the pattern may be physiological rather than pathological. Researchers in the American Journal of Physiology-Endocrinology and Metabolism argued that carbohydrate-restricted glucose intolerance resembles prolonged fasting, not automatically disease. Then a small feeding experiment in the Journal of the Endocrine Society found that restricting carbohydrate before an oral glucose tolerance test delayed glucose clearance in all participants. Which is to say: what you ate the day before is sitting inside your result.
Which brings me to the word doing all the damage. “Resistance.” It sounds like a verdict. It is a description. In my experience that single word drives more 6 a.m. panic than any number on the screen. I wrote in 600 Burgers in 30 Days that cholesterol touching 200 makes people start freaking out. Morning glucose gets the exact same treatment.
What Is the Dawn Effect, and Does Keto Cause It?
No. Keto does not cause it. The dawn effect is the early-morning glucose rise your own hormones produce, and it happens in people who have never counted a carb in their life, never owned a meter, never once thought about their liver. Keto just puts the meter in your hand. Now you see what was always there.
Bolli and colleagues watched it happen in a lab in 1984. They tracked glucose, insulin and counterregulatory hormones overnight in healthy volunteers and found a dawn-like rise initiated by an increase in glucose production, with cortisol climbing from its nocturnal low toward morning. The evidence says plumbing, not pathology — though it was lean volunteers in a lab, mechanism rather than a prediction about you.
Put the two together and the picture turns boring. Boring is good. The liver makes glucose overnight. Hormones tell it to make more around dawn. Muscle, busy burning fat, is slow to clear it. And people fixate on the morning number for one reason: the day has not touched it yet, so it feels like the truth.
Is a Single High Fasting Glucose Reading a Diagnosis?
No. One number, one morning, diagnoses nothing. The evidence says the same thing in clinical language: the American Diabetes Association’s Standards of Care state that unless there is unequivocal hyperglycemia, confirmatory testing is necessary to establish a diagnosis. Read that twice, then put the lancet down.
Because think about everything that one strip of paper cannot tell you. It cannot tell you whether the number repeats, and a confirmed result and a one-off are different animals. It cannot tell you what your average has been — across 25 randomised trials and 2,412 participants, carbohydrate restriction lowered HbA1c by 0.47% at three months and 0.36% at six, with no difference left at 12 months.
It cannot tell you what your ketones were doing, and the film shows me giving the nutritional ketosis range as 0.5 to 3.0 millimoles per litre of blood. It cannot tell you what the rest of the panel says either. At 00:13:34 the film shows Dr. Mike listing his baseline draws — CBC, thyroid hormones, inflammatory markers, vitamin and mineral panels — before a single burger. One reading, in the dark, against all of that.
What Does the Film Show About Glucose in the 600-Burger Test?
Twenty Burger King patties a day. No buns. Water only. Thirty days straight. Dr. Michael Brandon, a fit physician, with bloodwork before, during and after — and what the film shows is the testing itself, not a glucose readout on screen. At 00:13:29 he says he wants to see what kind of change happens from eating 20 burgers a day for a month.
The film suggests — that word stays — one interpretation, and it comes out of Dr. Mike’s own mouth. At the baseline draw, at 00:14:09, he predicts his inflammation panel will skyrocket. That is a physician guessing about his own body. Not a result. Whether the guess held is the last stretch of the movie.
And the protocol is the answer to the complaint about morning numbers. One draw tells you little, so we drew at four test points across three phases. We wrote up what happened to his blood and what keto and carnivore each got tested on.
What Is the Difference Between Glucose and Ketones When You Measure?
Glucose is the sugar in your blood. Ketones are the fat-derived fuel your liver builds when carbs stay low. Two readings, two stories, and ketosis is defined by the ketone number. A higher fasting glucose with solid ketones is nothing like the same glucose with none.
I ran the unflattering version of this on myself, on camera, and left it in. The film shows me driving my blood ketones down to 0.1 mmol/L at 01:29:05, taking 12 grams of exogenous ketones, waiting two and a half hours at 01:34:30, then getting a rise of 0.7 at 01:34:56. Best I hit all day was 1.1, after a dozen pricks in my finger. At 01:45:05 my urine strip read moderate, then small after a glass of water, and I say on camera it is not accurate.
What matters is that the two fuels move against each other. The evidence says so: crossover studies of ketone drinks raised blood beta-hydroxybutyrate and lowered glucose, with company-linked authors. And in the book, Dr. Dom D’Agostino supplies the floor: your glucose really doesn’t fall below three millimolar. You do not run out of sugar. You just stop needing so much of it.
How Should You Track Fasting Glucose in Ketosis Over Time?
Track the trend for weeks, next to ketones and an averaging marker. Stop re-testing the same morning hoping for a nicer answer. A direction over a month beats a decimal place on a Tuesday.
The evidence says the window matters too. A review of 23 randomised trials in 1,357 people found low-carbohydrate diets raised type 2 diabetes remission rates and improved insulin sensitivity at six months, with benefits fading by twelve. And if you are wearing a sensor, know what the thing actually reads. Continuous monitors measure glucose in the interstitial fluid under the skin and estimate the blood level, which is why a sensor and a fingerstick argue with each other during fast changes.
In my experience, the people who calm down are the ones who write the number next to what they did. The workout. The short night. The late meal. The fast. I make keto science, recipes and metabolic health work out of Functionised Productions LLC in Colts Neck Township, New Jersey, and what lands in my inbox is almost always the same thing: one scary reading, taken once, in the dark, alone.
Frequently asked questions
Does being in ketosis raise fasting blood glucose?
It can, modestly, in lean and fat-adapted people. That usually reflects glucose sparing, not disease. Researchers have argued that carbohydrate-restricted glucose intolerance resembles prolonged fasting and may be physiological. Watch the pattern over weeks instead of one figure, because one figure swings with sleep, training and last night’s dinner.
It can, modestly, in lean and fat-adapted people. That usually reflects glucose sparing, not disease. Researchers have argued that carbohydrate-restricted glucose intolerance resembles prolonged fasting and may be physiological. Watch the pattern over weeks instead of one figure, because one figure swings with sleep, training and last night’s dinner.
Will a few grams of sugar kick me out of ketosis?
Maybe. The only way to know is to measure your own blood ketones instead of arguing with yourself in the kitchen. The range I use on camera for nutritional ketosis starts at 0.5 millimoles per litre of blood. A small carbohydrate load can drop a reading under that line without undoing adaptation.
Maybe. The only way to know is to measure your own blood ketones instead of arguing with yourself in the kitchen. The range I use on camera for nutritional ketosis starts at 0.5 millimoles per litre of blood. A small carbohydrate load can drop a reading under that line without undoing adaptation.
What is blood glucose, and why does the brain need it?
Blood glucose is the sugar carried in your bloodstream and burned as a primary fuel, especially by the brain. It never vanishes, even deep in a fast. Dr. Dom D’Agostino says in the book that glucose does not fall below roughly three millimolar, and at high ketones the brain simply runs on both.
Blood glucose is the sugar carried in your bloodstream and burned as a primary fuel, especially by the brain. It never vanishes, even deep in a fast. Dr. Dom D’Agostino says in the book that glucose does not fall below roughly three millimolar, and at high ketones the brain simply runs on both.
How do you measure blood glucose at home?
A fingerstick meter gives you a point-in-time blood value. A continuous monitor gives you an estimate: it reads glucose in interstitial fluid under the skin, so it lags during rapid swings. For a months-long average, a laboratory HbA1c is the standard. Repeat testing is what turns a reading into a result.
A fingerstick meter gives you a point-in-time blood value. A continuous monitor gives you an estimate: it reads glucose in interstitial fluid under the skin, so it lags during rapid swings. For a months-long average, a laboratory HbA1c is the standard. Repeat testing is what turns a reading into a result.
The Bottom Line
A higher fasting glucose in ketosis is a question, not a verdict. Read it beside your ketones. Beside an average. Beside what you did yesterday. Then read it again on another morning. We filmed a physician eating burgers for a month with repeat draws for exactly that reason: one number cannot carry an argument. Individual results vary, and the man in the film is a fit doctor doing something deliberately extreme, not a template.
To see how the full panel behaved from baseline to the end of the burgers, rent or buy The Keto Project on Amazon Prime Video and read the prequel, 600 Burgers in 30 Days, also on Kindle and Audible. So what will you do with the number you took this morning?
Sources
- Caminhotto & Lima, Impaired glucose tolerance in low-carbohydrate diet: maybe only a physiological state (Am J Physiol Endocrinol Metab, 2013)
- Carbohydrate Intake Prior to Oral Glucose Tolerance Testing (Journal of the Endocrine Society)
- Bolli et al., Demonstration of a dawn phenomenon in normal human volunteers (Diabetes, 1984)
- Diagnosis and Classification of Diabetes: Standards of Care in Diabetes (American Diabetes Association)
- Factory-Calibrated Continuous Glucose Monitoring: How and Why It Works (PMC)
- Sainsbury et al., Effect of dietary carbohydrate restriction on glycemic control in adults with diabetes (2018)
- Goldenberg et al., Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission (2021)
- Stubbs et al., On the Metabolism of Exogenous Ketones in Humans (2017)
This article is for information only and is not medical advice. Individual results vary. Speak to a qualified clinician before changing how you eat.
The whole experiment is in the film. 600 burgers, 30 days, every blood test — and the ending we never post.
Watch The Keto Project on Amazon