What are optimal blood glucose level for ketosis?

  • Elevated insulin and blood glucose levels are associated with a wide range of health issues including obesity, mental health, cancer, cardiovascular disease, and stroke.
  • “Normal” blood sugars are not necessarily optimal for long-term health.
  • Most people are somewhere on the spectrum between optimal blood sugars and full-blown Type 2 Diabetes.
  • Maintaining blood sugars closer to optimum levels is possibly the most important thing you can do to manage your health, reduce body fat and slow ageing.
  • Blood ketones tend to rise as blood glucose levels decrease, though they can vary depending on a number of factors.
  • People who are physically fit and/or who have been following a ketogenic lifestyle for a long period do not tend to show very high blood ketone levels.

what is diabetes and why it matters?

“Diabetes” refers to a group of metabolic diseases where a person has high blood sugars over an extended period of time.

Diabetes is expensive.  In 2012 it cost the US a quarter of a trillion dollars in hospital costs and lost productivity and the cost of “diabesity” is forecast to triple by 2050 grow and become a major burden on our economy.  Diabesity has even been classed as a matter of economic and national security (Pompkin, 2013).

One in twelve people are considered to have Type 2 diabetes, however, forty per cent of the US population is considered to be “pre-diabetic” and this number is forecast to grow by more than half over the next two decades to 592 million people by 2035.  If you have prediabetes you have a one in two chance of progressing to Type 2 Diabetes within five years.

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The generally accepted diagnosis levels for prediabetes and Type 2 Diabetes are shown in the table below.




after meal


% pop







< 100

< 5.6

< 140

< 7.8

< 6.0%


pre-diabetic 100 – 126

5.6 to 7.0

140 to 200 7.8 to 11.1



type 2 diabetic

> 126

> 7.0

> 200

> 11.1

> 6.4%


However, while the diagnostic criteria defines half the population currently as ‘normal’, normal is far from optimal.

what are the risks of high blood sugars?

The Hba1c [7] is a test that gives an indication of your average blood sugar over the past three months.  While half the western population has an Hba1c of greater than 6.0% and hence is considered to have prediabetes or full-blown Type 2 Diabetes, the risks of stroke, heart disease and death from any cause start at much lower levels.


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Increasing HbA1c is associated with an increased risk of cancer.


Your risk of cardiovascular disease, coronary heart disease and stroke all increase with HbA1c.  And anti-diabetic medications, even though they reduce your blood glucose levels, don’t help reduce your risk.


You have a much better chance of delaying the most common diseases of ageing if you have an Hba1c of less than 5.0%.  Keeping your blood sugar under control is possibly the most important thing you can do to manage your health, manage body fat, gut health, reduce your risk of cancer and slow ageing, regardless of whether you have been formally diagnosed with diabetes.

what are optimal blood sugars?

You can use your average blood sugar values from a home blood glucose metre to see how you’re tracking compared to optimal.

Paul Jaminet notes that the optimal range for blood sugar is between 70 and 100mg/dL (3.9mg/dL and 5.6mmol/L). Doctor Richard Bernstein recommends an ideal blood sugar of 83mg/dL (or 4.6mmol/L) for Type 1 Diabetics.

The conversion between HbA1c and average blood sugar is shown in the table below. The “risk levels” are based on cardiovascular disease and stroke data above.

risk level HbA1c average blood sugar
 (%)  (mmol/L)  (mg/dL)
optimal 4.5 4.6 83
excellent < 5.0 < 5.4 < 97
good < 5.4 < 6.0 < 108
danger > 6.5 > 7.8 > 140

By the time you become “pre-diabetic” with an HbA1c greater than 6.0% you’re well into the danger zone and it’s likely that your pancreas has been pumping out high amounts of insulin trying to keep up for some time and you are well and losing the battle of metabolic health.  If you’re exposed to modern processed foods then it’s likely that you are somewhere on the spectrum between optimal and full-blown diabetes. [16]

What are optimal ketone levels?

Once you get your head around blood glucose you may come across the ketogenic diet and managing blood ketone levels.  High blood ketone levels are dangerous in someone with Type 1 Diabetes when they have no insulin and very high blood glucose and ketones at the same time (i.e. ketoacidosis).  However lower blood ketones with healthy blood sugars are a sign that you have a good balance between your fat burning and glucose burning metabolisms.

The chart below shows how glucose and ketone values are related different people with different levels of metabolic health.  In someone with full-blown Type 2 Diabetes their blood sugars and insulin levels are high and they struggle to release ketones and body fat stores when they don’t eat so they are driven to eat again.  By contrast, someone who is metabolically healthy has low glucose and insulin levels and will more easily be able to go long periods without food as their body fat stores can be released easily.

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To look at this another way, the chart below shows two thousand glucose and ketone values from numerous people following a low carb lifestyle.  Most people maintain the sum of their blood glucose and ketone levels (i.e. total energy) at around 6.0mmol/L.  If you’re on the left-hand side of this chart with a lower total energy level you will be pulling stored energy from your body (i.e. endogenous ketosis).  However, if your total energy is high (e.g. due to large amounts of refined fats or exogenous ketones) your body will likely be secreting extra insulin to bring the excess energy out of your bloodstream back into your body fat stores.


Someone who is metabolically healthy will tend to run at a lower total energy because they can more easily mobilise their stored energy when required.  Think of one of our ancestors hiding in a cave.  There is no point in having high levels of energy floating around in his bloodstream all the time (unused glucose in the blood becomes glycated and unused cholesterol becomes oxidised).  But when required they can quickly mobilise the energy to run away from whatever wanted to eat them.

Image result for caveman running from dinosaur

The table below shows the ketones corresponding to the different levels of metabolic health, HbA1c, blood ketones and the glucose : ketone index.

 metabolic health HbA1c average blood glucose blood ketones GKI
 (%)  (mmol/L)  (mg/dL)  (mmol/L)
low normal 4.1 3.9 70 > 0.3 1.9
optimal 4.5 4.6 83 > 0.3 3.5
excellent < 5.0 < 5.4 < 97 > 0.3 11
good < 5.4 < 6 < 108 < 0.3 30
danger > 6.5 7.8 > 140 < 0.3 39

If you’re an athlete or have been following a low carb diet for a while your blood ketone levels may be lower.   Unless you’re chasing therapeutic ketosis there is no need to add extra dietary fat to achieve higher ketone levels, particularly if your goal is fat loss from your body.

how to optimise your blood sugars?

There are a number of things you can do to reduce your HbA1c, improve your insulin sensitivity and reduce your total energy including:

Large doses of highly insulinogenic foods require high doses of insulin to normalise blood glucose.   The continuous glucose monitor plot below shows the blood sugar roller coaster experienced by a Type 1 Diabetic on a normal western diet.  This style of blood sugar fluctuation occurs to some extents in all of us to some degree, depending on our diet and our insulin sensitivity.

image004 - Copy (2)

Through the use of a low insulin load dietary approach, even someone with Type 1 Diabetes can achieve normal healthy blood glucose levels without resorting to mega doses of insulin.  Even if you are do not have diabetes you can use a low insulin load diet to optimise your blood glucose levels.

food lists optimised to suit your goal

The table below has been designed to help you choose the dietary approach that is most appropriate for you based on your weight loss goals and glucose levels.  As your blood glucose levels under control with a lower insulin load diet, you can then start to focus on more nutrient-dense foods which will help eliminate processed junk foods and help you to be satiated with less food.


average glucose

waist : height


therapeutic ketosis

> 140

> 7.8

diabetes and nutritional ketosis

108 to 140

6.0 to 7.8

weight loss (insulin resistant)

100 to 108

5.4 to 6.0

> 0.5

weight loss (insulin sensitive)

< 97

< 5.4

> 0.5

< 97

< 5.4

< 0.5

nutrient dense maintenance

< 97

< 5.4

< 0.5

post updated: December 2017


[1] http://www.dailymail.co.uk/health/article-2997882/Diabetes-epidemic-400-million-sufferers-worldwide-Number-condition-set-soar-55-20-years-unless-humans-change-way-eat-exercise.html

[2] http://en.wikipedia.org/wiki/Diabetes_mellitus_type_1

[3] http://www.drperlmutter.com/

[4] http://www.primalbody-primalmind.com/about-nora-gedgaudas/

[5] http://drrosedale.com/#axzz3TzvVehTb

[6] http://www.wheatbellyblog.com/

[7] http://www.diabetes.co.uk/what-is-hba1c.html

[8] http://www.amazon.com/Grain-Brain-Surprising-Sugar-Your-Killers/dp/031623480X

[9] http://www.drperlmutter.com/important-blood-test/

[10] http://www.cardiab.com/content/12/1/164

[11] http://freetheanimal.com/2009/02/sugar-feeds-cancer.html

[12] http://chriskresser.com/how-to-prevent-diabetes-and-heart-disease-for-16

[13] http://www.drperlmutter.com/important-blood-test/

[14] http://care.diabetesjournals.org/content/36/4/1033.full

[15] http://www.ebay.com.au/itm/like/251841014229?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=107&chn=ps

[16] https://vimeo.com/52872503

[17] https://www.youtube.com/watch?v=zJGAbZIvRh8

[18] http://perfecthealthdiet.com/2011/11/safe-starches-symposium-dr-ron-rosedale/

[19] http://www.primalbody-primalmind.com/

[20] http://www.dietdoctor.com/lose-weight-by-achieving-optimal-ketosis

[21] https://www.youtube.com/watch?v=Yo3TRbkIrow

[22]  http://www.cardiothoracicsurgery.org/content/3/1/63

post updated: 22 March 2021

41 thoughts on “What are optimal blood glucose level for ketosis?”

  1. Is “average blood sugar” calculated by averaging your fasting blood glucose measurements, or do you include postprandial values too?

    • HbA1c is an approximation of average blood sugars over the last three months.
      So if you’re trying to estimate your HbA1c use all your blood sugar data, both fasting and after meals.

      • Your chart shows excellent metabolic health with HbA1c <5.0 and average blood sugar <97 YET my last blood test shows fasting blood sugar of 89 with HbA1C of 5.5.

        Is there an answer for this seeing discordance?

  2. I love your focus on insulin, as I also believe that it is more important than glucose response. However, I would be interested in your opinion of resistant starch, a specific type of dietary fiber that ferments in the large intestine and directly improves insulin sensitivity. Wouldn’t that be more like treating the cause instead of avoiding the symptoms?

    See http://www.resistantstarch.us/health benefits/blood-sugar-benefits/ for the data. We are expecting the United States Food and Drug Administration to rule on a health claim petition that resistant starch helps reduce the risk of type 2 diabetes because it improves insulin sensitivity, especially in individuals with prediabetes. (https://www.regulations.gov/#!docketDetail;D=FDA-2015-Q-2352)

    Not all types of dietary fibers do this. For instance, the cellulose from plant cell walls is a bulking fiber, but is minimally fermented and does not have these effects. The resistant starch information fits with your data, as green bananas, beans, lentils, and unprocessed grains are all rich in resistant starch.

  3. No, there are not. The vast majority of the studies used digestible starch as the control. Researchers try to limit the variables in studies so they can draw conclusions from the differences in results.

    A diet with a wide variety of non-starch veggies would contain a little resistant starch but there isn’t way to guess how they would compare.

    I guess I fall back on the fact that starch has always been in human diets so it naturally evolved as a major food for our microbiota.

    • I’ve got a friend who has just found she has pre-diabetes and has started testing her blood sugars. After meat, veg and potato her blood glucose was 9.0mmol/L. Without the potato, same meal her blood sugar is 5.3mmol/L (my wife with type 1 has a similar but more exaggerated experience). Should they eat more or less potato?

  4. Thank you so much for this blog and the effort you put in to helping others!!! I am type 1 32 years and finding it very hard to gain control over bs levels. Read Dr B’s book and trying to put it all together to gain control. I have been eating lc for 1.5 years and am gaining weight and taking about 42 units a day. On a pump and dex I am going to try using the insulin load to see if it can help. Thank you for all your information

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