A Guide to Optimal Blood Glucose Level for Ketosis

Mehdi Yacoubi
Mehdi Yacoubi
July 22, 2021
A Guide to Optimal Blood Glucose Level for Ketosis

If you’re on a ketogenic diet, one way to measure success is by tracking and maintaining specific blood glucose levels and ketone levels.

Up until a few years ago, tracking blood sugar levels was reserved for those with diabetes or pre-diabetes, but as we continue to learn more about the importance of balanced blood sugar levels for general health, it has become more mainstream, especially in the keto community. 

It has become popular in this community because it’s important to maintain an optimal blood glucose level for ketosis. When it comes to the high-fat, high-protein, low-carb diet, the goal is to keep carbohydrates low, which helps blood sugar stay low. 

Opposingly, if your blood sugar levels are frequently increasing, your body will be unable to stay in ketosis, which is the primary objective for those on a ketogenic diet.

We’ll look at what ketosis is, how to test your blood sugar and ketone levels, and how to use the data to measure success.

The Keto Diet and Ketosis

A ketogenic diet involves eating high-fat, low-carbohydrate food in order to reach ketosis. Most people who start the diet are looking for results like weight loss, reversing insulin sensitivity (metabolic syndrome), and more. 

Ketosis is a temporary state where your body switches its energy source from glucose to fat (in the form of ketones). This happens when the body reaches low levels of glucose.

The ketogenic or “keto” diet attempts to induce this state for an extended period of time by severely limiting carb intake so that there’ll be less glucose in one’s body — forcing the body to switch its fuel source. 

If you are trying to keep your blood sugar levels balanced, the ketogenic diet can help. By lowering carb intake, you are essentially lowering your glucose intake.

Important Health Markers for the Ketogenic Diet 

If you are setting out on a ketogenic diet, it's important to know which health markers can help guide you in the right direction. The first being ketones. Ketones are water-soluble molecules that live in the body. These chemicals are made in the liver and work as a metabolic response to ketosis.

In order to have ketones in your bloodstream, your body must be in a state of ketosis. Our bodies typically rely on glucose as energy, but when we are in ketosis, we are provided with ketones as an alternative. 

Having ketones in your bloodstream is a good thing. The only real danger of ketones is when you are diabetic and have a high amount, leading to something called diabetic ketoacidosis (DKA). 

Aside from measuring ketones, another marker that can be useful to track progress is the glucose ketone index (GKI). This index is calculated using a formula to determine if your body is in ketosis. 

Lastly, your blood glucose levels can be used as ketosis markers as well.

Optimal Blood Glucose Level for Ketosis

optimal blood glucose level for ketosis: glucose monitoring pod

You’ve likely heard that your blood glucose levels can be indicators of insulin resistance or high blood sugar, which can lead to pre-diabetes and Type 2 diabetes. But measuring your blood sugar levels can also help you in managing ketosis. 

Your blood sugar levels won’t tell you if you’re in ketosis, keeping them balanced is important for staying in ketosis. 

To keep them balanced, you’ll want your blood sugar to stay within the normal levels. According to the American Diabetes Association, these are:

  • Fasting blood sugar (morning, before eating your breakfast): 100 mg/dL and below
  • One hour after a meal: 90-130 mg/dL
  • Two hours after a meal: 90-110 mg/dL
  • Five or more hours after a meal: 70-90 mg/dL
  • HbA1c: 5.7% and below

Optimal Ketone Levels and How to Measure Them

Ketone levels are important because they are a marker of ketosis. There is a range of ways to test them that can all be done in the comfort of your home. 

When it comes to actual ketone levels, the target measurements range depending on what your goal for the ketogenic diet is. 

If you are trying to lose weight, then having a ketone level of 0.5 mmol/L to 1.0 mmol/L is key. As you move from losing weight to maintaining weight loss, you can aim for 1.0 mmol/L to 3.0 mmol/L. 

On the other hand, if you are on a ketogenic diet for more therapeutic benefits, aim for a ketone level between 3.0 mmol/L and 5.0 mmol/L.

Testing Your Ketone Levels 

There are three different types of ketones, but the most prevalent one is beta-hydroxybutyrate,  which is what most blood ketone tests check for.

There are three common methods of measuring blood ketone levels. These include urine strips, blood ketone meters, and breath ketone measures. You can also get a blood test from your doctor’s office.

1. Urine Strips

With urine strips, you use a simple urine test to measure levels. You use them when you go to the bathroom, and they will tell you the levels of Acetoacetate (AcAc) in your urine. Acetoacetate (AcAc) and beta-hydroxybutyrate (BOHB) are two different ketones that are found in the urine. This test specifically looks for AcAc. This is an easy and affordable way to check your ketone levels and see if you are on the right track on your keto diet. 

2. Blood Ketone Meter 

If you are familiar with blood glucose meters, this is similar. When you use a blood ketone meter, you prick your finger with a lancet, allow a drop of blood to accumulate, and let it drop on the provided strips. While this is one of the most accurate methods to measure ketone levels, it can get pricey. These test strips usually run around $3-$5 per strip. 

3. Breath Ketone Meter 

Last but not least, this is a meter that works when you blow into a small machine. If you're not big on blood, this can be a great alternative to the blood ketone meter. This method typically checks the ketone acetone. Acetone is one of the ketones found in the human body, and also the smallest ketone. It’s not as common to test for when compared to Acetoacetate (AcAc) and beta-hydroxybutyrate (BOHB) because it is the least abundant ketone. 

4. Blood Test Through a Doctor

You can also get a blood test done in your doctor's office, which is a good option if it is covered by healthcare and you are only looking to check it once. 

Using the Glucose Ketone Index 

Avocado salad in a bowl

The Glucose Ketone Index, most commonly referred to as GKI, is a formula that details the ratio of ketones to blood glucose in your blood. This helps people track their level of ketosis, alongside metabolic health

To determine your GKI, you’ll need to start by knowing your blood glucose level and your ketone level. The best way to measure your blood sugar is by wearing a continuous glucose monitor (CGM). You can measure your ketones using one of the methods we listed above. 

You can use an online calculator to determine your GKI, or you can calculate it yourself using the following formula: [Glucose reading (mg/dL) / 18] / Ketone Reading (mmol/L) = GKI 

For instance, let’s say your blood glucose reading is 100 and your ketone level is 1.8. You would divide 100 (blood glucose) by 18 to get 5.56. You’d then divide 5.56 by 1.8 (ketone level). This would give you a GKI of 3.09.

What Glucose Ketone Index Results Mean

Once you calculate your GKI number, you can determine what your results mean:  

  • If your number is greater than or less than one, you're in the highest form of ketosis. 
  • If your number is 1-3, then you are in a high form of ketosis. 
  • If your number is 3-6, then you are at a moderate level.
  • If your number is 6-9 you are at a low level of ketosis. 
  • If the number is 9 or greater, you are not in ketosis. 

What Is the Keto Flu?

optimal blood glucose level for ketosis: stressed man holding the bridge of his nose

The keto flu, also referred to as the carb flu, is a phenomenon that happens at the onset of the keto diet. As your body adapts to a deficit of carbohydrates, it starts to rely on ketones instead of glucose for energy. Normally, when your body is devoid of glucose, it relies on fat storage for energy, but when you are in ketosis, it goes to the ketones. 

This switch can cause your body to experience symptoms quite similar to the actual flu. 

Symptoms of the Keto Flu

  • Digestive problems (diarrhea, constipation, etc.)
  • Headache
  • Irritability and mood changes
  • Vomiting
  • Dizziness
  • Poor concentration and memory
  • Fatigue
  • Poor performance
  • Difficulty sleeping
  • Sugar cravings

These side effects occur because of the sudden drop of glucose in your system. However, these symptoms are normally temporary because your body will eventually get used to the new glucose level. Still, some people may find these symptoms intolerable, and there are supplements available just to address the keto flu.

Keto Flu vs. Low Blood Sugar: Know the Difference 

When it comes to the keto flu, the symptoms are comparable to having low blood sugar. The difference is the keto flu typically lasts a few days, while low blood sugar comes in waves. 

If you start the keto diet and you experience these symptoms, it can be useful to monitor your blood sugar levels to make sure they are not dropping too low.

Monitor Your Levels for Keto Success

When you want to measure your success on the ketogenic diet, you need to know if you’re in ketosis. You can do this by using your blood sugar level and your ketone level to determine where you are on the Glucose Ketone Index.

While monitoring your ketone levels can be beneficial in determining your GKI, it's not necessarily something you have to monitor all the time. Most people on the ketogenic diet stick to monitoring ketones once or twice a month, whereas a continuous glucose monitor can be helpful around the clock to show optimal blood glucose levels.

In addition to helping you on your keto journey, using a continuous glucose monitor can keep you on track for long-term and short-term health goals. You can use the information to personalize your diet and activities based on how your body uniquely reacts.

Sign up today for Vital to begin understanding your blood sugar levels and receive personalized recommendations about exercise, food, and daily habits.

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