Blood Sugar Control On A Keto Diet

A ketogenic diet is one that is very low in carbohydrates and high in fats. The body's primary source of energy is glucose, which mainly comes from carbohydrates. When the body is deprived of carbohydrates, it switches to ketosis, a metabolic state in which the body breaks down fats for energy, releasing ketones. Ketosis is a normal process and can be induced by exercise or the keto diet. However, it is important to monitor blood sugar and ketone levels, especially for those with diabetes, as high levels of ketones can lead to a dangerous condition called ketoacidosis.

The optimal ketone and blood sugar levels for ketosis are between 1.0 mmol/L and 3.0 mmol/L. A light nutritional ketosis is achieved with levels between 0.5 mmol/L and 1.0 mmol/L.

Fasting blood sugar levels in a non-diabetic person are generally between 70 and 100 mg/dL (3.9 to 5.6 mmol/L). Levels between 100 and 125 mg/dL (5.6 to 6.9 mmol/L) are considered prediabetes, and levels above 126 mg/dL (7.0 mmol/L) on two separate occasions may indicate diabetes.

Monitoring blood sugar and ketone levels can help identify dietary changes that lower blood sugar and specific foods that raise it.

What is blood glucose?

Blood glucose, also known as blood sugar, is the amount of sugar circulating in your blood. It is a form of sugar derived from the food you eat, which your body uses for energy. As it travels through your bloodstream to your cells, it is called blood glucose or blood sugar. Glucose is a simple sugar that cells in the body can easily use to power themselves.

The body breaks down other carbohydrates into glucose for energy, storing any excess glucose it does not need. For balance, people need enough glucose to fuel cells, but not so much that there are consistently high amounts in the bloodstream. Blood glucose monitoring gives people insight into the amount of sugar that the blood is transporting at that time.

Glucose comes from the food you eat, particularly foods that are rich in carbohydrates, including bread, potatoes, and fruit. As you eat, food travels down your oesophagus to your stomach, where acids and enzymes break it down into tiny pieces, and glucose is released. From there, it goes into your intestines, where it is absorbed and passes into your bloodstream. Insulin then helps glucose get inside your cells.

Your body is designed to keep the level of glucose in your blood constant. Special cells in your pancreas called beta cells monitor your blood sugar level every few seconds. When your blood glucose rises after you eat, the beta cells release insulin into your bloodstream. Insulin acts like a key, unlocking muscle, fat, and liver cells so glucose can get inside them.

Most of the cells in your body use glucose along with amino acids (the building blocks of protein) and fats for energy. But blood sugar is the main source of fuel for your brain. Nerve cells and chemical messengers there need glucose to help them process information. Without glucose, your brain wouldn't be able to work well.

After your body has used the energy it needs, the leftover glucose is stored in little bundles called glycogen in your liver and muscles. Your body can store enough to fuel you for about a day. If you haven't eaten for a few hours, your blood glucose level drops. Your pancreas stops churning out insulin. Alpha cells in your pancreas begin to produce a different hormone called glucagon, which signals your liver to break down stored glycogen and turn it back into glucose.

Blood glucose levels can change throughout the day. After eating, levels rise and then settle after about an hour. They are at their lowest point before the first meal of the day. Typically, a person's fasting blood glucose level should be below 99 milligrams per decilitre (mg/dL). Keeping blood glucose levels within a healthy range can reduce the risk of diabetes and heart disease.

How to test blood sugar levels

To test your blood sugar levels, you can use a blood glucose meter or a continuous glucose monitor (CGM). Here is a step-by-step guide on how to use a blood glucose meter:

• Wash your hands.
• Insert a test strip into the meter.
• Use a lancing device on the side of your fingertip to get a drop of blood.
• Touch and hold the edge of the test strip to the drop of blood and wait for the result.
• Your blood glucose level will appear on the meter's display.

It is important to note that all meters are slightly different, so always refer to your user's manual for specific instructions. With some meters, you can also use your forearm, thigh, or the fleshy part of your hand. Additionally, there are spring-loaded lancing devices that make the process less painful.

If you are testing your blood sugar levels at home, it is important to log your results and bring them to your healthcare provider. They can help you understand your body's response to your diabetes care plan and make any necessary adjustments.

For those on the keto diet, testing your blood sugar levels can provide insights into your body's response to specific foods. It is recommended to test your blood sugar at the same time each day, usually after an overnight fast of around 12 hours. This guarantees that your body is always in a similarly fasted state.

It is worth noting that blood glucose levels are just one aspect of metabolic health. Other factors to consider include triglycerides, high-density lipoprotein (HDL) cholesterol, blood pressure, and waist circumference.

What is a normal blood sugar level?

Blood glucose, or blood sugar, is the amount of sugar circulating in your blood. Your blood sugar will rise and fall when you eat food. This is a normal process, but how high your blood sugar spikes can depend on the food you eat. For example, a high-carb meal will spike your blood glucose much more than a low-carb, high-fat meal.

Higher than normal blood glucose levels can cause damage to the body, increasing the risk of diabetes and heart disease. Doctors even use a blood glucose test to diagnose type 2 diabetes.

According to the American Diabetes Association (ADA), a normal fasting blood sugar level (measured before eating) in someone who does not have diabetes is generally between 70 and 100 mg/dL (3.9 to 5.6 mmol/L). Fasting blood sugar that consistently falls in the range of 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is considered prediabetes, which can lead to type 2 diabetes if not addressed. If your fasting blood sugar is above 126 mg/dL (7.0 mmol/l) on two separate occasions, then you may have diabetes.

Post-meal blood sugar levels (measured one to two hours after eating) in a non-diabetic person typically peak about an hour after starting a meal and should be below 140 mg/dL (7.8 mmol/L). However, some people may prefer to target a post-meal blood sugar level of 120 mg/dl (6.7 mmol/L) or lower to be cautious. If your blood sugar is consistently above these levels, you may have prediabetes or diabetes.

It's important to note that these ranges may not apply if you are on a low-carb or ketogenic diet, as your body adapts to using fat instead of glucose for energy. In this case, your fasting blood sugar levels may be slightly above normal due to "adaptive glucose sparing" and "the dawn phenomenon". Your healthcare provider can help you interpret your blood sugar levels and determine if further evaluation is needed.

How to measure blood glucose

You can measure your blood glucose levels using a blood sugar meter (glucometer), which is a simple and inexpensive device. Most blood sugar meters use a lancet to prick your finger and draw a drop of blood, which is then placed on a test strip that provides a reading. You can also measure your blood glucose levels continuously throughout the day using a wearable device called a continuous glucose monitor (CGM).

Factors affecting blood sugar levels

In addition to diet, other factors such as exercise, sleep, and stress can impact your blood sugar levels. If you have diabetes, certain medications and lifestyle changes can help lower your blood sugar levels. It's important to work with your healthcare provider to determine the best approach for managing your blood sugar levels.

How does a keto diet impact blood glucose?

The ketogenic diet is a metabolic state that can only be achieved when the body is deprived of carbohydrates. It is a low-carb, high-fat diet that puts the body into a state of ketosis, where it burns fat for energy instead of glucose. This has several implications for blood glucose levels:

Lower glucose trends

Since the keto diet restricts carbohydrates, the primary source of glucose, it is expected that blood glucose levels will be lower and more stable. This is indeed the case for most keto dieters, with average glucose levels hovering between 70-90 mg/dL.

Elevated fasting glucose levels

Prolonged adherence to a strict keto diet can lead to elevated fasting glucose levels, a natural adaptation known as "glucose sparing." This occurs as the body ensures a sufficient amount of glucose is present for organs that require it. While this may be concerning, current research suggests it is not necessarily detrimental to health, as long as other health metrics such as glycemic variability, fasting insulin, HDL, triglycerides, and liver enzymes remain within healthy ranges.

High glucose spikes to small amounts of carbs

Keto diets can lead to a temporary physiological insulin resistance, where the body overreacts when carbohydrates are introduced, resulting in slightly higher glucose responses to small amounts of carbs. This is because muscles, which typically prefer glucose, start to utilize fatty acids for fuel instead, leading to larger glucose elevations when carbs are consumed.

Identifying trigger foods

The impact of specific foods on blood glucose levels can vary significantly from person to person. A continuous glucose monitor (CGM) can help identify trigger foods that cause elevated glucose spikes and guide dietary adjustments to maintain ketosis.

Testing carb and protein thresholds

The keto diet does not require a strict restriction of carbohydrates. By testing carb thresholds through gradual increases in carbohydrate intake while monitoring ketone and glucose values, individuals can determine their personal limit for carb consumption while maintaining ketosis. Similarly, testing protein thresholds can help identify excessive protein intake, which can lead to a gradual rise in glucose levels.

Other considerations

The keto diet may cause elevated fasting glucose levels due to "adaptive glucose sparing" and "the dawn phenomenon," where the liver produces extra glucose in preparation for the day. Additionally, for those on a long-term keto diet, an oral glucose tolerance test (OGTT) may lead to a false diagnosis of diabetes due to an exaggerated blood sugar response to the glucose drink.

How to monitor blood sugar on keto

Ketosis is a metabolic state that can only be achieved when the body is deprived of carbohydrates. When you're eating a ketogenic diet, your blood sugar is regulated thanks to such a low daily carbohydrate intake.

However, blood glucose does not indicate whether you're in ketosis. But it can be correlated with the ketone levels in your body. It's also an indicator of your insulin sensitivity or lack thereof. This is why blood glucose levels are used as one of the indicators of developing type 2 diabetes, which is strongly tied to insulin resistance.

How to test your blood sugar

Blood glucose monitors are easy to find and relatively affordable, at least compared to blood ketone monitors. Unlike ketone monitors, blood glucose monitors provide a relatively immediate picture of how your body is responding to specific foods, meals, and activities, such as workouts.

Consider testing your blood sugar at the same time as your ketones to get a more holistic perspective of what's happening in your body. For instance, is that new low-carb protein bar going to keep you in ketosis without spiking your blood sugar? There's really only one way to find out: test both ketones and blood glucose.

When to test your blood sugar

Unless you're trying to test how your body responds to very specific things, such as a certain sweetener, there are no rules on when you need to test. The rule of thumb is to measure at the same time each day. That will guarantee that your body is always in a similarly fasted state.

According to the Mayo Clinic, a fasting blood sugar level under 100 milligrams per decilitre is healthy. Your blood sugar following food (even ingesting pure sugar) should not exceed 125 milligrams per decilitre, as this is a sign of prediabetes.

Factors that may impact your blood sugar reading

Some of the things that can spike your blood sugar (and affect your reading) include certain non-caloric sweeteners and a lack of exercise or activity. Notice that carbs weren't on that list? Of course, they raise your blood sugar. But this list was to give you an idea of the things that can affect your blood glucose reading even when you're following a keto diet.

Similarly, there are a few things that can lower your blood sugar. These include alcohol. Note: we do not recommend drinking alcohol to lower your blood sugar.

Measuring blood sugar can be useful for those following a keto diet. But unless you're diabetic, you don't really need to do it. Think of measuring blood sugar as a tool, not a necessity. It should not be a priority unless you're curious about it.

Frequently asked questions