Written by Angela Reviewed by Daniel

How to Track Blood Sugar on Keto (And What the Numbers Mean)

Following a ketogenic diet isn’t just about cutting carbs; it’s about understanding how your body responds to different foods, activities, and metabolic states. One of the most overlooked aspects of keto is blood sugar monitoring. While most people focus on ketone levels, tracking blood glucose can provide deeper insights into how your body handles food and whether you’re truly optimising your health.

Keeping an eye on your blood sugar can help you personalise your diet, detect hidden carbohydrates, and even understand how your body reacts to stress, sleep, and exercise. But what should your numbers look like? When should you test? And how do blood glucose and ketosis interact?

This guide will take you through the essentials of blood sugar monitoring on keto, explaining the numbers, the best testing practices, and what factors influence your readings. Whether you’re a keto veteran or just starting, tracking blood glucose can be a powerful tool for achieving your goals.

Table of Contents

Understanding Blood Glucose

Blood glucose refers to the concentration of sugar in your bloodstream, serving as a primary energy source for your body’s cells. Typically, blood sugar levels fluctuate based on food intake, with high carbohydrate meals causing more significant spikes compared to low carbohydrate, high fat meals. Consistently elevated blood glucose levels can lead to health issues such as type 2 diabetes and heart disease.

The Link Between Blood Glucose And Ketosis

Ketosis is a metabolic state where the body utilises fat as its main energy source due to limited carbohydrate availability. While blood glucose levels don’t directly indicate ketosis, they are closely linked.

A ketogenic diet typically leads to more stable and lower blood glucose levels, which can enhance insulin sensitivity. Monitoring these levels helps assess how different foods and activities impact your metabolism and ketone production.

Reasons To Monitor Blood Glucose On A Keto Diet

There are three reasons why you should monitor blood glucose on a keto diet which are;

Understanding How Food Affects Your Body
Testing your blood glucose allows you to understand how specific foods affect your body. For instance, eating certain vegetables or fruits might impact your ketosis; monitoring helps determine your personal carbohydrate tolerance.
Finding Hidden Carbohydrates
Some ingredients, including certain artificial sweeteners, can cause unexpected blood sugar spikes. Regular monitoring can help identify such culprits, enabling you to make informed dietary choices.
Managing Dietary Deviations
If you occasionally eat higher carb meals, tracking blood glucose can provide insights into how quickly your body recovers and returns to ketosis, informing future decisions about food intake.

How To Measure Blood Glucose

Monitoring your blood glucose (or blood sugar) levels is a key part of managing your health, particularly if you have diabetes, follow a low carb keto diet, or want to keep an eye on your overall well being.

Blood glucose monitors are widely available and simple to use. They require a tiny drop of blood, usually from your fingertip, to give an immediate reading. These readings help you understand how your body responds to food, exercise, stress, and medication.

For a more complete picture, you might also want to measure blood ketones. Ketones are chemicals produced when your body burns fat for fuel instead of glucose. Tracking both glucose and ketones together can be especially useful if you’re following a ketogenic or low carb diet, as it helps you see how your body is adapting and whether you’re in ketosis.

Understanding Blood Glucose Readings

Blood glucose levels are measured in millimoles per litre (mmol/L). What’s considered normal varies depending on when you last ate.

General Blood Glucose Ranges

Timing	Normal Range	High (needs attention)	Low (hyperglycaemia)
Before food (fasting)	4.0 to 5.9 mmol/L	More than 7.0 mmol/L	Less than 4.0 mmol/L
90 minutes after eating	Below 7.8 mmol/L	More than 11.0 mmol/L	Extremely rare after eating
Random reading	Typically below 8.5 mmol/L	More than 11.0 mmol/L	Less than 4.0 mmol/L

High Blood Sugar (hyperglycaemia)

If your readings are frequently above 11.0 mmol/L, this could be a sign of diabetes or poor glucose control. Over time, high glucose levels can lead to complications such as nerve damage, vision problems, and heart disease.

Low Blood Sugar (hypoglycaemia)

A reading below 4.0 mmol/L can cause symptoms like;

Dizziness
Shaking
Sweating
Confusion
Fainting

If untreated, severe low blood sugar can be dangerous. Eating a small, fast acting carbohydrate (like glucose tablets or fruit juice) can help raise levels quickly.

Good Vs Bad Readings, What to Look For

Here’s what to look out for;

Good readings
Staying within the normal range as much as possible, with minimal spikes after meals.
Bad readings
Frequent highs (above 11.0 mmol/L) or lows (below 4.0 mmol/L) suggest your diet, exercise, or medication may need adjustment.

If you’re regularly seeing high or low readings, it’s worth discussing with a healthcare professional who can guide you on the best steps to take.

The Role Of Blood Ketones In Monitoring Health

If you’re tracking blood ketones alongside glucose, it can provide extra insight, especially if you’re on a ketogenic diet. Here’s what your ketone readings might indicate:

Ketone Level (mmol/L)	What It Means
0.0 to 0.5	Not in ketosis (your body is using glucose for fuel)
0.5 to 3.0	Nutritional ketosis (your body is burning fat which is normal on a keto diet)
3.0+	High ketone levels, this might be normal for some keto dieters but could also indicate ketoacidosis if you have diabetes, if you’re not sure contact a GP
Over 5.0	Possible diabetic ketoacidosis (DKA) this is dangerous and needs urgent medical assistance

Tips For Accurate Blood Glucose Testing

To get the best results from your blood glucose monitor:

Wash Your Hands Before Testing
Residue from food or lotions can affect readings.
Use A Fresh Test Strip For Each Measurement
Old or expired strips may give inaccurate results.
Test At Consistent Times
Measuring at the same times each day (e.g., before meals and two hours after) helps track trends.
Keep A Log Of Your Readings
Writing down your results alongside what you ate and any symptoms can help you spot patterns.
Calibrate Your Meter If Needed
Some monitors require periodic calibration for accuracy.

Measuring blood glucose is a simple yet powerful way to manage your health. Whether you have diabetes, are following a low carb diet, or just want to monitor your body’s response to food, regular testing can provide valuable insights. By understanding what your readings mean and how to respond to them, you can take control of your health and make informed decisions about your diet and lifestyle.

Optimal Timing For Testing

Consistency is key when monitoring blood glucose. Testing at the same time each day, preferably in a fasted state (such as before breakfast), ensures easy comparability of readings.

Additionally, testing before and after meals can reveal how specific foods influence your blood sugar levels.

Interpreting Blood Glucose Readings

According to experts, a fasting blood sugar level below 100 milligrams per decilitre (mg/dL) is considered healthy. Levels after eating (Postprandial) should not be higher than 125 mg/dL, as higher readings might be indicative of prediabetes.

To assess your metabolic state, you can calculate the Glucose Ketone Index (GKI) by dividing your blood glucose level (in mmol/L) by your blood ketone level. A GKI of 9 or lower is typically associated with ketosis.

Factors Influencing Blood Glucose Levels

There are a number of factors that can affect blood glucose readings, including:

Dietary Intake
Consumption of food, especially carbohydrates, raises blood sugar levels.
Artificial Sweetener
Some artificial sweeteners may impact blood glucose. Notably, a study published in Cell Metabolism found that aspartame could increase insulin levels and the risk of heart attack and stroke in animal testing.
Stress
Raised cortisol levels due to stress can increase blood sugar.
Sleep Patterns
Not enough or interrupted sleep may lead to higher blood glucose levels.
Physical Activity
Regular exercise generally lowers blood sugar.
Fasting
Periods without food intake can reduce blood glucose.
Alcohol Consumption
While alcohol can lower blood sugar, it is not recommended as a method for managing glucose levels.

The Role Of Blood Glucose Monitoring In A Keto Lifestyle

While not mandatory, monitoring blood glucose on a ketogenic diet can provide valuable insights, especially for those aiming to optimise their health or manage conditions like diabetes. It serves as a tool to personalise your dietary approach, ensuring it aligns with your body’s unique responses.

However, it’s essential to focus on overall well being rather than becoming fixated on specific numbers. Maintaining a balanced diet, staying active, and managing stress are equally crucial components of a healthy lifestyle.

So There You Have It

Above is all you need to know about how and why you should monitor blood glucose levels while following a keto diet. Are you on a keto diet? Are you going to start to monitor your glucose levels? Let us know in the comments.

And if you found this helpful, share it with your socials to alert all of your friends to the benefits of glucose monitoring when following a keto diet plan.

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