Measuring blood sugar on a low-carb diet —

Diabetes has no cure. It can be managed, but it can’t ever be cured. The good news is that it can be managed well. The bad news is that there is no one diet that is perfect for everyone. Instead, there are multiple diets that, depending on what your blood sugar goals are, can all work very well.

Low-carb diets are all the rage these days, and most people who want to try the diet for themselves start by downloading an app and testing their blood sugar level on a regular basis. But are these apps as accurate as they seem? Does the text they display really reflect what is happening in your blood? And how can you get a better idea of your current levels?

The benefits of a low-carb diet are well documented. The diet offers a plethora of health benefits, including weight loss and improved insulin sensitivity. However, many people don’t know when to stop the diet. While it can be done indefinitely, a low-carb diet is often followed by a plateau in weight loss where the dieter is unable to lose any more weight.. Read more about why is my blood sugar high on a low carb diet and let us know what you think.

Updated on June 17, 2021 by, with medical review by

You may have purchased a blood sugar meter after receiving a worrisome diagnosis of pre-diabetes or diabetes. Perhaps one of these illnesses runs in your family. Perhaps you’re just interested about how food affects your blood sugar levels and are ready to give up a few drops of blood to find out.

If you’ve never tested your blood sugar before, don’t worry; it’s a straightforward procedure.

You may have been monitoring your blood sugar for years if you’ve had diabetes for a long time. However, understanding the changes that occur after converting to a low-carb or keto diet may take some time.

Testing your blood sugar, whether you’ve done it before or not, may help you better determine which dietary adjustments decrease your blood sugar over time. It may also assist you in identifying meals that cause blood sugar to rise.

Disclaimer: This tutorial is intended to teach you the fundamentals of blood glucose testing. It is not intended to be taken as medical advice. Low blood sugar has the potential to be life-threatening. If you have low blood sugar and are experiencing the symptoms mentioned in this article, the fastest treatment is to eat or drink sugar or carbohydrates, and then speak with your doctor about the following steps.

1. Where to Begin

There are many different blood sugar meters (also known as glucose meters or glucometers) on the market, and the majority of them are reasonably priced.

Make sure, however, that your meter’s test strips are both cheap and readily accessible. The true cost of blood sugar testing is the cost of the strips, which are only good for one usage and expire after a set period of time.

A lancet, which has a short, tiny needle that can puncture your finger swiftly and (nearly) painlessly, is required in addition to a meter and strips. Lancets are extremely cheap and are thrown away after each usage. A lancet and approximately a dozen new needles are included with most blood sugar meters.

How to Take Blood Sugar Readings

You should read and follow the instructions that came with your blood sugar meter. The basic approach for most meters is as follows:

  • Place a test strip in your blood sugar meter with clean hands.
  • To draw a drop of blood, prick the side of a finger with the lancet.
  • Place the test strip’s tip on a drop of blood.
  • The blood sugar meter will give you a reading within a few seconds.

Many blood sugar meters will record your blood sugar levels for many days or weeks. Even if your meter saves these readings, it’s a good idea to write down the date, time, and other details to discuss with your healthcare practitioner or save for yourself. To keep track of your readings, use a notepad, a computer spreadsheet software, or an app like this one.

An alternative to fingerstick and venous blood glucose testing is an A1C home test kit. This home tester kit allows you to self-check average blood glucose level for the past three months, measuring the red blood cell percentage with sugar-coated hemoglobin. It can do so much for chronic disease management, enabling you to better adjust your care plan, especially if you have diabetes.

Moreover, AC1 home test kit results are 99% correlated to fingerstick and venous blood draws.

Look for an AC1 home tester kit that’s IFCC-traceable, NGSP-certified, and CE-marked for self-test use for safety.

When should you check your blood sugar?

If your healthcare practitioner has given you particular instructions on when to test your blood sugar, make sure you follow them.

Before eating, many individuals check their blood sugar levels first thing in the morning. A blood sugar measurement at this time of day is termed a “fasting blood sugar” since no meal has been eaten for at least 8-10 hours. It’s recommended to check this every day at the same time.

You may also check your blood sugar before or after a meal (pre-meal or preprandial level) (a post-meal or postprandial level). If you’ve been told to check your blood glucose after a meal at a certain time interval, you should start timing as soon as you start eating.

Exercise is essential for people with diabetes. If you’re following a personal or prescribed workout plan, don’t miss checking your blood glucose every 30 minutes. That way, you can check if your blood sugar rises or falls during your routine. Your aim is to stabilize your blood sugar during workouts for safe and uninterrupted exercise.

Doctors also recommend patients test their blood glucose more often when sick. When a person is sick, the body releases cortisol and other hormones to combat infection, which can increase the blood glucose and insulin requirement. See your doctor or report sick days for proper treatment and blood sugar monitoring to prevent undue diabetes complications, such as vision and renal problems.

2. What is a healthy blood sugar level?

Blood sugar levels that are considered “normal” are based on people who consume a typical American diet. Carbohydrate, the food that tends to increase blood sugar the highest, makes up approximately half of the calories in this diet.

You may have a different “normal” if your carbohydrate consumption is much lower. For additional information, see How a low-carb diet impacts blood sugar readings.

Blood sugar levels after a fast

In those who do not have diabetes, a normal fasting blood sugar level is between 70 and 100 mg/dL (3.9 to 5.6 mmol/L).

Prediabetes, also known as impaired fasting glucose, is defined as fasting blood sugar that regularly decreases in the range of 100 to 125 mg/dL (5.6 to 6.9 mmol/L).

You may have diabetes if your fasting blood sugar is more than 126 mg/dL (7.0 mmol/l) on two consecutive occasions.

If you’re worried about your blood sugar readings, particularly if you’re already on a low-carb diet, read How a low-carb diet impacts blood sugar readings. A few blood sugar readings may not always be enough to give you a complete picture of your health.

Blood sugar levels after a meal

If your healthcare practitioner hasn’t given you particular advice on when to test your blood sugar after a meal, you may try testing it one to two hours after you start eating. Because blood sugar levels may peak at various times, you should pay attention to whichever measurement is the highest.

Your body’s capacity to handle carbs determines how much and how fast your blood sugar level rises after eating.

Blood sugar levels usually peak approximately an hour after beginning a meal in individuals who do not have diabetes. Blood sugar levels in individuals with type 2 diabetes, on the other hand, usually peak two hours after a meal begins. As a result, diabetics are often recommended to check their blood sugar two hours after eating.

A typical post-meal blood sugar level one or two hours after a meal is below 140 mg/dL (7.8 mmol/L), according to the American Diabetes Association. Some doctors and people who are concerned about high blood sugar levels may choose a carb-restricted strategy that aims for a post-meal blood sugar level of 120 mg/dl (6.7 mmol/L) or less.

You may have prediabetes or impaired glucose tolerance if your blood sugar is regularly 140 mg/dL (7.8 mmol/L) or higher but less than 200 mg/dL (11.1 mmol/L) two hours after starting a meal.

You most likely have diabetes if your blood sugar levels are regularly 200 mg/dL (11.1 mmol/L) or above two hours after starting a meal.

You may have a medical issue that necessitates a visit to a healthcare professional if your fasting or post-meal blood sugar levels are persistently higher or lower than usual.

If your blood sugar levels suddenly change from “normal” to “not normal” after you receive a new meter or test strip container, double-check your meter and strips to be sure they’re getting correct readings. When a result is significantly different from what was anticipated, take three measurements and average them.

Chart of blood glucose levels

Before you think that your blood sugars are too high or too low, you should do each test on at least two different times. Consult your healthcare practitioner if you have any concerns regarding your blood sugar levels.

3. What to do if your blood sugar levels aren’t as high as they should be

Hypoglycemia is defined as blood sugar levels below 70 mg/dL (3.9 mmol/L). Heart palpitations, jitteriness, irritability, tiredness, and sweating are all symptoms of hypoglycemia.

If you have diabetes and your medication does not match your carbohydrate consumption, you may have low fasting blood sugar levels. As a result, it’s critical to inform your doctor that you’re on a low-carb diet so that your prescription may be adjusted to match your carb consumption.

Low fasting blood sugar levels in individuals who don’t have diabetes may be the consequence of a severe underlying medical issue such an eating disorder or a tumor. Consult your healthcare practitioner if your fasting blood sugar is low and you are not taking diabetic medication.

Reactive hypoglycemia is a term for low blood sugar levels after eating. This may happen to individuals with diabetes or those who have normal fasting blood sugars. The treatment will be determined by the underlying reason. However, if you have low blood sugar and are experiencing symptoms, you may temporarily improve your situation by consuming something high in carbohydrates or sugar.

In individuals who are extremely insulin sensitive or have lost a lot of weight, a high-carb diet may induce reactive hypoglycemia. In individuals who have had weight-loss surgery, a low-carb, high-protein diet has been shown to ameliorate reactive hypoglycemia.

Polycystic ovarian syndrome (PCOS), a disease that may be effectively treated with a low-carb diet in certain instances, can also cause reactive hypoglycemia.

4. What to do if your blood sugar is higher than it should be

You may have prediabetes or diabetes if your fasting or post-meal blood sugar levels are persistently higher than usual. If you think you have diabetes or prediabetes, make an appointment with your doctor as soon as possible.

Aside from high blood glucose, diabetes may cause increased thirst and urination, extreme tiredness, and an insatiable appetite. See our diabetes signs and symptoms page for more information.


5. Tailoring your diet to your blood sugar reaction

There are measures you may do to lower your blood sugar levels in addition to visiting your healthcare professional. You may be able to identify which items are troublesome if you check your blood sugar after meals and keep note of those readings, as well as the kinds and quantities of food you ate.

Although consuming high-carb meals is generally associated with a rise in blood sugar, not all carbohydrates are created equal when it comes to increasing blood sugar. Because starchy meals rapidly break down into glucose (sugar), certain starchy foods may have a considerably higher effect on blood sugar than you would anticipate.

Even if a banana is sweeter than a baked potato, the potato may have a greater effect on blood sugar levels.

Because high-carb meals have the greatest effect on blood sugar levels, reducing them makes sense regardless of your diet. In a 2019 study on diabetes nutrition, the American Diabetes Association addressed this argument.

It’s sometimes better to make incremental adjustments. Eating better: six steps down carb mountain is a strategy that will help you reduce your food consumption one step at a time.

If you have type 1 or type 2 diabetes, our guide to the best foods for diabetes may help you make decisions that may decrease your need on blood sugar medicines.

Although carbs are the most common cause of elevated post-meal blood sugar, eating a lot of protein may also cause blood sugar to spike. Our protein guide may help you figure out how much protein to consume while keeping your blood sugar in control.

Other low-carb meals may also cause a rise in blood sugar response. Blood sugar levels were greater after caffeinated coffee was eaten with meals containing either quickly digested or slowly digested carbohydrates in one research than after the same meals without caffeine.

If a meal or beverage seems to be causing your blood sugar to spike excessively, consider eliminating it from your diet for a few days to see if you notice a change.


6. Blood sugar levels may be measured in a variety of methods.

Using a glucometer to check your blood sugar levels isn’t the only method to do so. Your healthcare practitioner may also use other tests to monitor your blood sugar levels, such as hemoglobin A1c (HbA1c) and an oral glucose tolerance test (OGTT). You may be able to get a continuous glucose monitor if you’re very fortunate (CGM).

HbA1c is a measure of your average blood sugar levels over time, giving you a sense of how well you’ve managed your blood sugar in the previous two or three months. The HbA1c test is the most frequent test for type 2 diabetes diagnosis.

HbA1c testing and blood sugar tests, on the other hand, don’t always agree. HbA1c values are frequently ineffective in identifying those who would otherwise be diagnosed with diabetes based on blood sugar levels.

If your HbA1c is less than 5.7 percent, it is considered normal. If your HbA1c is more than 5.7 percent but less than 6.5 percent, you may have prediabetes. If your HbA1c is 6.5 percent or above, you may have diabetes.

Normal 5.7 percent (38.8 mmol/mol) or less
Prediabetes Between 5.7 and 6.4 percent (38.8 and 46.4 mmol/mol)
Diabetes 6.5 percent or above (47.5 mmol/mol)
Taking a “wary” attitude 36.0 mmol/mol (less than 5.4 percent)

See our complete guide to understanding HbA1c for more information on HbA1c readings and how they relate to the blood sugar levels you record with your glucometer.

When it comes to detecting prediabetes or diabetes, an oral glucose tolerance test (also known as an OGTT) may be more accurate. Two hours after consuming 75 grams of glucose, it tests your blood sugar. An OGTT may not be a helpful test for someone on a long-term low-carb or ketogenic diet since it involves drinking a substantial sugar solution (more on this in the next section).

A continuous glucose monitor (CMG) is a wearable device that constantly monitors blood glucose levels, as the name implies. They’re a highly precise method to test blood sugar throughout the day, despite the fact that they’re costly and generally only authorized by insurance for type 1 diabetes. This makes it simple to observe post-meal fluctuations and obtain a daily average blood sugar level.

7. Blood sugar readings with a low-carb diet

If you’re on a low-carb diet, you may notice that certain blood sugar testing methods don’t give you “normal” results.

Fasting blood sugar levels, for example, may be somewhat higher than usual. It’s possible that “adaptive glucose sparing” and “the dawn phenomena” are to blame. Because your liver is producing additional glucose to prepare your body for the day, your fasting blood sugar levels may be high.

If you’re worried about these numbers, ask your doctor to examine your HbA1c, which measures your average blood sugar management over a period of two to three months (more on this below).

Your HbA1c will likely be lower than your fasting blood sugar levels if you’re on a low-carb diet, since your blood sugar levels don’t rise as much after meals.

An OGTT may erroneously identify you with diabetes if you’ve been on a low-carb diet for a long period. You may experience an increased blood sugar reaction to the glucose drink since your body is fat adapted and no longer uses sugar as its primary fuel. If this happens, you may fail the test and be diagnosed with diabetes while you don’t have the disease.

If your doctor has prescribed an OGTT test and you wish to do it, begin eating carbohydrates and sugar three days before to the test.

If you’re on a ketogenic diet and your ketones are high, your blood sugar may naturally be 70 mg/dL (3.9 mmol/L) or somewhat lower. Because ketones are fuelling your body, you are unlikely to experience classic hypoglycemia symptoms like shakiness or lightheadedness.

Taking your blood sugar may be a quick and easy method to learn about the impact different meals have on your body. It’s essential to remember, though, that your blood sugar level is simply a number, just like your weight. Panicking when your fasting blood sugar is 102 mg/dL (5.7 mmol/L) in the morning adds to your day’s stress, which isn’t good for your health!

Make good use of your glucometer as another tool in your health toolkit.

/ Dr. Adele Hite, MPH, RD

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This article will discuss how to test blood glucose levels for someone on a low-carb diet.. Read more about is glucose keto-friendly and let us know what you think.

Frequently Asked Questions

How a low carb diet affects blood sugar measurements?

A low carb diet can have a significant impact on blood sugar levels. When you eat carbohydrates, your body releases insulin to help regulate blood sugar levels. If you are not eating carbs, then your body will release less insulin and your blood sugar may rise too high or too low.

Why is my blood sugar so high when Im not eating any carbs?

Your blood sugar is high because you are not eating any carbs.

What should blood sugar levels be on keto?

The blood sugar levels on keto should be between 70-130.

Related Tags

This article broadly covered the following related topics:

  • why is my blood sugar high on a low carb diet
  • how to raise blood sugar on keto
  • i eat almost no carbs and my blood sugar is still high
  • adaptive glucose sparing
  • can a low carb diet cause elevated blood sugar

Una is a food website blogger motivated by her love of cooking and her passion for exploring the connection between food and culture. With an enthusiasm for creating recipes that are simple, seasonal, and international, she has been able to connect with people around the world through her website. Una's recipes are inspired by her travels across Mexico, Portugal, India, Thailand, Australia and China. In each of these countries she has experienced local dishes while learning about the culture as well as gaining insight into how food can be used as a bridge between different cultures. Her recipes are often creative combinations of traditional ingredients from various different cuisines blended together to create something new.